Bemethyl

updated

Bemethyl (bemitil) is registered in Russia as Metaprot capsules for raising work capacity and adaptation to extreme conditions, and no FDA-approved product or registered trial turned up. The human evidence is a set of small, mostly Soviet-era Russian-language experiments in extreme conditions, including one operator study with gains in tracking and signal detection, with no athlete trial and no modern independent controlled trial. WADA's 2026 Prohibited List does not name it.

Actoprotector (synthetic adaptogen), a benzimidazole derivative

  • A Russian leaflet for Metaprot capsules lists raising and restoring work capacity, including in extreme conditions such as heavy physical load, hypoxia and overheating, and asthenic disorders.
  • openFDA Drugs@FDA, DailyMed and ClinicalTrials.gov searches on 10 October 2026 found no FDA-approved bemethyl drug and no registered study.
  • In operators during simulated space flight and 56 hours of continuous work, bemithyl gave tracking quality 10% higher, 1.8 times fewer tracking errors and 2.4 times shorter signal detection time than placebo controls (1988 report).
  • A PubMed search on 10 October 2026 returned 28 records, and none tested bemethyl in athletes on a sport-performance endpoint.
  • WADA's 2026 Prohibited List does not name bemethyl, and two abstracts say it entered the WADA Monitoring Program in 2018.
  • In male rats, 60 days of bemithyl lowered sexual activity and the spermatogenesis index.

What is bemethyl, and what is its regulatory status?

Bemethyl (bemitil, 2-(ethylthio)benzimidazole) is registered in Russia as Metaprot capsules for raising work capacity and adaptation to extreme conditions. No FDA-approved product or registered trial turned up, and a Russian registration is not an FDA or EMA review.

A Russian leaflet for Metaprot capsules (ethylthiobenzimidazole hydrobromide monohydrate, registration number LSR-006795/09 dated 26 August 2009, printed with Cyrillic letters) lists raising and restoring work capacity, including in extreme conditions (heavy physical load, hypoxia, overheating), adaptation to extreme factors, asthenic disorders, and, as part of combined therapy, brain injury, meningitis, encephalitis, cerebrovascular disorders and cognitive disorders. The leaflet was read as a copy hosted on a drug-information site, not on the Russian state register. This is a Russian registration, not an FDA or EMA review.

On 10 October 2026, openFDA Drugs@FDA searches on the generic names bemethyl, bemitil, ethylthiobenzimidazole and metaprot each returned no matches, and DailyMed label searches for the same four names returned no labels. ClinicalTrials.gov searches for bemethyl, bemitil, bemithyl, bemityl, metaprot, bemaktor, ethylthiobenzimidazole and 2-ethylthiobenzimidazole returned no studies. The authors of a 2018 study say the active ingredient of Antihot, a dietary supplement sold in Ukraine, is 2-(ethylthio)benzimidazole, also sold as Bemitil, Metaprot and Bemaktor, and developed in the USSR in the 1970s.

Bemethyl as the hydrobromide used in the Russian capsules is PubChem CID 9816609 (C9H11BrN2S, 259.17 g/mol). The free base, 2-(ethylsulfanyl)-1H-benzimidazole, is CID 720878 (C9H10N2S, 178.26 g/mol, CAS 14610-11-8). The names bemethyl, bemitil, bemithyl, Metaprot, Bemaktor and Antihot refer to this substance. Russian label doses are expressed as anhydrous substance of the hydrobromide monohydrate, so a vendor bemethyl sold as free base is not weight-for-weight the same: the free base is about 69% of the hydrobromide by molecular weight.

Metaprot leaflet: work capacity, extreme conditions, asthenia; contraindications

Official label

Russian-language patient leaflet for Metaprot capsules (ethylthiobenzimidazole hydrobromide monohydrate, 50, 125 or 250 mg as anhydrous substance), registration number LSR-006795/09 dated 26 August 2009, printed with Cyrillic letters. Copy hosted on medi.ru.

The leaflet lists raising and restoring work capacity, including in extreme conditions (heavy physical load, hypoxia, overheating), adaptation to extreme factors, asthenic disorders, and, as part of combined therapy, brain injury, meningitis, encephalitis, cerebrovascular disorders and cognitive disorders. It warns of accumulation with continuous dosing. Listed side effects are stomach and liver discomfort, and rarely nausea, vomiting, allergic reactions and headache. Contraindications are hypersensitivity, hypoglycemia, marked liver impairment, pregnancy, lactation, epilepsy, arterial hypertension, glaucoma, ischemic heart disease, arrhythmias, lactose intolerance and childhood. The mechanism text (RNA and protein synthesis, gluconeogenesis, mitochondrial enzymes) is a label description, not a trial result.

Participants / model
Adults
Treatment
Metaprot oral capsules (bemethyl)
Follow-up
Registration dated 26 August 2009
Study design
Russian-language patient leaflet, copy hosted on a drug-information site
Funding
not stated in the source

A Russian registration is not an FDA or EMA review. The copy was read on a commercial drug-information site, not on the Russian state register.

Read the original source
Searches, 10 October 2026: no FDA application, label or registered trial

Regulatory record

U.S. Food and Drug Administration and ClinicalTrials.gov. openFDA Drugs@FDA searches on the generic names bemethyl, bemitil, ethylthiobenzimidazole and metaprot, DailyMed label searches for the same four names, and ClinicalTrials.gov searches for bemethyl, bemitil, bemithyl, bemityl, metaprot, bemaktor, ethylthiobenzimidazole and 2-ethylthiobenzimidazole, all run on 10 October 2026.

Each openFDA Drugs@FDA search returned No matches found, each DailyMed search returned no labels, and the ClinicalTrials.gov searches returned no studies. No FDA-approved bemethyl drug turned up.

Participants / model
Records reviewed, not a population
Treatment
Not applicable
Follow-up
Searches run on 10 October 2026
Study design
Dated regulator and registry search
Funding
not stated in the source

The result covers FDA application and label records and one trial registry only.

Read the original source
Urine detection: 6 healthy volunteers, samples up to 30 days

Human study

Kwiatkowska D et al. Drug Test Anal. 2018;10(11-12):1682-1688. PMID 30346653.

In 6 healthy volunteers (3 men, 3 women, aged 26 to 49) given 6 doses of a supplement over 3 consecutive days, bemitil appeared in urine as the parent compound or its glucuronide, with the glucuronide more abundant and detectable over a wider window, with samples taken for up to 30 days. The authors say 2-(ethylthio)benzimidazole is the active ingredient of Antihot, a dietary supplement sold in Ukraine, and is also sold as Bemitil, Metaprot and Bemaktor, developed in the USSR in the 1970s.

Participants / model
6 healthy volunteers (3 men, 3 women, aged 26 to 49)
Treatment
Oral supplement containing bemitil, 6 doses over 3 days
Follow-up
3 days of dosing, urine samples for up to 30 days
Study design
Clinical analytical study, small
Funding
not stated in the source

The introduction states that research showed bemitil increases physical performance and shortens recovery, but the abstract cites no trial for that statement.

Read the original source
PubChem: bemethyl hydrobromide and free base identity

Chemical identity record

National Library of Medicine. PubChem compound records CID 9816609 (bemethyl hydrobromide) and CID 720878 (bemethyl free base).

Bemethyl as the hydrobromide used in the Russian capsules: PubChem CID 9816609, C9H11BrN2S, 259.17 g/mol, with the CAS-like numbers 63513-71-3 and 109628-14-0 on the record. The free base, 2-(ethylsulfanyl)-1H-benzimidazole: CID 720878, C9H10N2S, 178.26 g/mol, CAS 14610-11-8. The names bemethyl, bemitil, bemithyl, Metaprot, Bemaktor and Antihot refer to this substance.

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

The Russian label doses are expressed as anhydrous substance of the hydrobromide monohydrate, so a vendor bemethyl sold as free base is not weight-for-weight the same: free base is about 69% of the hydrobromide by molecular weight (178.26 of 259.17). Identity record only; it says nothing about efficacy or safety.

Read the original source

What did the human experiments in extreme conditions find?

A 1988 Soviet-era operator experiment found better tracking and faster signal detection than placebo controls, and a small heat-exertion experiment found protection that was best with phenibut, not bemethyl. Both abstracts lack group sizes, and no athlete trial exists.

In operators during simulated space flight and 56 hours of continuous work, bemithyl improved psychophysiological tolerance and work quality compared with placebo controls. Compensatory tracking quality was on average 10% higher, pursuit-tracking errors were 1.8 times fewer, and visual signal detection time was 2.4 times shorter. This is the strongest indexed human result for the mental performance under stress half of the claim, and it comes from a 1988 Soviet-era report. The abstract gives no group size, dose or statistical test.

A single dose of bemethyl 0.5 g or phenibut 0.25 g given before intensive exertion in isolating protective equipment increased thermal resistance, supported oxygen supply and maintained high working capacity under overheating, with the best protection from phenibut, not bemethyl. The abstract gives no group size or placebo. A companion 1997 report lists a placebo arm and bemethyl 0.5 g in volunteers under a heating microclimate, but its result sentence is truncated in PubMed. The under stress evidence here is heat and exertion, not sport.

Operators, 1988: tracking quality 10% higher, signal detection 2.4 times faster

Human study

Bobkov IuG et al. Kosm Biol Aviakosm Med. 1988;22(5):20-3. PMID 3066983.

Bemithyl improved psychophysiological tolerance and work quality compared with placebo controls. Compensatory tracking quality was on average 10% higher, pursuit-tracking errors were 1.8 times fewer, and visual signal detection time was 2.4 times shorter.

Participants / model
Operators in a simulated space-flight experiment with 56 hours of continuous work; group size not stated
Treatment
Oral bemithyl versus placebo; dose not stated in the source
Follow-up
56 hours of continuous work
Study design
Controlled experiment with placebo controls, Soviet-era, Russian-language
Funding
not stated in the source

This is the strongest indexed human result for the mental performance under stress half of the claim, and it comes from a 1988 report. The abstract gives no group size, dose or statistical test.

Read the original source
Heat and exertion: single dose, best protection from phenibut, not bemethyl

Human study

Makarov VI et al. Eksp Klin Farmakol. 1997;60(1):68-71. PMID 9162292.

A single dose of bemethyl 0.5 g or phenibut 0.25 g given before intensive exertion in isolating protective equipment increased thermal resistance, supported oxygen supply, and maintained high working capacity under overheating, with the best protection from phenibut, not bemethyl.

Participants / model
Volunteers exposed to heat and exertion; group size not stated
Treatment
Single oral dose of bemethyl 0.5 g (phenibut 0.25 g in a comparison arm)
Follow-up
Single dose before exertion
Study design
Clinical experiment, small, Russian-language; no placebo stated in the abstract
Funding
not stated in the source

The abstract gives no group size or placebo. A companion 1997 report (PMID 9235216) lists a placebo arm and bemethyl 0.5 g in volunteers under a heating microclimate, but its result sentence is truncated in PubMed. The under stress evidence here is heat and exertion, not sport. Endpoints were thermal state, oxygen exchange and working capacity.

Read the original source

Does bemethyl help people adapt to altitude?

Only a combination study exists. In volunteers moved from 1670 m to 3750 m, Metaprot plus ladasten was associated with faster short-term adaptation than hypoxen alone, and the effect of bemethyl alone cannot be separated.

In volunteers moved from 1670 m to 3750 m, a combination of Metaprot (a bemethyl brand, 0.125 g) and ladasten (0.1 g), which the abstract calls both actoprotectors, was associated with faster short-term adaptation, better tolerance of physical activity and a faster rise in white and red blood cells than hypoxen 0.5 g alone, while the placebo group was still adapting on day 3.

The effect of bemethyl alone cannot be separated, and the abstract gives no group size or effect sizes.

Altitude: Metaprot plus ladasten in volunteers moved from 1670 m to 3750 m

Human study

Kundashev UK et al. Eksp Klin Farmakol. 2014;77(9):32-7. PMID 25365868.

A combination of Metaprot (a bemethyl brand, 0.125 g) and ladasten (0.1 g), which the abstract calls both actoprotectors, was associated with faster short-term adaptation, better tolerance of physical activity, and a faster rise in white and red blood cells than hypoxen 0.5 g alone, while the placebo group was still adapting on day 3.

Participants / model
Volunteers moved from 1670 m to 3750 m; group size not stated
Treatment
Oral Metaprot 0.125 g plus ladasten 0.1 g, versus hypoxen 0.5 g or placebo
Follow-up
Short-term adaptation over the first days at altitude
Study design
Controlled experiment of a combination, Russian-language
Funding
not stated in the source

The effect of bemethyl alone cannot be separated, and the abstract gives no group size or effect sizes. Endpoints were tolerance of physical activity, blood indices and energy-exchange markers.

Read the original source

Where does bemethyl stand with WADA?

The WADA 2026 Prohibited List does not name bemethyl, and two abstracts say it entered the WADA Monitoring Program in 2018. Not being named does not mean it is permitted.

The WADA 2026 Prohibited List, in effect from 1 January 2026, does not name bemethyl, bemitil or its chemical name, and a one-page copy of WADA's 2026 Monitoring Program, hosted by Tennis Ireland and not by WADA, does not list it. Two PubMed abstracts say bemitil or bemethyl entered the WADA Monitoring Program in 2018, and the years between 2018 and 2026 were not examined.

The List's S0 class prohibits at all times any pharmacological substance not covered elsewhere and with no current approval by any governmental regulatory health authority for human therapeutic use. Whether S0 reaches bemethyl depends on its approval status, which is not decided here. Bromantan and mesocarb are named in the stimulant class (S6.A) of the 2026 List, and bemethyl is not. Bemethyl not being named on the 2026 List does not mean it is permitted.

WADA 2026 List does not name bemethyl; monitored from 2018 per two abstracts

Regulatory record

World Anti-Doping Agency. The 2026 Prohibited List, in effect from 1 January 2026. A one-page copy of WADA's 2026 Monitoring Program hosted by Tennis Ireland was also read. Two PubMed abstracts (PMIDs 30346653 and 34445727) state that bemitil or bemethyl entered the WADA Monitoring Program in 2018.

The 2026 Prohibited List does not name bemethyl, bemitil or its chemical name, and the copy of the 2026 Monitoring Program does not list it. Two PubMed abstracts say bemitil or bemethyl entered the WADA Monitoring Program in 2018. The List's S0 class prohibits at all times any pharmacological substance not covered elsewhere and with no current approval by any governmental regulatory health authority for human therapeutic use. Bromantan and mesocarb are named in the stimulant class (S6.A) of the 2026 List.

Participants / model
Not a clinical population
Treatment
Anti-doping rule
Follow-up
2026 List in effect from 1 January 2026; years between 2018 and 2026 not examined
Study design
Official anti-doping list, plus a third-party copy of the monitoring program
Funding
not stated in the source

Bemethyl not being named on the 2026 List does not mean it is permitted. Whether S0 reaches bemethyl depends on its approval status, which is not decided here. The 2026 Monitoring Program was read from a copy hosted by Tennis Ireland, not by WADA.

Read the original source
Urine detection: 6 healthy volunteers, samples up to 30 days

Human study

Kwiatkowska D et al. Drug Test Anal. 2018;10(11-12):1682-1688. PMID 30346653.

In 6 healthy volunteers (3 men, 3 women, aged 26 to 49) given 6 doses of a supplement over 3 consecutive days, bemitil appeared in urine as the parent compound or its glucuronide, with the glucuronide more abundant and detectable over a wider window, with samples taken for up to 30 days. The authors say 2-(ethylthio)benzimidazole is the active ingredient of Antihot, a dietary supplement sold in Ukraine, and is also sold as Bemitil, Metaprot and Bemaktor, developed in the USSR in the 1970s.

Participants / model
6 healthy volunteers (3 men, 3 women, aged 26 to 49)
Treatment
Oral supplement containing bemitil, 6 doses over 3 days
Follow-up
3 days of dosing, urine samples for up to 30 days
Study design
Clinical analytical study, small
Funding
not stated in the source

The introduction states that research showed bemitil increases physical performance and shortens recovery, but the abstract cites no trial for that statement.

Read the original source

Is bemethyl the reference actoprotector for performance under stress?

The claim matches the Russian leaflet and a few small controlled experiments in extreme conditions, but the reference status rests on one narrative review and a regional label. No study tested bemethyl in athletes on a sport-performance endpoint, and a PubMed search on 10 October 2026 returned 28 records with no randomized, registered or modern trial in healthy people.

Sellers call bemethyl (bemitil) the reference actoprotector, giving better physical and mental performance under stress. A 2012 narrative review describes actoprotectors as synthetic adaptogens that raise resistance to physical load without raising oxygen consumption or heat production, names bemitil and bromantane as the main representatives, and says they can be used in normal or extreme conditions with high efficiency and safety. It is a narrative review without pooled effect sizes, and the efficiency and safety statements are the authors' own.

A PubMed search on 10 October 2026 for bemethyl and its other names with athletes, sport, physical performance, work capacity, volunteers, placebo or healthy returned 28 records, and every title and the abstracts of the human studies were read. No study tested bemethyl in athletes on a sport-performance endpoint, and no randomized, registered or modern-era trial of it in healthy people turned up. The human work was a set of Russian-language experiments in operators, heat, carbon monoxide, altitude and static load, mostly from 1988 to 2000 with one from 2014, most without group sizes in the abstract, and two used combinations. A broader bemethyl search returned 105 records, and the titles of the first 60 only were read.

The evidence gap is the lack of any contemporary independent controlled trial of bemethyl alone.

2012 narrative review: bemitil and bromantane as the main actoprotectors

Narrative review

Oliynyk S et al. Biomol Ther (Seoul). 2012;20(5):446-56. PMID 24009833.

The review describes actoprotectors as synthetic adaptogens that raise resistance to physical load without raising oxygen consumption or heat production, names bemitil and bromantane as the main representatives, and says they can be used in normal or extreme conditions with high efficiency and safety.

Participants / model
Narrative summary; the abstract does not say which studies it covers
Treatment
Not applicable
Follow-up
Not applicable
Study design
Narrative review without pooled effect sizes
Funding
not stated in the source

This is the source of the reference actoprotector framing. The efficiency and safety statements are the authors' own.

Read the original source
PubMed search, 10 October 2026: 28 records, no athlete or modern trial

PubMed search record

PubMed search run on 10 October 2026: (bemethyl OR bemitil OR bemithyl OR bemityl OR bemetil OR metaprot OR bemaktor) AND (athletes OR sport OR physical performance OR work capacity OR volunteers OR placebo OR healthy). 28 records returned.

The search returned 28 records, and every title and the abstracts of the human studies were read. No study tested bemethyl in athletes on a sport-performance endpoint, and no randomized, registered or modern-era trial of it in healthy people turned up. The human work was a set of Russian-language experiments in operators, heat, carbon monoxide, altitude and static load, mostly from 1988 to 2000 with one from 2014, most without group sizes in the abstract, and two used combinations. A broader bemethyl search returned 105 records, and the titles of the first 60 only were read.

Participants / model
Records returned, not a population
Treatment
Not applicable
Follow-up
Search run on 10 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 evidence gap is the lack of any contemporary independent controlled trial of bemethyl alone.

Read the original source

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

The leaflet's mechanism text, covering RNA and protein synthesis, gluconeogenesis and mitochondrial enzymes, is a label description, not a trial result. After a single 250 mg capsule, serum peaked at 0.91 microgram/mL at 1.06 hours, and the leaflet warns of accumulation with continuous dosing.

The Russian leaflet's mechanism text, covering RNA and protein synthesis, gluconeogenesis and mitochondrial enzymes, is a label description, not a trial result. In rats, bemithyl induced liver cytochrome P-450 enzymes, with effects also seen in human lymphocytes in vitro, which is a possible drug-interaction signal.

After a single 250 mg Metaprot capsule in healthy adult volunteers, serum ethylthiobenzimidazole peaked at 0.91 microgram/mL (SD 1.05) at 1.06 hours (SD 0.16), with a polymodal spread of parameters across the group. The abstract does not give the group size, half-life or exposure after repeat doses, and the leaflet warns of accumulation with continuous dosing.

In 6 healthy volunteers (3 men, 3 women, aged 26 to 49) given 6 doses of a supplement over 3 consecutive days, bemitil appeared in urine as the parent compound or its glucuronide, with the glucuronide more abundant and detectable over a wider window, with samples taken for up to 30 days.

Metaprot leaflet: work capacity, extreme conditions, asthenia; contraindications

Official label

Russian-language patient leaflet for Metaprot capsules (ethylthiobenzimidazole hydrobromide monohydrate, 50, 125 or 250 mg as anhydrous substance), registration number LSR-006795/09 dated 26 August 2009, printed with Cyrillic letters. Copy hosted on medi.ru.

The leaflet lists raising and restoring work capacity, including in extreme conditions (heavy physical load, hypoxia, overheating), adaptation to extreme factors, asthenic disorders, and, as part of combined therapy, brain injury, meningitis, encephalitis, cerebrovascular disorders and cognitive disorders. It warns of accumulation with continuous dosing. Listed side effects are stomach and liver discomfort, and rarely nausea, vomiting, allergic reactions and headache. Contraindications are hypersensitivity, hypoglycemia, marked liver impairment, pregnancy, lactation, epilepsy, arterial hypertension, glaucoma, ischemic heart disease, arrhythmias, lactose intolerance and childhood. The mechanism text (RNA and protein synthesis, gluconeogenesis, mitochondrial enzymes) is a label description, not a trial result.

Participants / model
Adults
Treatment
Metaprot oral capsules (bemethyl)
Follow-up
Registration dated 26 August 2009
Study design
Russian-language patient leaflet, copy hosted on a drug-information site
Funding
not stated in the source

A Russian registration is not an FDA or EMA review. The copy was read on a commercial drug-information site, not on the Russian state register.

Read the original source
Rats: 60 days of bemithyl lowered sexual activity and spermatogenesis index

Animal study

Bugaeva LI et al. Eksp Klin Farmakol. 2006;69(1):38-41. PMID 16579058.

In male rats, 60 days of bemithyl lowered male sexual activity and the spermatogenesis index, whereas 3 days of dosing raised them. Other rat work adds an oral LD50 of 581.48 mg/kg (PMID 11202514) and induction of liver cytochrome P-450 enzymes in rats, with effects also seen in human lymphocytes in vitro (PMID 12227093), which is a possible drug-interaction signal. One rat study of dosing from day 6 to 16 of pregnancy found fewer post-implantation fetal deaths (PMID 17402591).

Participants / model
Male rats
Treatment
Oral bemithyl for 3 days or 60 days; dose not stated in the source
Follow-up
3 days or 60 days
Study design
Original animal study
Funding
not stated in the source

These are animal findings and are not shown to apply to people at label doses. No human safety study turned up in the records reviewed to put beside them. Endpoints were sexual behavior and the spermatogenesis index.

Read the original source
Single-dose PK: serum peak 0.91 microgram/mL at 1.06 hours

Human study

Kibal'chich DA et al. Eksp Klin Farmakol. 2011;74(6):30-2. PMID 21870773.

After a single 250 mg Metaprot capsule in healthy adult volunteers, serum ethylthiobenzimidazole peaked at 0.91 microgram/mL (SD 1.05) at 1.06 hours (SD 0.16), with a polymodal spread of parameters across the group.

Participants / model
Healthy adult volunteers; group size not stated in the abstract
Treatment
Oral Metaprot 250 mg capsule, single dose
Follow-up
Single dose
Study design
Clinical pharmacokinetic study, small, Russian-language
Funding
not stated in the source

The abstract does not give the group size, half-life, or exposure after repeat doses, and the leaflet separately warns of accumulation.

Read the original source
Urine detection: 6 healthy volunteers, samples up to 30 days

Human study

Kwiatkowska D et al. Drug Test Anal. 2018;10(11-12):1682-1688. PMID 30346653.

In 6 healthy volunteers (3 men, 3 women, aged 26 to 49) given 6 doses of a supplement over 3 consecutive days, bemitil appeared in urine as the parent compound or its glucuronide, with the glucuronide more abundant and detectable over a wider window, with samples taken for up to 30 days. The authors say 2-(ethylthio)benzimidazole is the active ingredient of Antihot, a dietary supplement sold in Ukraine, and is also sold as Bemitil, Metaprot and Bemaktor, developed in the USSR in the 1970s.

Participants / model
6 healthy volunteers (3 men, 3 women, aged 26 to 49)
Treatment
Oral supplement containing bemitil, 6 doses over 3 days
Follow-up
3 days of dosing, urine samples for up to 30 days
Study design
Clinical analytical study, small
Funding
not stated in the source

The introduction states that research showed bemitil increases physical performance and shortens recovery, but the abstract cites no trial for that statement.

Read the original source

What risks and warnings are reported?

The Russian leaflet lists stomach and liver discomfort and rare allergic reactions, warns of accumulation, and contraindicates hypertension, ischemic heart disease, arrhythmias, epilepsy, glaucoma and pregnancy among others. No human safety study turned up, and rats showed a spermatogenesis signal with 60 days of dosing.

The Russian leaflet lists stomach and liver discomfort, and rarely nausea, vomiting, allergic reactions and headache, as side effects, and warns of accumulation with continuous dosing. Contraindications are hypersensitivity, hypoglycemia, marked liver impairment, pregnancy, lactation, epilepsy, arterial hypertension, glaucoma, ischemic heart disease, arrhythmias, lactose intolerance and childhood.

In male rats, 60 days of bemithyl lowered male sexual activity and the spermatogenesis index, whereas 3 days of dosing raised them. Other rat work reports an oral LD50 of 581.48 mg/kg, induction of liver cytochrome P-450 enzymes with effects also seen in human lymphocytes in vitro, and fewer post-implantation fetal deaths in one study of dosing from day 6 to 16 of pregnancy.

These are animal findings and are not shown to apply to people at label doses, but no human safety study turned up in the records reviewed to put beside them.

Metaprot leaflet: work capacity, extreme conditions, asthenia; contraindications

Official label

Russian-language patient leaflet for Metaprot capsules (ethylthiobenzimidazole hydrobromide monohydrate, 50, 125 or 250 mg as anhydrous substance), registration number LSR-006795/09 dated 26 August 2009, printed with Cyrillic letters. Copy hosted on medi.ru.

The leaflet lists raising and restoring work capacity, including in extreme conditions (heavy physical load, hypoxia, overheating), adaptation to extreme factors, asthenic disorders, and, as part of combined therapy, brain injury, meningitis, encephalitis, cerebrovascular disorders and cognitive disorders. It warns of accumulation with continuous dosing. Listed side effects are stomach and liver discomfort, and rarely nausea, vomiting, allergic reactions and headache. Contraindications are hypersensitivity, hypoglycemia, marked liver impairment, pregnancy, lactation, epilepsy, arterial hypertension, glaucoma, ischemic heart disease, arrhythmias, lactose intolerance and childhood. The mechanism text (RNA and protein synthesis, gluconeogenesis, mitochondrial enzymes) is a label description, not a trial result.

Participants / model
Adults
Treatment
Metaprot oral capsules (bemethyl)
Follow-up
Registration dated 26 August 2009
Study design
Russian-language patient leaflet, copy hosted on a drug-information site
Funding
not stated in the source

A Russian registration is not an FDA or EMA review. The copy was read on a commercial drug-information site, not on the Russian state register.

Read the original source
Rats: 60 days of bemithyl lowered sexual activity and spermatogenesis index

Animal study

Bugaeva LI et al. Eksp Klin Farmakol. 2006;69(1):38-41. PMID 16579058.

In male rats, 60 days of bemithyl lowered male sexual activity and the spermatogenesis index, whereas 3 days of dosing raised them. Other rat work adds an oral LD50 of 581.48 mg/kg (PMID 11202514) and induction of liver cytochrome P-450 enzymes in rats, with effects also seen in human lymphocytes in vitro (PMID 12227093), which is a possible drug-interaction signal. One rat study of dosing from day 6 to 16 of pregnancy found fewer post-implantation fetal deaths (PMID 17402591).

Participants / model
Male rats
Treatment
Oral bemithyl for 3 days or 60 days; dose not stated in the source
Follow-up
3 days or 60 days
Study design
Original animal study
Funding
not stated in the source

These are animal findings and are not shown to apply to people at label doses. No human safety study turned up in the records reviewed to put beside them. Endpoints were sexual behavior and the spermatogenesis index.

Read the original source

Why does bemethyl sit in C tier?

C fits a drug registered in Russia for performance and asthenia uses, with placebo-referenced human experiments in extreme conditions but thin evidence by modern standards: Soviet-era or small Russian-language reports, two combination studies, no athlete trial, no registered trial and no FDA or EMA review.

The C reflects that positive placebo-referenced human findings exist, including one operator study with measurable gains in tracking and signal detection. It stops short of a higher grade because there is no modern controlled trial, human safety data are minimal, and the rat data include a spermatogenesis signal with chronic dosing.

For the supplier's claim, better physical and mental performance under stress matches the Russian leaflet and the small controlled experiments in extreme conditions. The reference status rests on one narrative review and a regional label, with no athlete or contemporary trial.

Metaprot leaflet: work capacity, extreme conditions, asthenia; contraindications

Official label

Russian-language patient leaflet for Metaprot capsules (ethylthiobenzimidazole hydrobromide monohydrate, 50, 125 or 250 mg as anhydrous substance), registration number LSR-006795/09 dated 26 August 2009, printed with Cyrillic letters. Copy hosted on medi.ru.

The leaflet lists raising and restoring work capacity, including in extreme conditions (heavy physical load, hypoxia, overheating), adaptation to extreme factors, asthenic disorders, and, as part of combined therapy, brain injury, meningitis, encephalitis, cerebrovascular disorders and cognitive disorders. It warns of accumulation with continuous dosing. Listed side effects are stomach and liver discomfort, and rarely nausea, vomiting, allergic reactions and headache. Contraindications are hypersensitivity, hypoglycemia, marked liver impairment, pregnancy, lactation, epilepsy, arterial hypertension, glaucoma, ischemic heart disease, arrhythmias, lactose intolerance and childhood. The mechanism text (RNA and protein synthesis, gluconeogenesis, mitochondrial enzymes) is a label description, not a trial result.

Participants / model
Adults
Treatment
Metaprot oral capsules (bemethyl)
Follow-up
Registration dated 26 August 2009
Study design
Russian-language patient leaflet, copy hosted on a drug-information site
Funding
not stated in the source

A Russian registration is not an FDA or EMA review. The copy was read on a commercial drug-information site, not on the Russian state register.

Read the original source
Operators, 1988: tracking quality 10% higher, signal detection 2.4 times faster

Human study

Bobkov IuG et al. Kosm Biol Aviakosm Med. 1988;22(5):20-3. PMID 3066983.

Bemithyl improved psychophysiological tolerance and work quality compared with placebo controls. Compensatory tracking quality was on average 10% higher, pursuit-tracking errors were 1.8 times fewer, and visual signal detection time was 2.4 times shorter.

Participants / model
Operators in a simulated space-flight experiment with 56 hours of continuous work; group size not stated
Treatment
Oral bemithyl versus placebo; dose not stated in the source
Follow-up
56 hours of continuous work
Study design
Controlled experiment with placebo controls, Soviet-era, Russian-language
Funding
not stated in the source

This is the strongest indexed human result for the mental performance under stress half of the claim, and it comes from a 1988 report. The abstract gives no group size, dose or statistical test.

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Heat and exertion: single dose, best protection from phenibut, not bemethyl

Human study

Makarov VI et al. Eksp Klin Farmakol. 1997;60(1):68-71. PMID 9162292.

A single dose of bemethyl 0.5 g or phenibut 0.25 g given before intensive exertion in isolating protective equipment increased thermal resistance, supported oxygen supply, and maintained high working capacity under overheating, with the best protection from phenibut, not bemethyl.

Participants / model
Volunteers exposed to heat and exertion; group size not stated
Treatment
Single oral dose of bemethyl 0.5 g (phenibut 0.25 g in a comparison arm)
Follow-up
Single dose before exertion
Study design
Clinical experiment, small, Russian-language; no placebo stated in the abstract
Funding
not stated in the source

The abstract gives no group size or placebo. A companion 1997 report (PMID 9235216) lists a placebo arm and bemethyl 0.5 g in volunteers under a heating microclimate, but its result sentence is truncated in PubMed. The under stress evidence here is heat and exertion, not sport. Endpoints were thermal state, oxygen exchange and working capacity.

Read the original source
Altitude: Metaprot plus ladasten in volunteers moved from 1670 m to 3750 m

Human study

Kundashev UK et al. Eksp Klin Farmakol. 2014;77(9):32-7. PMID 25365868.

A combination of Metaprot (a bemethyl brand, 0.125 g) and ladasten (0.1 g), which the abstract calls both actoprotectors, was associated with faster short-term adaptation, better tolerance of physical activity, and a faster rise in white and red blood cells than hypoxen 0.5 g alone, while the placebo group was still adapting on day 3.

Participants / model
Volunteers moved from 1670 m to 3750 m; group size not stated
Treatment
Oral Metaprot 0.125 g plus ladasten 0.1 g, versus hypoxen 0.5 g or placebo
Follow-up
Short-term adaptation over the first days at altitude
Study design
Controlled experiment of a combination, Russian-language
Funding
not stated in the source

The effect of bemethyl alone cannot be separated, and the abstract gives no group size or effect sizes. Endpoints were tolerance of physical activity, blood indices and energy-exchange markers.

Read the original source
PubMed search, 10 October 2026: 28 records, no athlete or modern trial

PubMed search record

PubMed search run on 10 October 2026: (bemethyl OR bemitil OR bemithyl OR bemityl OR bemetil OR metaprot OR bemaktor) AND (athletes OR sport OR physical performance OR work capacity OR volunteers OR placebo OR healthy). 28 records returned.

The search returned 28 records, and every title and the abstracts of the human studies were read. No study tested bemethyl in athletes on a sport-performance endpoint, and no randomized, registered or modern-era trial of it in healthy people turned up. The human work was a set of Russian-language experiments in operators, heat, carbon monoxide, altitude and static load, mostly from 1988 to 2000 with one from 2014, most without group sizes in the abstract, and two used combinations. A broader bemethyl search returned 105 records, and the titles of the first 60 only were read.

Participants / model
Records returned, not a population
Treatment
Not applicable
Follow-up
Search run on 10 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 evidence gap is the lack of any contemporary independent controlled trial of bemethyl alone.

Read the original source
Searches, 10 October 2026: no FDA application, label or registered trial

Regulatory record

U.S. Food and Drug Administration and ClinicalTrials.gov. openFDA Drugs@FDA searches on the generic names bemethyl, bemitil, ethylthiobenzimidazole and metaprot, DailyMed label searches for the same four names, and ClinicalTrials.gov searches for bemethyl, bemitil, bemithyl, bemityl, metaprot, bemaktor, ethylthiobenzimidazole and 2-ethylthiobenzimidazole, all run on 10 October 2026.

Each openFDA Drugs@FDA search returned No matches found, each DailyMed search returned no labels, and the ClinicalTrials.gov searches returned no studies. No FDA-approved bemethyl drug turned up.

Participants / model
Records reviewed, not a population
Treatment
Not applicable
Follow-up
Searches run on 10 October 2026
Study design
Dated regulator and registry search
Funding
not stated in the source

The result covers FDA application and label records and one trial registry only.

Read the original source
2012 narrative review: bemitil and bromantane as the main actoprotectors

Narrative review

Oliynyk S et al. Biomol Ther (Seoul). 2012;20(5):446-56. PMID 24009833.

The review describes actoprotectors as synthetic adaptogens that raise resistance to physical load without raising oxygen consumption or heat production, names bemitil and bromantane as the main representatives, and says they can be used in normal or extreme conditions with high efficiency and safety.

Participants / model
Narrative summary; the abstract does not say which studies it covers
Treatment
Not applicable
Follow-up
Not applicable
Study design
Narrative review without pooled effect sizes
Funding
not stated in the source

This is the source of the reference actoprotector framing. The efficiency and safety statements are the authors' own.

Read the original source

Studies and sources

Metaprot leaflet: work capacity, extreme conditions, asthenia; contraindications

Official label

Russian-language patient leaflet for Metaprot capsules (ethylthiobenzimidazole hydrobromide monohydrate, 50, 125 or 250 mg as anhydrous substance), registration number LSR-006795/09 dated 26 August 2009, printed with Cyrillic letters. Copy hosted on medi.ru.

The leaflet lists raising and restoring work capacity, including in extreme conditions (heavy physical load, hypoxia, overheating), adaptation to extreme factors, asthenic disorders, and, as part of combined therapy, brain injury, meningitis, encephalitis, cerebrovascular disorders and cognitive disorders. It warns of accumulation with continuous dosing. Listed side effects are stomach and liver discomfort, and rarely nausea, vomiting, allergic reactions and headache. Contraindications are hypersensitivity, hypoglycemia, marked liver impairment, pregnancy, lactation, epilepsy, arterial hypertension, glaucoma, ischemic heart disease, arrhythmias, lactose intolerance and childhood. The mechanism text (RNA and protein synthesis, gluconeogenesis, mitochondrial enzymes) is a label description, not a trial result.

Participants / model
Adults
Treatment
Metaprot oral capsules (bemethyl)
Follow-up
Registration dated 26 August 2009
Study design
Russian-language patient leaflet, copy hosted on a drug-information site
Funding
not stated in the source

A Russian registration is not an FDA or EMA review. The copy was read on a commercial drug-information site, not on the Russian state register.

Read the original source
WADA 2026 List does not name bemethyl; monitored from 2018 per two abstracts

Regulatory record

World Anti-Doping Agency. The 2026 Prohibited List, in effect from 1 January 2026. A one-page copy of WADA's 2026 Monitoring Program hosted by Tennis Ireland was also read. Two PubMed abstracts (PMIDs 30346653 and 34445727) state that bemitil or bemethyl entered the WADA Monitoring Program in 2018.

The 2026 Prohibited List does not name bemethyl, bemitil or its chemical name, and the copy of the 2026 Monitoring Program does not list it. Two PubMed abstracts say bemitil or bemethyl entered the WADA Monitoring Program in 2018. The List's S0 class prohibits at all times any pharmacological substance not covered elsewhere and with no current approval by any governmental regulatory health authority for human therapeutic use. Bromantan and mesocarb are named in the stimulant class (S6.A) of the 2026 List.

Participants / model
Not a clinical population
Treatment
Anti-doping rule
Follow-up
2026 List in effect from 1 January 2026; years between 2018 and 2026 not examined
Study design
Official anti-doping list, plus a third-party copy of the monitoring program
Funding
not stated in the source

Bemethyl not being named on the 2026 List does not mean it is permitted. Whether S0 reaches bemethyl depends on its approval status, which is not decided here. The 2026 Monitoring Program was read from a copy hosted by Tennis Ireland, not by WADA.

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Urine detection: 6 healthy volunteers, samples up to 30 days

Human study

Kwiatkowska D et al. Drug Test Anal. 2018;10(11-12):1682-1688. PMID 30346653.

In 6 healthy volunteers (3 men, 3 women, aged 26 to 49) given 6 doses of a supplement over 3 consecutive days, bemitil appeared in urine as the parent compound or its glucuronide, with the glucuronide more abundant and detectable over a wider window, with samples taken for up to 30 days. The authors say 2-(ethylthio)benzimidazole is the active ingredient of Antihot, a dietary supplement sold in Ukraine, and is also sold as Bemitil, Metaprot and Bemaktor, developed in the USSR in the 1970s.

Participants / model
6 healthy volunteers (3 men, 3 women, aged 26 to 49)
Treatment
Oral supplement containing bemitil, 6 doses over 3 days
Follow-up
3 days of dosing, urine samples for up to 30 days
Study design
Clinical analytical study, small
Funding
not stated in the source

The introduction states that research showed bemitil increases physical performance and shortens recovery, but the abstract cites no trial for that statement.

Read the original source
2012 narrative review: bemitil and bromantane as the main actoprotectors

Narrative review

Oliynyk S et al. Biomol Ther (Seoul). 2012;20(5):446-56. PMID 24009833.

The review describes actoprotectors as synthetic adaptogens that raise resistance to physical load without raising oxygen consumption or heat production, names bemitil and bromantane as the main representatives, and says they can be used in normal or extreme conditions with high efficiency and safety.

Participants / model
Narrative summary; the abstract does not say which studies it covers
Treatment
Not applicable
Follow-up
Not applicable
Study design
Narrative review without pooled effect sizes
Funding
not stated in the source

This is the source of the reference actoprotector framing. The efficiency and safety statements are the authors' own.

Read the original source
Operators, 1988: tracking quality 10% higher, signal detection 2.4 times faster

Human study

Bobkov IuG et al. Kosm Biol Aviakosm Med. 1988;22(5):20-3. PMID 3066983.

Bemithyl improved psychophysiological tolerance and work quality compared with placebo controls. Compensatory tracking quality was on average 10% higher, pursuit-tracking errors were 1.8 times fewer, and visual signal detection time was 2.4 times shorter.

Participants / model
Operators in a simulated space-flight experiment with 56 hours of continuous work; group size not stated
Treatment
Oral bemithyl versus placebo; dose not stated in the source
Follow-up
56 hours of continuous work
Study design
Controlled experiment with placebo controls, Soviet-era, Russian-language
Funding
not stated in the source

This is the strongest indexed human result for the mental performance under stress half of the claim, and it comes from a 1988 report. The abstract gives no group size, dose or statistical test.

Read the original source
Heat and exertion: single dose, best protection from phenibut, not bemethyl

Human study

Makarov VI et al. Eksp Klin Farmakol. 1997;60(1):68-71. PMID 9162292.

A single dose of bemethyl 0.5 g or phenibut 0.25 g given before intensive exertion in isolating protective equipment increased thermal resistance, supported oxygen supply, and maintained high working capacity under overheating, with the best protection from phenibut, not bemethyl.

Participants / model
Volunteers exposed to heat and exertion; group size not stated
Treatment
Single oral dose of bemethyl 0.5 g (phenibut 0.25 g in a comparison arm)
Follow-up
Single dose before exertion
Study design
Clinical experiment, small, Russian-language; no placebo stated in the abstract
Funding
not stated in the source

The abstract gives no group size or placebo. A companion 1997 report (PMID 9235216) lists a placebo arm and bemethyl 0.5 g in volunteers under a heating microclimate, but its result sentence is truncated in PubMed. The under stress evidence here is heat and exertion, not sport. Endpoints were thermal state, oxygen exchange and working capacity.

Read the original source
Altitude: Metaprot plus ladasten in volunteers moved from 1670 m to 3750 m

Human study

Kundashev UK et al. Eksp Klin Farmakol. 2014;77(9):32-7. PMID 25365868.

A combination of Metaprot (a bemethyl brand, 0.125 g) and ladasten (0.1 g), which the abstract calls both actoprotectors, was associated with faster short-term adaptation, better tolerance of physical activity, and a faster rise in white and red blood cells than hypoxen 0.5 g alone, while the placebo group was still adapting on day 3.

Participants / model
Volunteers moved from 1670 m to 3750 m; group size not stated
Treatment
Oral Metaprot 0.125 g plus ladasten 0.1 g, versus hypoxen 0.5 g or placebo
Follow-up
Short-term adaptation over the first days at altitude
Study design
Controlled experiment of a combination, Russian-language
Funding
not stated in the source

The effect of bemethyl alone cannot be separated, and the abstract gives no group size or effect sizes. Endpoints were tolerance of physical activity, blood indices and energy-exchange markers.

Read the original source
Single-dose PK: serum peak 0.91 microgram/mL at 1.06 hours

Human study

Kibal'chich DA et al. Eksp Klin Farmakol. 2011;74(6):30-2. PMID 21870773.

After a single 250 mg Metaprot capsule in healthy adult volunteers, serum ethylthiobenzimidazole peaked at 0.91 microgram/mL (SD 1.05) at 1.06 hours (SD 0.16), with a polymodal spread of parameters across the group.

Participants / model
Healthy adult volunteers; group size not stated in the abstract
Treatment
Oral Metaprot 250 mg capsule, single dose
Follow-up
Single dose
Study design
Clinical pharmacokinetic study, small, Russian-language
Funding
not stated in the source

The abstract does not give the group size, half-life, or exposure after repeat doses, and the leaflet separately warns of accumulation.

Read the original source
Rats: 60 days of bemithyl lowered sexual activity and spermatogenesis index

Animal study

Bugaeva LI et al. Eksp Klin Farmakol. 2006;69(1):38-41. PMID 16579058.

In male rats, 60 days of bemithyl lowered male sexual activity and the spermatogenesis index, whereas 3 days of dosing raised them. Other rat work adds an oral LD50 of 581.48 mg/kg (PMID 11202514) and induction of liver cytochrome P-450 enzymes in rats, with effects also seen in human lymphocytes in vitro (PMID 12227093), which is a possible drug-interaction signal. One rat study of dosing from day 6 to 16 of pregnancy found fewer post-implantation fetal deaths (PMID 17402591).

Participants / model
Male rats
Treatment
Oral bemithyl for 3 days or 60 days; dose not stated in the source
Follow-up
3 days or 60 days
Study design
Original animal study
Funding
not stated in the source

These are animal findings and are not shown to apply to people at label doses. No human safety study turned up in the records reviewed to put beside them. Endpoints were sexual behavior and the spermatogenesis index.

Read the original source
PubChem: bemethyl hydrobromide and free base identity

Chemical identity record

National Library of Medicine. PubChem compound records CID 9816609 (bemethyl hydrobromide) and CID 720878 (bemethyl free base).

Bemethyl as the hydrobromide used in the Russian capsules: PubChem CID 9816609, C9H11BrN2S, 259.17 g/mol, with the CAS-like numbers 63513-71-3 and 109628-14-0 on the record. The free base, 2-(ethylsulfanyl)-1H-benzimidazole: CID 720878, C9H10N2S, 178.26 g/mol, CAS 14610-11-8. The names bemethyl, bemitil, bemithyl, Metaprot, Bemaktor and Antihot refer to this substance.

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

The Russian label doses are expressed as anhydrous substance of the hydrobromide monohydrate, so a vendor bemethyl sold as free base is not weight-for-weight the same: free base is about 69% of the hydrobromide by molecular weight (178.26 of 259.17). Identity record only; it says nothing about efficacy or safety.

Read the original source

Why is Bemethyl in C tier?

C fits a drug registered in Russia for performance and asthenia uses, with placebo-referenced human experiments in extreme conditions, including one operator study with measurable gains. The evidence is thin by modern standards: Soviet-era or small Russian-language reports with group sizes missing from the abstracts, two combination studies, no athlete trial, no registered trial and no FDA or EMA review. Human safety data are minimal, and rats showed a spermatogenesis signal with 60 days of dosing.