Ketotifen

updated

Ketotifen is an approved antiallergic: every FDA application is ophthalmic, with eye drops first approved in 1999 and the over-the-counter ALAWAY in 2006, and oral Zaditen is nationally authorized in several EU countries. The off-label use with clenbuterol rests on 1980s and 1990s volunteer and asthma receptor studies, and no study measured fat loss, muscle or performance. A seller's statement that no study used clenbuterol is wrong: a 1990 asthma study combined the two.

Antihistamine

  • FDA first approved ketotifen as ZADITOR eye drops on 2 July 1999; none of the 8 ketotifen fumarate applications in Drugs@FDA is oral.
  • EMA's June 2024 list shows oral Zaditen products nationally authorized in Belgium, Spain, France, Ireland, Italy, the Netherlands, Portugal, and Northern Ireland, all held by Alfasigma.
  • A Cochrane review of 26 double-blind trials (1,826 children with asthma) found more children reduced or stopped bronchodilator use on oral ketotifen (RR 2.39), with sedation 21% versus 12% and weight gain 27% versus 17%.
  • In 36 healthy volunteers, ketotifen completely prevented the terbutaline-induced fall in lymphocyte beta-2 adrenoceptor density, a receptor marker rather than a fat or muscle outcome.
  • A PubMed search on 9 October 2026 for ketotifen with beta-receptor terms returned 116 records; the human work runs from 1984 to 1999, and no human study measured adipose tissue, lipolysis, or skeletal muscle.
  • A PubMed search for ketotifen and clenbuterol returned 2 records, including a 1990 human asthma study, so the claim that no study used clenbuterol is incorrect.

What is ketotifen approved to do?

Every ketotifen application in Drugs@FDA is ophthalmic: eye drops first approved in 1999, the over-the-counter ALAWAY in 2006, and a drug-eluting contact lens in 2022. Oral ketotifen is nationally authorized in several EU countries.

ZADITOR eye drops were first approved under NDA 021066 on 2 July 1999 and are now discontinued. ALAWAY was approved under NDA 021996 on 1 December 2006 and is over the counter; its label covers temporary relief of itchy eyes due to ragweed, pollen, grass, animal hair, and dander in adults and children 3 years and older. A ketotifen drug-eluting contact lens (ACUVUE THERAVISION WITH KETOTIFEN, NDA 022388) was approved on 25 February 2022 and is listed as discontinued. None of the 8 ketotifen fumarate applications is oral, and a search for the oral brand ZADITEN returned no match on 9 October 2026.

EMA's June 2024 list shows Zaditen capsules, tablets, syrup or oral solution, and prolonged-release tablets nationally authorized in Belgium, Spain, France, Ireland, Italy, the Netherlands, Portugal, and Northern Ireland, all held by Alfasigma. The indication wording of these oral products is not stated here. UK Zaditen eye drops are indicated for symptomatic treatment of seasonal allergic conjunctivitis from age 3.

Ketotifen base is C19H19NOS (309.4 g/mol, CAS 34580-13-7). The marketed salt is ketotifen fumarate (C23H23NO5S, 425.5 g/mol, CAS 34580-14-8), and strengths may be stated either way. Supplier oral products have not been compared with either record.

Drugs@FDA: every ketotifen application is ophthalmic, 1999 to 2022

Regulatory record

U.S. Food and Drug Administration. Drugs@FDA application record for NDA 021066 (ZADITOR), with related ketotifen applications NDA 021996 (ALAWAY) and NDA 022388 (ACUVUE THERAVISION WITH KETOTIFEN). Dates read from the openFDA Drugs@FDA records.

Every ketotifen application in Drugs@FDA is ophthalmic. ZADITOR eye drops were first approved under NDA 021066 on 2 July 1999 (now discontinued); ALAWAY was approved under NDA 021996 on 1 December 2006 and is over the counter; a ketotifen drug-eluting contact lens (ACUVUE THERAVISION WITH KETOTIFEN, NDA 022388) was approved 25 February 2022 and is listed as discontinued. None of the 8 ketotifen fumarate applications is oral, and a search for the oral brand ZADITEN returned no match (searched 9 October 2026).

Participants / model
Not a clinical population
Treatment
Ophthalmic solutions and a drug-eluting contact lens
Follow-up
Approvals from 1999 to 2022
Study design
FDA application records
Funding
not stated in the source

These records give approval dates, over-the-counter status and discontinuation status. They show no oral ketotifen product in the US.

Read the original source
ALAWAY OTC label, version effective 1 May 2022: itchy eyes from allergens

Official label

DailyMed, U.S. National Library of Medicine. ALAWAY (ketotifen) ophthalmic solution, over-the-counter Drug Facts label, version effective 1 May 2022. Set ID e4c310b5-1dba-4ddc-bc90-b27ebc765871.

ALAWAY is an over-the-counter antihistamine eye drop containing ketotifen 0.025% (equivalent to ketotifen fumarate 0.035%) for temporary relief of itchy eyes due to ragweed, pollen, grass, animal hair, and dander, in adults and children 3 years and older.

Participants / model
Adults and children 3 years and older with allergic eye itch
Treatment
Ketotifen 0.025% ophthalmic solution
Follow-up
Label version effective 1 May 2022
Study design
Official label (OTC Drug Facts)
Funding
not stated in the source

An eye-drop label. It does not address oral use, beta-2 agonists or body composition. Directions are left out of this page.

Read the original source
EMA, June 2024: oral Zaditen authorized in eight EU and UK markets

Regulatory record

European Medicines Agency. Ketotifen oral formulations: list of nationally authorized medicinal products, PSUSA/00001813/202310, June 2024.

EMA's June 2024 list shows Zaditen capsules, tablets, syrup or oral solution, and prolonged-release tablets authorized in Belgium, Spain, France, Ireland, Italy, the Netherlands, Portugal, and Northern Ireland, all held by Alfasigma. The indication wording of these oral products was not retrieved.

Participants / model
Not a clinical population
Treatment
Oral ketotifen products
Follow-up
List dated June 2024
Study design
Official EMA record
Funding
not stated in the source

A list of national authorizations. It does not state the indications of the oral products.

Read the original source
UK Zaditen eye-drop SmPC, text revised 11 September 2025: indication, ocular exposure, oral PK

Official label

electronic Medicines Compendium (medicines.org.uk). Zaditen 0.25 mg/mL eye drops, summary of product characteristics, text revised 11 September 2025. Product 4327.

UK Zaditen 0.25 mg/mL eye drops are indicated for symptomatic treatment of seasonal allergic conjunctivitis from age 3. In 18 healthy volunteers, plasma ketotifen after 14 days of eye drops was mostly below the 20 pg/mL limit of quantitation. The same document states that after oral dosing ketotifen is eliminated in two phases, with an initial half-life of 3 to 5 hours and a terminal half-life of 21 hours, about 1% excreted unchanged in urine within 48 hours and 60 to 70% as metabolites, mainly the practically inactive ketotifen-N-glucuronide, and that oral ketotifen may potentiate CNS depressants, antihistamines, and alcohol.

Participants / model
Adults and children 3 and older with seasonal allergic conjunctivitis; 18 healthy volunteers for ocular PK
Treatment
Ketotifen 0.25 mg/mL eye drops; oral PK described for comparison
Follow-up
Text revised 11 September 2025; ocular PK after 14 days of eye drops
Study design
Official UK summary of product characteristics
Funding
not stated in the source

A UK eye-drop label, not an FDA label. The oral figures appear for comparison, and the document does not state the oral study population.

Read the original source
PubChem: ketotifen and ketotifen fumarate identity

Chemical identity record

National Library of Medicine. PubChem compound records CID 3827 (ketotifen) and CID 5282408 (ketotifen fumarate).

Ketotifen base: PubChem CID 3827, C19H19NOS, 309.4 g/mol, CAS 34580-13-7. Ketotifen fumarate, the salt in marketed products: CID 5282408, C23H23NO5S, 425.5 g/mol, CAS 34580-14-8. Strengths may be stated either way: US eye drops are labeled ketotifen 0.025% (fumarate 0.035%), and the UK eye drops contain 0.345 mg fumarate per mL, equal to 0.25 mg ketotifen.

Participants / model
Chemical identity, not a clinical population
Treatment
Base and fumarate salt
Follow-up
Not applicable
Study design
NLM chemical record
Funding
not stated in the source

Identity record only. Supplier oral products have not been compared with either record.

Read the original source

What did the asthma trials find?

A Cochrane review of 26 double-blind trials in 1,826 children found more children reduced or stopped bronchodilator use on oral ketotifen. Reported methodological quality was low, and only asthma symptom score stayed significant in the better-blinded trials.

A Cochrane review of 26 double-blind randomized trials (1,826 children aged 4 months to 18 years with asthma or wheeze) found that oral ketotifen given for 10 to 32 weeks let more children reduce or stop bronchodilator use within 12 to 16 weeks (RR 2.39, 95% CI 1.64 to 3.48, 4 trials). Several secondary outcomes favored ketotifen, but in trials with adequately described blinding only asthma symptom score remained significant.

Sedation (21% versus 12%) and weight gain (27% versus 17%) were more frequent than on placebo, and the reviewers rated the trials' reported methodological quality as low. The population was children with asthma, so these results do not describe adults using ketotifen with a beta-2 agonist.

Cochrane review: 26 trials, 1,826 children, bronchodilator use RR 2.39

Systematic review and meta-analysis

Schwarzer G et al. Cochrane Database Syst Rev. 2004;2004(1):CD001384. PMID 14973969.

In 26 double-blind randomized trials (1,826 children aged 4 months to 18 years), oral ketotifen given for 10 to 32 weeks let more children reduce or stop bronchodilator use within 12 to 16 weeks (RR 2.39, 95% CI 1.64 to 3.48, 4 trials). Several secondary outcomes favored ketotifen, but in trials with adequately described blinding only asthma symptom score remained significant. Sedation (21% versus 12%) and weight gain (27% versus 17%) were more frequent than on placebo, and the reviewers rated the trials' reported methodological quality as low.

Participants / model
Children aged 4 months to 18 years with asthma or wheeze
Treatment
Oral ketotifen (included trials gave at least 1 mg a day for at least 8 weeks)
Follow-up
10 to 32 weeks of treatment
Study design
Cochrane systematic review and meta-analysis of 26 double-blind randomized trials
Funding
not stated in the source

Children with asthma. Reported methodological quality was low, and weight gain was more frequent than on placebo.

Read the original source

Does ketotifen prevent clenbuterol tolerance, and is the supplier's description of the research right?

Partly. The 1982 to 1999 window and the absence of fat and skeletal-muscle studies hold, but the statement that no study used clenbuterol is incorrect: a 1990 asthma study combined the two. No study tested the combination for fat loss, muscle or performance.

A seller description says ketotifen is taken with a beta-2 agonist, usually clenbuterol, to prevent receptor tolerance, that it does nothing for fat loss alone, and that the beta-2 claim rests on human asthma research from 1982 to 1999, none in fat or muscle and none with clenbuterol.

A PubMed search on 9 October 2026 for ketotifen with beta-adrenoceptor and related terms returned 116 records. The human work in them runs from 1984 (in vitro modulation of adrenoceptors in human lung tissue) and 1985 (the first in vivo study) to 1999 (10 healthy men in whom ketotifen did not change responses to the beta-1 partial agonist xamoterol, which itself caused no desensitization). The 1982 record has no PubMed abstract, and the same group's 1983 paper was in rats and guinea-pig trachea. A related search limited to 2000 to 2026 returned 15 records with no human beta-receptor study. The seller's 1982 to 1999 window fits these records. The work was framed around asthma, but five of the in vivo human studies enrolled healthy volunteers, and endpoints were lymphocyte receptors, bronchial responses, and cardiovascular responses.

A PubMed search for ketotifen and clenbuterol returned 2 records: a 1990 human study of ketotifen with clenbuterol in asthma and a 1987 review of pediatric asthma treatments. ClinicalTrials.gov searches for ketotifen with clenbuterol or other beta-2 agonists returned no records. The statement that no study used clenbuterol is therefore incorrect, although no study tested the combination for fat loss, muscle, or performance. A PubMed search for ketotifen with adipose, lipolysis, obesity, fat mass, body fat, weight, skeletal muscle, muscle mass, body composition, or appetite terms returned 53 records. None tested ketotifen with a beta-2 agonist, and no human study measured adipose tissue, lipolysis, or skeletal muscle.

No source gives a ketotifen dose for use with clenbuterol, so none is given here.

PubMed search, 9 October 2026: 116 records, human work from 1984 to 1999

PubMed search record

PubMed search run on 9 October 2026: ketotifen AND (beta-adrenoceptor* OR beta-adrenergic OR beta adrenergic OR beta2 OR beta-2 OR beta-receptor* OR beta receptor* OR adrenoceptor*). 116 records returned.

The search returned 116 records. The human work in them runs from 1984 (in vitro modulation of adrenoceptors in human lung tissue, PMID 6329806) and 1985 (the first in vivo study, the lymphocyte study above) to 1999 (10 healthy men in whom ketotifen did not change responses to the beta-1 partial agonist xamoterol, which itself caused no desensitization, PMID 10073741). The 1982 record (PMID 6304954) has no PubMed abstract, and the same group's 1983 paper was in rats and guinea-pig trachea (PMID 6131826). A related search limited to 2000 to 2026 (beta-adrenoceptor, beta-adrenergic, beta2, beta-2, adrenoceptor, tachyphylaxis, or desensitization terms) returned 15 records with no human beta-receptor study. The work was framed around asthma, but five of the in vivo human studies enrolled healthy volunteers, and endpoints were lymphocyte receptors, bronchial responses, and cardiovascular responses.

Participants / model
Records returned, not a population
Treatment
Not applicable
Follow-up
Search run on 9 October 2026
Study design
Literature search
Funding
not stated in the source

A search result shows what PubMed returned on that date. It is not proof that no unindexed study exists. The 1982 record has no abstract and was reviewed by title only.

Read the original source
Searches, 9 October 2026: 2 clenbuterol records, 53 fat and muscle records, no human fat or muscle study

PubMed search record

PubMed search run on 9 October 2026: ketotifen AND clenbuterol. 2 records returned. Related searches on the same date: PubMed for ketotifen with adipose, lipolysis, obesity, fat mass, body fat, weight gain, weight loss, body weight, skeletal muscle, muscle mass, body composition, or appetite (53 records), and ClinicalTrials.gov for ketotifen with clenbuterol or other beta-2 agonists (no records).

The clenbuterol search returned 2 records: the 1990 human study of ketotifen with clenbuterol in asthma and a 1987 review of pediatric asthma treatments (PMID 3664019). The statement that no study used clenbuterol is therefore incorrect, although no study tested the combination for fat loss, muscle, or performance. ClinicalTrials.gov searches for ketotifen with clenbuterol or other beta-2 agonists returned no records. A PubMed search for ketotifen with adipose, lipolysis, obesity, fat mass, body fat, weight gain, weight loss, body weight, skeletal muscle, muscle mass, body composition, or appetite in title or abstract returned 53 records; none tested ketotifen with a beta-2 agonist, and no human study measured adipose tissue, lipolysis, or skeletal muscle. Human weight data point toward gain: weight gain was more common on ketotifen in pediatric asthma trials, and 6 HIV-infected subjects gained 2.7 kg over 84 days on oral ketotifen 4 mg a day in an open-label study (PMID 8737754). In mice, ketotifen reduced obesity on a high-cholesterol Western diet (PMID 30978390) and 45 days of intraperitoneal dosing caused weight loss (PMID 24409414); these findings are in mice only.

Participants / model
Records returned, not a population
Treatment
Not applicable
Follow-up
Searches run on 9 October 2026
Study design
Literature and registry search
Funding
not stated in the source

A search result shows what PubMed and ClinicalTrials.gov returned on that date. It is not proof that no unindexed study exists. The mouse and HIV findings come from record titles and abstracts, not separate source pages here.

Read the original source
Clenbuterol with ketotifen in asthma: lymphocyte cAMP rose, numbers not stated

Human study

Huszar E et al. Z Erkr Atmungsorgane. 1990;175(3):141-6. PMID 1964319.

In asthmatic patients treated with clenbuterol (Spiropent) for 3 months, lymphocyte beta-adrenergic function (isoproterenol-stimulated cAMP) did not differ from healthy controls. After one week of ketotifen added to clenbuterol it rose above both the clenbuterol-alone values and the healthy controls.

Participants / model
Asthmatic patients and healthy controls (numbers not stated in the truncated abstract)
Treatment
Clenbuterol for 3 months, then ketotifen with clenbuterol for 1 week (routes and doses not stated in the abstract)
Follow-up
3 months of clenbuterol, then 1 week with ketotifen added
Study design
Clinical study of lymphocyte receptor function and plasma TXB2
Funding
not stated in the source

A human study of ketotifen with clenbuterol, though in asthma and with a lymphocyte marker, not a fat, muscle, or performance outcome. The abstract is truncated and gives no sample size or doses.

Read the original source

What did the beta-2 receptor studies in healthy volunteers show?

In four small studies, ketotifen prevented or blunted loss of beta-2 responses during terbutaline or salbutamol, measured in lymphocytes, airways and cardiovascular responses. None measured fat or skeletal muscle.

In 36 healthy volunteers, terbutaline 5 mg three times daily cut lymphocyte beta-2 adrenoceptor density by about 40 to 50% and reduced cAMP responses. After terbutaline was stopped, ketotifen brought density and responsiveness back to pretreatment levels within 24 hours, against about 4 days without it, and given together with terbutaline it completely prevented the fall. This is a lymphocyte receptor marker, not an airway, fat, or muscle outcome.

In healthy volunteers, inhaled salbutamol 300 micrograms four times daily for 2 weeks made 10 of 19 tachyphylactic to its bronchodilator effect. In a double-blind crossover study in those 10, ketotifen prevented further bronchial tachyphylaxis during renewed salbutamol, while placebo did not. Whether ketotifen restores an already desensitized airway could not be determined.

In a double-blind placebo-controlled study in 10 healthy volunteers, 14 days of terbutaline 5 mg three times daily desensitized beta-2 mediated responses to isoprenaline infusion (fall in diastolic pressure, rise in plasma norepinephrine) without affecting beta-1 mediated responses. Ketotifen markedly blunted this desensitization.

In a single-blind randomized placebo-controlled crossover study in 10 healthy men (mean age 25.3), 2 weeks of oral terbutaline 5 mg three times daily reduced heart-rate and inotropic responses to terbutaline and isoprenaline infusions. Oral ketotifen significantly reduced the loss of the largely beta-2 mediated terbutaline-infusion responses but did not, or only marginally, affect the largely beta-1 mediated inotropic responses to isoprenaline. Cardiac endpoints like these are the closest this literature comes to muscle; no study measured skeletal muscle.

Lymphocyte receptors: 36 healthy volunteers, ketotifen prevented the fall

Human study

Brodde OE et al. J Clin Invest. 1985;76(3):1096-101. PMID 2995446.

Terbutaline 5 mg three times daily cut lymphocyte beta-2 adrenoceptor density by about 40 to 50% and reduced cAMP responses. After terbutaline was stopped, ketotifen brought density and responsiveness back to pretreatment levels within 24 hours, against about 4 days without it, and given together with terbutaline it completely prevented the fall.

Participants / model
36 healthy volunteers
Treatment
Terbutaline with or without ketotifen 2 mg then 1 mg twice daily
Follow-up
not stated in the source
Study design
Clinical study of lymphocyte receptor density and cAMP response
Funding
not stated in the source

This is a lymphocyte receptor marker, not an airway, fat, or muscle outcome.

Read the original source
Salbutamol tachyphylaxis: 19 healthy volunteers, 10 in the crossover

Randomized controlled trial

Pauwels R et al. J Allergy Clin Immunol. 1988;81(4):674-80. PMID 3281997.

Inhaled salbutamol 300 micrograms four times daily for 2 weeks made 10 of 19 volunteers tachyphylactic to its bronchodilator effect. In a double-blind crossover study in those 10, ketotifen prevented further bronchial tachyphylaxis during renewed salbutamol, while placebo did not. Whether ketotifen restores an already desensitized airway could not be determined.

Participants / model
19 healthy volunteers, 10 in the crossover phase
Treatment
Inhaled salbutamol with ketotifen or placebo
Follow-up
2 weeks of salbutamol, then a crossover with ketotifen for 1 week and then 3 weeks
Study design
Double-blind crossover trial; bronchial dose-response to salbutamol
Funding
not stated in the source

An airway outcome in healthy volunteers. It does not address fat, muscle or clenbuterol.

Read the original source
Isoprenaline responses: 10 healthy volunteers, ketotifen blunted desensitization

Randomized controlled trial

Brodde OE et al. J Cardiovasc Pharmacol. 1992;20(3):434-9. PMID 1279289.

14 days of terbutaline 5 mg three times daily desensitized beta-2 mediated responses to isoprenaline infusion (fall in diastolic pressure, rise in plasma norepinephrine) without affecting beta-1 mediated responses. Ketotifen markedly blunted this desensitization.

Participants / model
10 healthy volunteers
Treatment
Terbutaline with ketotifen 1 mg twice daily or placebo
Follow-up
14 days
Study design
Double-blind placebo-controlled study
Funding
not stated in the source

Cardiovascular and plasma norepinephrine endpoints in healthy volunteers.

Read the original source
Cardiac responses: 10 healthy men, ketotifen reduced loss of beta-2 responses

Randomized controlled trial

Poller U et al. Cardiovasc Res. 1998;40(1):211-22. PMID 9876334.

2 weeks of oral terbutaline 5 mg three times daily reduced heart-rate and inotropic responses to terbutaline and isoprenaline infusions. Oral ketotifen significantly reduced the loss of the largely beta-2 mediated terbutaline-infusion responses but did not, or only marginally, affect the largely beta-1 mediated inotropic responses to isoprenaline.

Participants / model
10 healthy men (mean age 25.3)
Treatment
Oral terbutaline with oral ketotifen or placebo
Follow-up
2 weeks of terbutaline; ketotifen for 3 weeks
Study design
Single-blind randomized placebo-controlled crossover study; systolic time intervals
Funding
not stated in the source

Cardiac endpoints like these are the closest this literature comes to muscle. No study measured skeletal muscle.

Read the original source

What do the asthma studies show about beta-adrenergic function and clenbuterol?

One asthma study found no effect of ketotifen on the beta-adrenergic system, and a 1990 asthma study found lymphocyte beta-adrenergic function rose when ketotifen was added to clenbuterol. The 1990 abstract gives no sample size or doses.

In a double-blind study in asthmatic patients, ketotifen for one month did not change the spirometric, plasma potassium, or serum glucose responses to nebulized salbutamol, or the skin wheal response to local salbutamol, compared with placebo. The authors concluded that ketotifen at the doses studied had no demonstrable effect on the beta-adrenergic system in asthma.

In asthmatic patients treated with clenbuterol (Spiropent) for 3 months, lymphocyte beta-adrenergic function (isoproterenol-stimulated cAMP) did not differ from healthy controls. After one week of ketotifen added to clenbuterol it rose above both the clenbuterol-alone values and the healthy controls. This is a human study of ketotifen with clenbuterol, though in asthma and with a lymphocyte marker, not a fat, muscle, or performance outcome. The abstract is truncated and gives no sample size, routes or doses.

Asthma study: no effect of ketotifen on salbutamol responses

Randomized controlled trial

Gove RI et al. Eur J Clin Pharmacol. 1988;34(6):585-9. PMID 2844549.

Ketotifen for one month did not change the spirometric, plasma potassium, or serum glucose responses to nebulized salbutamol, or the skin wheal response to local salbutamol, compared with placebo. The authors concluded that ketotifen at the doses studied had no demonstrable effect on the beta-adrenergic system in asthma.

Participants / model
Patients with asthma (number not stated in the abstract)
Treatment
Ketotifen 1 mg twice daily for one month; nebulized and intradermal salbutamol
Follow-up
One month
Study design
Double-blind controlled study
Funding
not stated in the source

A null result in asthma patients, which differs from the healthy-volunteer findings.

Read the original source
Clenbuterol with ketotifen in asthma: lymphocyte cAMP rose, numbers not stated

Human study

Huszar E et al. Z Erkr Atmungsorgane. 1990;175(3):141-6. PMID 1964319.

In asthmatic patients treated with clenbuterol (Spiropent) for 3 months, lymphocyte beta-adrenergic function (isoproterenol-stimulated cAMP) did not differ from healthy controls. After one week of ketotifen added to clenbuterol it rose above both the clenbuterol-alone values and the healthy controls.

Participants / model
Asthmatic patients and healthy controls (numbers not stated in the truncated abstract)
Treatment
Clenbuterol for 3 months, then ketotifen with clenbuterol for 1 week (routes and doses not stated in the abstract)
Follow-up
3 months of clenbuterol, then 1 week with ketotifen added
Study design
Clinical study of lymphocyte receptor function and plasma TXB2
Funding
not stated in the source

A human study of ketotifen with clenbuterol, though in asthma and with a lymphocyte marker, not a fat, muscle, or performance outcome. The abstract is truncated and gives no sample size or doses.

Read the original source

Does ketotifen change fat loss, muscle or body weight?

No human study measured adipose tissue, lipolysis or skeletal muscle. Human weight data point toward gain, apart from a 2026 fatty-liver pilot that reported smaller hip and waist-stature measures than vitamin E without any change in weight or BMI.

Human weight data point toward gain. Weight gain was more common on ketotifen than placebo in pediatric asthma trials (27% versus 17%), and 6 HIV-infected subjects gained 2.7 kg over 84 days on oral ketotifen 4 mg a day in an open-label study.

In a randomized pilot study, 60 adults with non-alcoholic fatty liver disease received ketotifen or vitamin E for 6 months. Ketotifen reduced hepatic steatosis and fibrosis scores, HOMA-IR, fasting glucose and insulin, AST, TNF-alpha, and MMP-9, and improved hip circumference and waist-stature ratio, but body weight, BMI, lipids, and HbA1c did not differ between groups. The comparator was vitamin E, not placebo, and NCT05616442 is registered as a completed phase 4 trial of 60 participants with no posted results.

In mice, ketotifen reduced obesity on a high-cholesterol Western diet, and 45 days of intraperitoneal dosing caused weight loss. These findings are in mice only. A statement that ketotifen does nothing for fat loss alone fits the human weight data, apart from the one 2026 pilot.

Cochrane review: 26 trials, 1,826 children, bronchodilator use RR 2.39

Systematic review and meta-analysis

Schwarzer G et al. Cochrane Database Syst Rev. 2004;2004(1):CD001384. PMID 14973969.

In 26 double-blind randomized trials (1,826 children aged 4 months to 18 years), oral ketotifen given for 10 to 32 weeks let more children reduce or stop bronchodilator use within 12 to 16 weeks (RR 2.39, 95% CI 1.64 to 3.48, 4 trials). Several secondary outcomes favored ketotifen, but in trials with adequately described blinding only asthma symptom score remained significant. Sedation (21% versus 12%) and weight gain (27% versus 17%) were more frequent than on placebo, and the reviewers rated the trials' reported methodological quality as low.

Participants / model
Children aged 4 months to 18 years with asthma or wheeze
Treatment
Oral ketotifen (included trials gave at least 1 mg a day for at least 8 weeks)
Follow-up
10 to 32 weeks of treatment
Study design
Cochrane systematic review and meta-analysis of 26 double-blind randomized trials
Funding
not stated in the source

Children with asthma. Reported methodological quality was low, and weight gain was more frequent than on placebo.

Read the original source
Searches, 9 October 2026: 2 clenbuterol records, 53 fat and muscle records, no human fat or muscle study

PubMed search record

PubMed search run on 9 October 2026: ketotifen AND clenbuterol. 2 records returned. Related searches on the same date: PubMed for ketotifen with adipose, lipolysis, obesity, fat mass, body fat, weight gain, weight loss, body weight, skeletal muscle, muscle mass, body composition, or appetite (53 records), and ClinicalTrials.gov for ketotifen with clenbuterol or other beta-2 agonists (no records).

The clenbuterol search returned 2 records: the 1990 human study of ketotifen with clenbuterol in asthma and a 1987 review of pediatric asthma treatments (PMID 3664019). The statement that no study used clenbuterol is therefore incorrect, although no study tested the combination for fat loss, muscle, or performance. ClinicalTrials.gov searches for ketotifen with clenbuterol or other beta-2 agonists returned no records. A PubMed search for ketotifen with adipose, lipolysis, obesity, fat mass, body fat, weight gain, weight loss, body weight, skeletal muscle, muscle mass, body composition, or appetite in title or abstract returned 53 records; none tested ketotifen with a beta-2 agonist, and no human study measured adipose tissue, lipolysis, or skeletal muscle. Human weight data point toward gain: weight gain was more common on ketotifen in pediatric asthma trials, and 6 HIV-infected subjects gained 2.7 kg over 84 days on oral ketotifen 4 mg a day in an open-label study (PMID 8737754). In mice, ketotifen reduced obesity on a high-cholesterol Western diet (PMID 30978390) and 45 days of intraperitoneal dosing caused weight loss (PMID 24409414); these findings are in mice only.

Participants / model
Records returned, not a population
Treatment
Not applicable
Follow-up
Searches run on 9 October 2026
Study design
Literature and registry search
Funding
not stated in the source

A search result shows what PubMed and ClinicalTrials.gov returned on that date. It is not proof that no unindexed study exists. The mouse and HIV findings come from record titles and abstracts, not separate source pages here.

Read the original source
Fatty liver pilot: 60 adults, 6 months, versus vitamin E, no change in weight or BMI

Randomized controlled trial

Aldossary KM et al. Drug Des Devel Ther. 2026;20:593561. PMID 42039690.

Ketotifen reduced hepatic steatosis and fibrosis scores, HOMA-IR, fasting glucose and insulin, AST, TNF-alpha, and MMP-9, and improved hip circumference and waist-stature ratio, but body weight, BMI, lipids, and HbA1c did not differ between groups. Drowsiness was the most common adverse event.

Participants / model
60 adults with non-alcoholic fatty liver disease
Treatment
Ketotifen versus vitamin E for 6 months (route and dose not stated in the abstract)
Follow-up
6 months
Study design
Randomized pilot trial
Funding
not stated in the source

The comparator was vitamin E, not placebo. NCT05616442 is registered as a completed phase 4 trial of 60 participants with no posted results.

Read the original source

How does ketotifen work, and what does the body do with it?

ALAWAY is labeled as an antihistamine eye drop, and the beta-2 anti-desensitization effect appears in small volunteer studies. After oral dosing, the UK label document gives a terminal half-life of 21 hours.

ALAWAY is labeled as an antihistamine eye drop. The beta-2 anti-desensitization effect shows up in small human studies of lymphocytes, airways and cardiovascular responses in healthy volunteers, while one asthma study found no effect on the beta-adrenergic system. The sources reviewed give no further receptor mechanism.

The UK Zaditen eye-drop document states that after oral dosing ketotifen is eliminated in two phases, with an initial half-life of 3 to 5 hours and a terminal half-life of 21 hours, about 1% excreted unchanged in urine within 48 hours and 60 to 70% as metabolites, mainly the practically inactive ketotifen-N-glucuronide. In 18 healthy volunteers, plasma ketotifen after 14 days of eye drops was mostly below the 20 pg/mL limit of quantitation.

ALAWAY OTC label, version effective 1 May 2022: itchy eyes from allergens

Official label

DailyMed, U.S. National Library of Medicine. ALAWAY (ketotifen) ophthalmic solution, over-the-counter Drug Facts label, version effective 1 May 2022. Set ID e4c310b5-1dba-4ddc-bc90-b27ebc765871.

ALAWAY is an over-the-counter antihistamine eye drop containing ketotifen 0.025% (equivalent to ketotifen fumarate 0.035%) for temporary relief of itchy eyes due to ragweed, pollen, grass, animal hair, and dander, in adults and children 3 years and older.

Participants / model
Adults and children 3 years and older with allergic eye itch
Treatment
Ketotifen 0.025% ophthalmic solution
Follow-up
Label version effective 1 May 2022
Study design
Official label (OTC Drug Facts)
Funding
not stated in the source

An eye-drop label. It does not address oral use, beta-2 agonists or body composition. Directions are left out of this page.

Read the original source
UK Zaditen eye-drop SmPC, text revised 11 September 2025: indication, ocular exposure, oral PK

Official label

electronic Medicines Compendium (medicines.org.uk). Zaditen 0.25 mg/mL eye drops, summary of product characteristics, text revised 11 September 2025. Product 4327.

UK Zaditen 0.25 mg/mL eye drops are indicated for symptomatic treatment of seasonal allergic conjunctivitis from age 3. In 18 healthy volunteers, plasma ketotifen after 14 days of eye drops was mostly below the 20 pg/mL limit of quantitation. The same document states that after oral dosing ketotifen is eliminated in two phases, with an initial half-life of 3 to 5 hours and a terminal half-life of 21 hours, about 1% excreted unchanged in urine within 48 hours and 60 to 70% as metabolites, mainly the practically inactive ketotifen-N-glucuronide, and that oral ketotifen may potentiate CNS depressants, antihistamines, and alcohol.

Participants / model
Adults and children 3 and older with seasonal allergic conjunctivitis; 18 healthy volunteers for ocular PK
Treatment
Ketotifen 0.25 mg/mL eye drops; oral PK described for comparison
Follow-up
Text revised 11 September 2025; ocular PK after 14 days of eye drops
Study design
Official UK summary of product characteristics
Funding
not stated in the source

A UK eye-drop label, not an FDA label. The oral figures appear for comparison, and the document does not state the oral study population.

Read the original source
Lymphocyte receptors: 36 healthy volunteers, ketotifen prevented the fall

Human study

Brodde OE et al. J Clin Invest. 1985;76(3):1096-101. PMID 2995446.

Terbutaline 5 mg three times daily cut lymphocyte beta-2 adrenoceptor density by about 40 to 50% and reduced cAMP responses. After terbutaline was stopped, ketotifen brought density and responsiveness back to pretreatment levels within 24 hours, against about 4 days without it, and given together with terbutaline it completely prevented the fall.

Participants / model
36 healthy volunteers
Treatment
Terbutaline with or without ketotifen 2 mg then 1 mg twice daily
Follow-up
not stated in the source
Study design
Clinical study of lymphocyte receptor density and cAMP response
Funding
not stated in the source

This is a lymphocyte receptor marker, not an airway, fat, or muscle outcome.

Read the original source
Asthma study: no effect of ketotifen on salbutamol responses

Randomized controlled trial

Gove RI et al. Eur J Clin Pharmacol. 1988;34(6):585-9. PMID 2844549.

Ketotifen for one month did not change the spirometric, plasma potassium, or serum glucose responses to nebulized salbutamol, or the skin wheal response to local salbutamol, compared with placebo. The authors concluded that ketotifen at the doses studied had no demonstrable effect on the beta-adrenergic system in asthma.

Participants / model
Patients with asthma (number not stated in the abstract)
Treatment
Ketotifen 1 mg twice daily for one month; nebulized and intradermal salbutamol
Follow-up
One month
Study design
Double-blind controlled study
Funding
not stated in the source

A null result in asthma patients, which differs from the healthy-volunteer findings.

Read the original source

What risks do the labels and studies report?

The main adverse effects reported were sedation and weight gain, both more frequent than on placebo in pediatric asthma trials, and the UK label document states oral ketotifen may potentiate CNS depressants, antihistamines and alcohol. No study tested the combination with clenbuterol for body composition, so its risks are unmeasured.

In the Cochrane review of pediatric asthma trials, sedation (21% versus 12%) and weight gain (27% versus 17%) were more frequent than on placebo. Drowsiness was the most common adverse event in the 2026 fatty-liver pilot.

The UK Zaditen eye-drop document states that oral ketotifen may potentiate CNS depressants, antihistamines, and alcohol.

No study tested ketotifen with clenbuterol or another beta-2 agonist for fat loss, muscle, or performance, so benefit and harm for that use are unmeasured. The 1990 clenbuterol study and the volunteer studies used lymphocyte, airway and cardiovascular markers, and the 1990 abstract gives no sample size or doses.

Cochrane review: 26 trials, 1,826 children, bronchodilator use RR 2.39

Systematic review and meta-analysis

Schwarzer G et al. Cochrane Database Syst Rev. 2004;2004(1):CD001384. PMID 14973969.

In 26 double-blind randomized trials (1,826 children aged 4 months to 18 years), oral ketotifen given for 10 to 32 weeks let more children reduce or stop bronchodilator use within 12 to 16 weeks (RR 2.39, 95% CI 1.64 to 3.48, 4 trials). Several secondary outcomes favored ketotifen, but in trials with adequately described blinding only asthma symptom score remained significant. Sedation (21% versus 12%) and weight gain (27% versus 17%) were more frequent than on placebo, and the reviewers rated the trials' reported methodological quality as low.

Participants / model
Children aged 4 months to 18 years with asthma or wheeze
Treatment
Oral ketotifen (included trials gave at least 1 mg a day for at least 8 weeks)
Follow-up
10 to 32 weeks of treatment
Study design
Cochrane systematic review and meta-analysis of 26 double-blind randomized trials
Funding
not stated in the source

Children with asthma. Reported methodological quality was low, and weight gain was more frequent than on placebo.

Read the original source
UK Zaditen eye-drop SmPC, text revised 11 September 2025: indication, ocular exposure, oral PK

Official label

electronic Medicines Compendium (medicines.org.uk). Zaditen 0.25 mg/mL eye drops, summary of product characteristics, text revised 11 September 2025. Product 4327.

UK Zaditen 0.25 mg/mL eye drops are indicated for symptomatic treatment of seasonal allergic conjunctivitis from age 3. In 18 healthy volunteers, plasma ketotifen after 14 days of eye drops was mostly below the 20 pg/mL limit of quantitation. The same document states that after oral dosing ketotifen is eliminated in two phases, with an initial half-life of 3 to 5 hours and a terminal half-life of 21 hours, about 1% excreted unchanged in urine within 48 hours and 60 to 70% as metabolites, mainly the practically inactive ketotifen-N-glucuronide, and that oral ketotifen may potentiate CNS depressants, antihistamines, and alcohol.

Participants / model
Adults and children 3 and older with seasonal allergic conjunctivitis; 18 healthy volunteers for ocular PK
Treatment
Ketotifen 0.25 mg/mL eye drops; oral PK described for comparison
Follow-up
Text revised 11 September 2025; ocular PK after 14 days of eye drops
Study design
Official UK summary of product characteristics
Funding
not stated in the source

A UK eye-drop label, not an FDA label. The oral figures appear for comparison, and the document does not state the oral study population.

Read the original source
Fatty liver pilot: 60 adults, 6 months, versus vitamin E, no change in weight or BMI

Randomized controlled trial

Aldossary KM et al. Drug Des Devel Ther. 2026;20:593561. PMID 42039690.

Ketotifen reduced hepatic steatosis and fibrosis scores, HOMA-IR, fasting glucose and insulin, AST, TNF-alpha, and MMP-9, and improved hip circumference and waist-stature ratio, but body weight, BMI, lipids, and HbA1c did not differ between groups. Drowsiness was the most common adverse event.

Participants / model
60 adults with non-alcoholic fatty liver disease
Treatment
Ketotifen versus vitamin E for 6 months (route and dose not stated in the abstract)
Follow-up
6 months
Study design
Randomized pilot trial
Funding
not stated in the source

The comparator was vitamin E, not placebo. NCT05616442 is registered as a completed phase 4 trial of 60 participants with no posted results.

Read the original source

Why does ketotifen sit in A tier?

An approved antiallergic, FDA-approved as eye drops and authorized orally in several EU countries, promoted for an off-label use supports the A. The beta-2 effect rests on small asthma and volunteer studies, and nothing connects it to fat loss, muscle or clenbuterol use.

Ketotifen is approved as an antiallergic, ophthalmic in the US and oral in several EU countries. The clenbuterol-tolerance use is off-label and rests on old asthma and volunteer receptor studies. A Cochrane review supports pediatric asthma control from trials of low reported quality.

The beta-2 anti-desensitization effect shows up in small human studies of lymphocytes, airways, and cardiovascular responses, but one asthma study found no effect, and nothing connects it to fat loss, muscle, or clenbuterol use for body composition. Sedation and weight gain are documented.

The supplier description gets its own verdict. The 1982 to 1999 window and the absence of fat and skeletal-muscle studies hold for the records found. The claim that no study used clenbuterol is wrong, because a 1990 asthma study combined the two, and several of the human studies were in healthy volunteers rather than asthma patients. The statement that it does nothing for fat loss alone fits the human weight data, apart from one 2026 pilot.

Drugs@FDA: every ketotifen application is ophthalmic, 1999 to 2022

Regulatory record

U.S. Food and Drug Administration. Drugs@FDA application record for NDA 021066 (ZADITOR), with related ketotifen applications NDA 021996 (ALAWAY) and NDA 022388 (ACUVUE THERAVISION WITH KETOTIFEN). Dates read from the openFDA Drugs@FDA records.

Every ketotifen application in Drugs@FDA is ophthalmic. ZADITOR eye drops were first approved under NDA 021066 on 2 July 1999 (now discontinued); ALAWAY was approved under NDA 021996 on 1 December 2006 and is over the counter; a ketotifen drug-eluting contact lens (ACUVUE THERAVISION WITH KETOTIFEN, NDA 022388) was approved 25 February 2022 and is listed as discontinued. None of the 8 ketotifen fumarate applications is oral, and a search for the oral brand ZADITEN returned no match (searched 9 October 2026).

Participants / model
Not a clinical population
Treatment
Ophthalmic solutions and a drug-eluting contact lens
Follow-up
Approvals from 1999 to 2022
Study design
FDA application records
Funding
not stated in the source

These records give approval dates, over-the-counter status and discontinuation status. They show no oral ketotifen product in the US.

Read the original source
EMA, June 2024: oral Zaditen authorized in eight EU and UK markets

Regulatory record

European Medicines Agency. Ketotifen oral formulations: list of nationally authorized medicinal products, PSUSA/00001813/202310, June 2024.

EMA's June 2024 list shows Zaditen capsules, tablets, syrup or oral solution, and prolonged-release tablets authorized in Belgium, Spain, France, Ireland, Italy, the Netherlands, Portugal, and Northern Ireland, all held by Alfasigma. The indication wording of these oral products was not retrieved.

Participants / model
Not a clinical population
Treatment
Oral ketotifen products
Follow-up
List dated June 2024
Study design
Official EMA record
Funding
not stated in the source

A list of national authorizations. It does not state the indications of the oral products.

Read the original source
Cochrane review: 26 trials, 1,826 children, bronchodilator use RR 2.39

Systematic review and meta-analysis

Schwarzer G et al. Cochrane Database Syst Rev. 2004;2004(1):CD001384. PMID 14973969.

In 26 double-blind randomized trials (1,826 children aged 4 months to 18 years), oral ketotifen given for 10 to 32 weeks let more children reduce or stop bronchodilator use within 12 to 16 weeks (RR 2.39, 95% CI 1.64 to 3.48, 4 trials). Several secondary outcomes favored ketotifen, but in trials with adequately described blinding only asthma symptom score remained significant. Sedation (21% versus 12%) and weight gain (27% versus 17%) were more frequent than on placebo, and the reviewers rated the trials' reported methodological quality as low.

Participants / model
Children aged 4 months to 18 years with asthma or wheeze
Treatment
Oral ketotifen (included trials gave at least 1 mg a day for at least 8 weeks)
Follow-up
10 to 32 weeks of treatment
Study design
Cochrane systematic review and meta-analysis of 26 double-blind randomized trials
Funding
not stated in the source

Children with asthma. Reported methodological quality was low, and weight gain was more frequent than on placebo.

Read the original source
PubMed search, 9 October 2026: 116 records, human work from 1984 to 1999

PubMed search record

PubMed search run on 9 October 2026: ketotifen AND (beta-adrenoceptor* OR beta-adrenergic OR beta adrenergic OR beta2 OR beta-2 OR beta-receptor* OR beta receptor* OR adrenoceptor*). 116 records returned.

The search returned 116 records. The human work in them runs from 1984 (in vitro modulation of adrenoceptors in human lung tissue, PMID 6329806) and 1985 (the first in vivo study, the lymphocyte study above) to 1999 (10 healthy men in whom ketotifen did not change responses to the beta-1 partial agonist xamoterol, which itself caused no desensitization, PMID 10073741). The 1982 record (PMID 6304954) has no PubMed abstract, and the same group's 1983 paper was in rats and guinea-pig trachea (PMID 6131826). A related search limited to 2000 to 2026 (beta-adrenoceptor, beta-adrenergic, beta2, beta-2, adrenoceptor, tachyphylaxis, or desensitization terms) returned 15 records with no human beta-receptor study. The work was framed around asthma, but five of the in vivo human studies enrolled healthy volunteers, and endpoints were lymphocyte receptors, bronchial responses, and cardiovascular responses.

Participants / model
Records returned, not a population
Treatment
Not applicable
Follow-up
Search run on 9 October 2026
Study design
Literature search
Funding
not stated in the source

A search result shows what PubMed returned on that date. It is not proof that no unindexed study exists. The 1982 record has no abstract and was reviewed by title only.

Read the original source
Searches, 9 October 2026: 2 clenbuterol records, 53 fat and muscle records, no human fat or muscle study

PubMed search record

PubMed search run on 9 October 2026: ketotifen AND clenbuterol. 2 records returned. Related searches on the same date: PubMed for ketotifen with adipose, lipolysis, obesity, fat mass, body fat, weight gain, weight loss, body weight, skeletal muscle, muscle mass, body composition, or appetite (53 records), and ClinicalTrials.gov for ketotifen with clenbuterol or other beta-2 agonists (no records).

The clenbuterol search returned 2 records: the 1990 human study of ketotifen with clenbuterol in asthma and a 1987 review of pediatric asthma treatments (PMID 3664019). The statement that no study used clenbuterol is therefore incorrect, although no study tested the combination for fat loss, muscle, or performance. ClinicalTrials.gov searches for ketotifen with clenbuterol or other beta-2 agonists returned no records. A PubMed search for ketotifen with adipose, lipolysis, obesity, fat mass, body fat, weight gain, weight loss, body weight, skeletal muscle, muscle mass, body composition, or appetite in title or abstract returned 53 records; none tested ketotifen with a beta-2 agonist, and no human study measured adipose tissue, lipolysis, or skeletal muscle. Human weight data point toward gain: weight gain was more common on ketotifen in pediatric asthma trials, and 6 HIV-infected subjects gained 2.7 kg over 84 days on oral ketotifen 4 mg a day in an open-label study (PMID 8737754). In mice, ketotifen reduced obesity on a high-cholesterol Western diet (PMID 30978390) and 45 days of intraperitoneal dosing caused weight loss (PMID 24409414); these findings are in mice only.

Participants / model
Records returned, not a population
Treatment
Not applicable
Follow-up
Searches run on 9 October 2026
Study design
Literature and registry search
Funding
not stated in the source

A search result shows what PubMed and ClinicalTrials.gov returned on that date. It is not proof that no unindexed study exists. The mouse and HIV findings come from record titles and abstracts, not separate source pages here.

Read the original source
Clenbuterol with ketotifen in asthma: lymphocyte cAMP rose, numbers not stated

Human study

Huszar E et al. Z Erkr Atmungsorgane. 1990;175(3):141-6. PMID 1964319.

In asthmatic patients treated with clenbuterol (Spiropent) for 3 months, lymphocyte beta-adrenergic function (isoproterenol-stimulated cAMP) did not differ from healthy controls. After one week of ketotifen added to clenbuterol it rose above both the clenbuterol-alone values and the healthy controls.

Participants / model
Asthmatic patients and healthy controls (numbers not stated in the truncated abstract)
Treatment
Clenbuterol for 3 months, then ketotifen with clenbuterol for 1 week (routes and doses not stated in the abstract)
Follow-up
3 months of clenbuterol, then 1 week with ketotifen added
Study design
Clinical study of lymphocyte receptor function and plasma TXB2
Funding
not stated in the source

A human study of ketotifen with clenbuterol, though in asthma and with a lymphocyte marker, not a fat, muscle, or performance outcome. The abstract is truncated and gives no sample size or doses.

Read the original source

Studies and sources

Drugs@FDA: every ketotifen application is ophthalmic, 1999 to 2022

Regulatory record

U.S. Food and Drug Administration. Drugs@FDA application record for NDA 021066 (ZADITOR), with related ketotifen applications NDA 021996 (ALAWAY) and NDA 022388 (ACUVUE THERAVISION WITH KETOTIFEN). Dates read from the openFDA Drugs@FDA records.

Every ketotifen application in Drugs@FDA is ophthalmic. ZADITOR eye drops were first approved under NDA 021066 on 2 July 1999 (now discontinued); ALAWAY was approved under NDA 021996 on 1 December 2006 and is over the counter; a ketotifen drug-eluting contact lens (ACUVUE THERAVISION WITH KETOTIFEN, NDA 022388) was approved 25 February 2022 and is listed as discontinued. None of the 8 ketotifen fumarate applications is oral, and a search for the oral brand ZADITEN returned no match (searched 9 October 2026).

Participants / model
Not a clinical population
Treatment
Ophthalmic solutions and a drug-eluting contact lens
Follow-up
Approvals from 1999 to 2022
Study design
FDA application records
Funding
not stated in the source

These records give approval dates, over-the-counter status and discontinuation status. They show no oral ketotifen product in the US.

Read the original source
ALAWAY OTC label, version effective 1 May 2022: itchy eyes from allergens

Official label

DailyMed, U.S. National Library of Medicine. ALAWAY (ketotifen) ophthalmic solution, over-the-counter Drug Facts label, version effective 1 May 2022. Set ID e4c310b5-1dba-4ddc-bc90-b27ebc765871.

ALAWAY is an over-the-counter antihistamine eye drop containing ketotifen 0.025% (equivalent to ketotifen fumarate 0.035%) for temporary relief of itchy eyes due to ragweed, pollen, grass, animal hair, and dander, in adults and children 3 years and older.

Participants / model
Adults and children 3 years and older with allergic eye itch
Treatment
Ketotifen 0.025% ophthalmic solution
Follow-up
Label version effective 1 May 2022
Study design
Official label (OTC Drug Facts)
Funding
not stated in the source

An eye-drop label. It does not address oral use, beta-2 agonists or body composition. Directions are left out of this page.

Read the original source
UK Zaditen eye-drop SmPC, text revised 11 September 2025: indication, ocular exposure, oral PK

Official label

electronic Medicines Compendium (medicines.org.uk). Zaditen 0.25 mg/mL eye drops, summary of product characteristics, text revised 11 September 2025. Product 4327.

UK Zaditen 0.25 mg/mL eye drops are indicated for symptomatic treatment of seasonal allergic conjunctivitis from age 3. In 18 healthy volunteers, plasma ketotifen after 14 days of eye drops was mostly below the 20 pg/mL limit of quantitation. The same document states that after oral dosing ketotifen is eliminated in two phases, with an initial half-life of 3 to 5 hours and a terminal half-life of 21 hours, about 1% excreted unchanged in urine within 48 hours and 60 to 70% as metabolites, mainly the practically inactive ketotifen-N-glucuronide, and that oral ketotifen may potentiate CNS depressants, antihistamines, and alcohol.

Participants / model
Adults and children 3 and older with seasonal allergic conjunctivitis; 18 healthy volunteers for ocular PK
Treatment
Ketotifen 0.25 mg/mL eye drops; oral PK described for comparison
Follow-up
Text revised 11 September 2025; ocular PK after 14 days of eye drops
Study design
Official UK summary of product characteristics
Funding
not stated in the source

A UK eye-drop label, not an FDA label. The oral figures appear for comparison, and the document does not state the oral study population.

Read the original source
EMA, June 2024: oral Zaditen authorized in eight EU and UK markets

Regulatory record

European Medicines Agency. Ketotifen oral formulations: list of nationally authorized medicinal products, PSUSA/00001813/202310, June 2024.

EMA's June 2024 list shows Zaditen capsules, tablets, syrup or oral solution, and prolonged-release tablets authorized in Belgium, Spain, France, Ireland, Italy, the Netherlands, Portugal, and Northern Ireland, all held by Alfasigma. The indication wording of these oral products was not retrieved.

Participants / model
Not a clinical population
Treatment
Oral ketotifen products
Follow-up
List dated June 2024
Study design
Official EMA record
Funding
not stated in the source

A list of national authorizations. It does not state the indications of the oral products.

Read the original source
Cochrane review: 26 trials, 1,826 children, bronchodilator use RR 2.39

Systematic review and meta-analysis

Schwarzer G et al. Cochrane Database Syst Rev. 2004;2004(1):CD001384. PMID 14973969.

In 26 double-blind randomized trials (1,826 children aged 4 months to 18 years), oral ketotifen given for 10 to 32 weeks let more children reduce or stop bronchodilator use within 12 to 16 weeks (RR 2.39, 95% CI 1.64 to 3.48, 4 trials). Several secondary outcomes favored ketotifen, but in trials with adequately described blinding only asthma symptom score remained significant. Sedation (21% versus 12%) and weight gain (27% versus 17%) were more frequent than on placebo, and the reviewers rated the trials' reported methodological quality as low.

Participants / model
Children aged 4 months to 18 years with asthma or wheeze
Treatment
Oral ketotifen (included trials gave at least 1 mg a day for at least 8 weeks)
Follow-up
10 to 32 weeks of treatment
Study design
Cochrane systematic review and meta-analysis of 26 double-blind randomized trials
Funding
not stated in the source

Children with asthma. Reported methodological quality was low, and weight gain was more frequent than on placebo.

Read the original source
Lymphocyte receptors: 36 healthy volunteers, ketotifen prevented the fall

Human study

Brodde OE et al. J Clin Invest. 1985;76(3):1096-101. PMID 2995446.

Terbutaline 5 mg three times daily cut lymphocyte beta-2 adrenoceptor density by about 40 to 50% and reduced cAMP responses. After terbutaline was stopped, ketotifen brought density and responsiveness back to pretreatment levels within 24 hours, against about 4 days without it, and given together with terbutaline it completely prevented the fall.

Participants / model
36 healthy volunteers
Treatment
Terbutaline with or without ketotifen 2 mg then 1 mg twice daily
Follow-up
not stated in the source
Study design
Clinical study of lymphocyte receptor density and cAMP response
Funding
not stated in the source

This is a lymphocyte receptor marker, not an airway, fat, or muscle outcome.

Read the original source
Salbutamol tachyphylaxis: 19 healthy volunteers, 10 in the crossover

Randomized controlled trial

Pauwels R et al. J Allergy Clin Immunol. 1988;81(4):674-80. PMID 3281997.

Inhaled salbutamol 300 micrograms four times daily for 2 weeks made 10 of 19 volunteers tachyphylactic to its bronchodilator effect. In a double-blind crossover study in those 10, ketotifen prevented further bronchial tachyphylaxis during renewed salbutamol, while placebo did not. Whether ketotifen restores an already desensitized airway could not be determined.

Participants / model
19 healthy volunteers, 10 in the crossover phase
Treatment
Inhaled salbutamol with ketotifen or placebo
Follow-up
2 weeks of salbutamol, then a crossover with ketotifen for 1 week and then 3 weeks
Study design
Double-blind crossover trial; bronchial dose-response to salbutamol
Funding
not stated in the source

An airway outcome in healthy volunteers. It does not address fat, muscle or clenbuterol.

Read the original source
Isoprenaline responses: 10 healthy volunteers, ketotifen blunted desensitization

Randomized controlled trial

Brodde OE et al. J Cardiovasc Pharmacol. 1992;20(3):434-9. PMID 1279289.

14 days of terbutaline 5 mg three times daily desensitized beta-2 mediated responses to isoprenaline infusion (fall in diastolic pressure, rise in plasma norepinephrine) without affecting beta-1 mediated responses. Ketotifen markedly blunted this desensitization.

Participants / model
10 healthy volunteers
Treatment
Terbutaline with ketotifen 1 mg twice daily or placebo
Follow-up
14 days
Study design
Double-blind placebo-controlled study
Funding
not stated in the source

Cardiovascular and plasma norepinephrine endpoints in healthy volunteers.

Read the original source
Cardiac responses: 10 healthy men, ketotifen reduced loss of beta-2 responses

Randomized controlled trial

Poller U et al. Cardiovasc Res. 1998;40(1):211-22. PMID 9876334.

2 weeks of oral terbutaline 5 mg three times daily reduced heart-rate and inotropic responses to terbutaline and isoprenaline infusions. Oral ketotifen significantly reduced the loss of the largely beta-2 mediated terbutaline-infusion responses but did not, or only marginally, affect the largely beta-1 mediated inotropic responses to isoprenaline.

Participants / model
10 healthy men (mean age 25.3)
Treatment
Oral terbutaline with oral ketotifen or placebo
Follow-up
2 weeks of terbutaline; ketotifen for 3 weeks
Study design
Single-blind randomized placebo-controlled crossover study; systolic time intervals
Funding
not stated in the source

Cardiac endpoints like these are the closest this literature comes to muscle. No study measured skeletal muscle.

Read the original source
Asthma study: no effect of ketotifen on salbutamol responses

Randomized controlled trial

Gove RI et al. Eur J Clin Pharmacol. 1988;34(6):585-9. PMID 2844549.

Ketotifen for one month did not change the spirometric, plasma potassium, or serum glucose responses to nebulized salbutamol, or the skin wheal response to local salbutamol, compared with placebo. The authors concluded that ketotifen at the doses studied had no demonstrable effect on the beta-adrenergic system in asthma.

Participants / model
Patients with asthma (number not stated in the abstract)
Treatment
Ketotifen 1 mg twice daily for one month; nebulized and intradermal salbutamol
Follow-up
One month
Study design
Double-blind controlled study
Funding
not stated in the source

A null result in asthma patients, which differs from the healthy-volunteer findings.

Read the original source
Clenbuterol with ketotifen in asthma: lymphocyte cAMP rose, numbers not stated

Human study

Huszar E et al. Z Erkr Atmungsorgane. 1990;175(3):141-6. PMID 1964319.

In asthmatic patients treated with clenbuterol (Spiropent) for 3 months, lymphocyte beta-adrenergic function (isoproterenol-stimulated cAMP) did not differ from healthy controls. After one week of ketotifen added to clenbuterol it rose above both the clenbuterol-alone values and the healthy controls.

Participants / model
Asthmatic patients and healthy controls (numbers not stated in the truncated abstract)
Treatment
Clenbuterol for 3 months, then ketotifen with clenbuterol for 1 week (routes and doses not stated in the abstract)
Follow-up
3 months of clenbuterol, then 1 week with ketotifen added
Study design
Clinical study of lymphocyte receptor function and plasma TXB2
Funding
not stated in the source

A human study of ketotifen with clenbuterol, though in asthma and with a lymphocyte marker, not a fat, muscle, or performance outcome. The abstract is truncated and gives no sample size or doses.

Read the original source
Fatty liver pilot: 60 adults, 6 months, versus vitamin E, no change in weight or BMI

Randomized controlled trial

Aldossary KM et al. Drug Des Devel Ther. 2026;20:593561. PMID 42039690.

Ketotifen reduced hepatic steatosis and fibrosis scores, HOMA-IR, fasting glucose and insulin, AST, TNF-alpha, and MMP-9, and improved hip circumference and waist-stature ratio, but body weight, BMI, lipids, and HbA1c did not differ between groups. Drowsiness was the most common adverse event.

Participants / model
60 adults with non-alcoholic fatty liver disease
Treatment
Ketotifen versus vitamin E for 6 months (route and dose not stated in the abstract)
Follow-up
6 months
Study design
Randomized pilot trial
Funding
not stated in the source

The comparator was vitamin E, not placebo. NCT05616442 is registered as a completed phase 4 trial of 60 participants with no posted results.

Read the original source
PubChem: ketotifen and ketotifen fumarate identity

Chemical identity record

National Library of Medicine. PubChem compound records CID 3827 (ketotifen) and CID 5282408 (ketotifen fumarate).

Ketotifen base: PubChem CID 3827, C19H19NOS, 309.4 g/mol, CAS 34580-13-7. Ketotifen fumarate, the salt in marketed products: CID 5282408, C23H23NO5S, 425.5 g/mol, CAS 34580-14-8. Strengths may be stated either way: US eye drops are labeled ketotifen 0.025% (fumarate 0.035%), and the UK eye drops contain 0.345 mg fumarate per mL, equal to 0.25 mg ketotifen.

Participants / model
Chemical identity, not a clinical population
Treatment
Base and fumarate salt
Follow-up
Not applicable
Study design
NLM chemical record
Funding
not stated in the source

Identity record only. Supplier oral products have not been compared with either record.

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Why is Ketotifen in A tier?

A fits an approved antiallergic promoted for an off-label use. It is FDA-approved as eye drops, now sold over the counter, and authorized orally in several EU countries. The beta-2 anti-desensitization effect appears in small human studies, but nothing found connects it to fat loss, muscle, or clenbuterol use for body composition, and sedation and weight gain are documented.