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Bemethyl (Bemitil / Metaprot)

Synthetic — benzimidazole actoprotector
Evidence Level
Preliminary
3 Clinical Trials
6 Documented Benefits
1/5 Evidence Score

Bemethyl is not a dietary supplement. It is a synthetic benzimidazole drug, developed in the 1970s at the S.M. Kirov Military Medical Academy in Leningrad and classed by its developers as an 'actoprotector', meaning a compound intended to raise physical and mental work capacity under stress without raising oxygen consumption. It was given to Soviet cosmonauts, to the USSR team preparing for the 1980 Moscow Olympics, and to Soviet soldiers. Official manufacture stopped when the USSR dissolved in 1991. It is sold today in a small number of post-Soviet countries under names including Bemitil, Metaprot and Bemaktor, and in Ukraine as a product called Antihot. It has never been approved by the FDA, it does not appear anywhere in FDA's Dietary Supplement Ingredient Directory, and as a synthetic drug with no record of use in the American food supply before 1994 it is unlikely to qualify as a lawful dietary ingredient at all. On doping: the World Anti-Doping Agency placed bemitil on its Monitoring Program, in and out of competition, from 2018 through 2021, dropped it from the 2022 program, and has not named it on the Prohibited List through 2026. Almost all published human data are small Soviet-era Russian-language studies. This page exists so that people who encounter bemethyl know what it is, not as a recommendation to take it.

Studied Dose Labelling describes 250 to 500 mg once or twice daily in courses of three to five days; no dose or schedule for athletic use has been established in any published study.
Active Compound Bemethyl (2-(ethylsulfanyl)-1H-benzimidazole hydrobromide; bemitil, metaprot, bemiton, bemactor, antihot, ethylthiobenzimidazole) - synthetic benzimidazole derivative.

Benefits

Fatigue and low stamina (one 1988 Soviet comparison study)

The main human report is a 1988 Russian-language paper covering 130 patients treated for asthenic states within borderline neuropsychiatric conditions, in which bemitil was compared with two other drugs, piracetam and pyritinol, and was described as acting faster and more broadly on fatigue symptoms. The published abstract does not say that patients were randomised, that anyone was blinded, or that there was a placebo group, and no English full text exists, so the size of any effect cannot be checked. The same author group, and apparently the same patient series, produced the 1986 pharmacokinetic paper also cited on this page, so these are not two independent findings.

Supported by Trial 1

Work capacity during prolonged strain (one small Soviet operator study)

In a 1988 Soviet study, operators working 56 continuous hours in a simulated spaceflight environment did about 10 percent better on compensatory tracking, made 1.8 times fewer pursuit-tracking errors and detected visual signals 2.4 times faster than placebo controls. The report does not state how many people took part, and nothing like it has been repeated outside the former USSR. Bemethyl's use by cosmonauts, by the 1980 Olympic team and by the Soviet army is history, not evidence that it works.

Supported by Trial 1, Trial 2

Hypoxia tolerance and altitude performance

The one placebo-controlled altitude study, presented in NATO meeting proceedings rather than a peer-reviewed journal, gave 750 mg per day in five-day courses to 7 soldiers at 2,800 m against 8 on placebo, and to 10 soldiers with low hypoxia tolerance at 3,600 m against 10 on placebo. It reported markedly lower blood lactate and a large reduction in the time taken to complete a 2.5 km mountain march. Groups of seven to ten people cannot support a reliable estimate, and differences of that size in samples this small should be treated with caution. A separate Russian human study of short-term altitude adaptation gave bemethyl together with bromantane, so it cannot show what bemethyl does on its own. In rats taken to simulated altitude, bemethyl's performance effect disappeared entirely.

Supported by Trial 1, Trial 2

Heat tolerance (Soviet occupational experiments, mixed results)

Three Soviet-era experiments put volunteers into heated chambers, into sealed protective equipment, or into carbon monoxide, and compared a single 500 mg dose of bemitil against placebo and against other drugs. Bemitil did better than placebo, but in each of them the authors named a different drug as the most effective: phenibut in one heat experiment, phenibut combined with propranolol in the other, and bromantane in the carbon monoxide experiment. None of the reports states how many people took part, and two of them come from the same author group in the same year and appear to describe the same series of volunteers.

Supported by Trial 2

Liver regrowth after surgery in animals (not studied in people)

In animals that had part of the liver surgically removed, bemethyl sped up regrowth of liver tissue and improved bilirubin and glycogen measures, alongside two related compounds tested in the same experiment. This has never been studied in people. Recovery from liver surgery is a medical matter and is not something to take a supplement for.

Supported by Trial 2

Cognitive performance under stress

The human signal comes from the same handful of small Soviet reports: faster visual signal detection and fewer tracking errors in operators during a simulated 56-hour spaceflight, and better scores on a concentration and mental-workability test in soldiers at altitude. The spaceflight report never says how many operators took part; the altitude report used groups of seven to ten men. Both are decades old and neither has been repeated by anyone outside the former USSR.

Supported by Trial 3, Trial 1

Mechanism of action

1

Mitochondrial protein synthesis enhancement

Animal work suggests bemethyl increases the synthesis of mitochondrial and gluconeogenic enzymes, and blocking RNA and protein synthesis with actinomycin D abolishes its protective effect in animals. The review that describes this mechanism states plainly that the specific way bemethyl drives RNA and protein expression remains unknown.

2

Antihypoxant — reduced oxygen requirements under stress

Reduces cellular oxygen requirements during stress states. The class-defining actoprotector mechanism — enables performance enhancement without increased oxygen consumption.

3

Antioxidant activity

Antioxidant activity protects tissues from stress-induced oxidative damage — complements the antihypoxant effect.

4

Tissue distribution (rat data, showing no tissue build-up)

The rat study behind this is a tissue-distribution experiment. Bemitil was found in liver, brain, kidneys, spleen, heart, skeletal muscle, lungs, fat and testes; levels were highest in the liver after a single dose, and liver levels fell with repeat dosing as the drug was broken down faster. The authors' stated conclusion is that bemitil accumulates in blood but not in tissues. Whether anything accumulates in people has not been measured, and the course-based dosing pattern used in Russian practice does not rest on any human measurement.

5

Antimutagenic activity in laboratory and animal tests

Bemethyl reduced chromosome damage caused by chemical mutagens and by asbestos fibres in mice and in cultured human blood cells. This is laboratory and animal work only. It says nothing about disease risk in people and must not be read as protection against cancer.

6

Changes how other drugs behave

Soviet pharmacology described bemethyl as modifying the effects of other drugs taken alongside it. That is a reason for caution, not a reason to combine things. In rats bemethyl acts as a mixed-type inducer of liver cytochrome P450 enzymes, which is the mechanism by which a substance can lower the blood levels, and therefore the effectiveness, of other medicines a person is depending on.

Clinical trials

1
Comparison with piracetam and pyritinol in 130 patients (1988)

Aleksandrovskii YuA, Bobkov YuG, Neznamov GG, Serebriakova TV, Boiko SS. Zhurnal Nevropatologii i Psikhiatrii imeni S.S. Korsakova, 1988;88(3):109-115. Russian language; only the abstract exists in English. PMID 3381606.

130 patients under treatment for asthenic states within borderline neuropsychiatric disorders. Not healthy adults.

Bemitil was reported to act faster and more broadly on the asthenic symptom complex than piracetam or pyritinol, with a mild psychostimulating effect, and the size of that effect varied with the dosing schedule. The published abstract does not state that patients were randomised or blinded, there was no placebo group, and it gives neither a response rate nor a side-effect rate. Because the drug comparison was against two other drugs and not against no treatment, this cannot show how much of the improvement would have happened anyway.

2
Carbon monoxide plus heat in a chamber, Soviet volunteers (1991 and 1993)

Sedov AV et al. Gigiena Truda i Professional'nye Zabolevaniya 1991;(6):12-14 (PMID 1916390), and Sedov AV et al. Meditsina Truda i Promyshlennaya Ekologiya 1993;(9-10):10-11 (PMID 8087458). Russian language; only abstracts exist in English.

Volunteers exposed in a chamber to carbon monoxide at 300 mg/m3 and to heat of about 50 C. Neither report states how many people took part.

A single 500 mg dose of bemitil improved tolerance of carbon monoxide, and of carbon monoxide combined with extreme heat. In the 1993 experiment, which set bemitil against placebo, against bromantane, and against the two combined, the authors named bromantane alone and the bromantane-plus-bemitil combination as the most effective; bemitil on its own was not among them. These are chamber experiments about surviving an industrial exposure, not tests of athletic or everyday performance.

3
Urinary excretion study in six volunteers (2018)

Kwiatkowska D, Kowalczyk K, Grucza K, Szutowski M, Bulska E, Wicka M. Drug Testing and Analysis 2018;10(11-12):1682-1688. Department of Anti-Doping Research, Institute of Sport - National Research Institute, Warsaw. PMID 30346653.

Six healthy volunteers, three men and three women, aged 26 to 49.

Six volunteers took the Ukrainian bemitil product Antihot twice a day for three consecutive days while urine was collected for 30 days, so that anti-doping laboratories would know what to look for. Bemitil showed up in urine both as the parent compound and, more abundantly and over a longer window, as a glucuronide conjugate. This study measured detection. It did not measure performance and it did not measure safety. It was carried out because WADA had placed bemitil on its 2018 Monitoring Program; bemitil stayed on that program through 2021, was dropped from the 2022 program, and is not named on the 2026 Prohibited List.

Side effects and drug interactions

Common Potential side effects

Irritability and shortened or poorer sleep, and headache, are described in the published pharmacology of this drug class. Sweating and an unstable pulse are also commonly listed for it. No published study gives a rate for any of these effects, so how often they occur is not known.
Headache and flushing of the face.
Nausea, vomiting and discomfort in the stomach or liver area, worse when taken on an empty stomach. Bemethyl is a hydrobromide salt, and allergic reactions related to the bromide cannot be ruled out.
Anti-doping status: WADA listed bemitil (2-ethylsulfanyl-1H-benzimidazole) on its Monitoring Program, in and out of competition, from 2018 through 2021. It was dropped from the 2022 Monitoring Program and has not appeared on it since, and it is not named on the 2026 Prohibited List. The List and the Monitoring Program are revised every year, so any competing athlete should confirm the current position with their own anti-doping organisation before using an unapproved drug, and should also weigh that a product bought outside a regulated supply chain may not contain what the label says.
Pregnancy/lactation: avoid.
There is no controlled long-term safety study of bemethyl in humans, no published overdose data, and no registered clinical trial anywhere. Decades of clinical use in the former USSR are not a substitute: adverse events from that era and that literature were not systematically collected or published, so the absence of reported harm is not evidence of safety.
Contraindicated in low blood sugar and in anyone taking barbiturates, according to the pharmacology review of this drug class. There is no safety information for children, and no human data in pregnancy or breastfeeding.

Important Drug interactions

Barbiturates: the pharmacology review of this drug class lists barbiturate use as a contraindication for bemethyl.
Medicines cleared by the liver: in rats, bemethyl acts as a mixed-type inducer of cytochrome P450 enzymes, and enzyme induction is the standard mechanism by which one substance lowers the blood levels and the effectiveness of another. Anyone on prescription medication should treat this as a real interaction risk, not a theoretical one.
Blood-sugar-lowering medicines: the same review lists low blood sugar as a contraindication for bemethyl, so combining it with insulin or other glucose-lowering drugs has not been evaluated and should be avoided.
Other central nervous system drugs, including nootropics, stimulants and sedatives: Soviet-era reports describe bemethyl changing the effects of drugs given with it, in both directions. None of that work was controlled, and it is a reason to avoid combinations rather than a reason to build them.
Bromantane, phenibut and other actoprotectors and nootropics: the human chamber studies that tested bemethyl alongside these drugs were run to test survival of extreme heat and carbon monoxide, not everyday use, and in each of them the comparison drug did better than bemethyl on its own.
Everything in this list rests on Soviet-era pharmacology that was never repeated under modern standards. No formal drug interaction study of bemethyl has been published, so an absent warning here does not mean an interaction is absent.

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Frequently asked questions about Bemethyl (Bemitil / Metaprot)

What is bemethyl?

Bemethyl (bemitil) is a compound developed in Russia as an actoprotector, studied for endurance, recovery, and resilience to physical and mental stress. It is not approved as a drug or dietary supplement in the US.

What is bemethyl used for?

In Russian research it is used to support physical and mental performance under demanding conditions, recovery, and adaptation to stress, partly by supporting protein synthesis. Western evidence is limited.

How is bemethyl used?

In Russian practice it is taken orally at prescribed doses, sometimes in cycles. Because it is unapproved outside Russia, caution is essential.

Is bemethyl safe?

Nobody knows. There is no controlled long-term safety study in humans, no published overdose data, and no registered clinical trial. The known adverse effects are nausea and vomiting, disturbed sleep, irritability, headache and facial flushing, and the pharmacology review of this drug class lists low blood sugar and barbiturate use as contraindications. In rats it induces liver enzymes that metabolise other medicines. It is an unapproved drug in the United States and in Europe, so nothing verifies what is actually in a product sold as bemethyl. Anyone considering it should speak to a doctor first.

What is the recommended dosage of Bemethyl?

The clinically studied dose is Labelling describes 250 to 500 mg once or twice daily in courses of three to five days; no dose or schedule for athletic use has been established in any published study. Always follow the product label and check with a healthcare provider for personal advice.

Is Bemethyl safe, and does it have side effects?

For most healthy adults, Bemethyl is well tolerated at studied doses. Reported effects can include: Irritability and shortened or poorer sleep, and headache, are described in the published pharmacology of this drug class. Sweating and an unstable pulse are also commonly listed for it. It may also interact with some medications. Bemethyl is not right for everyone, so check with a healthcare provider first if you are pregnant or breastfeeding, have a medical condition, or take prescription medication.

Does Bemethyl interact with any medications?

Possible interactions include: Barbiturates: the pharmacology review of this drug class lists barbiturate use as a contraindication for bemethyl. Medicines cleared by the liver: in rats, bemethyl acts as a mixed-type inducer of cytochrome P450 enzymes, and enzyme induction is the standard mechanism by which on… If you take prescription medication, check with a pharmacist or doctor before using it.

How strong is the scientific evidence for Bemethyl?

NutraSmarts rates the evidence for Bemethyl as Preliminary (1 out of 5). It is backed by 3 clinical trials and 13 cited references summarized on this page. A higher rating reflects more, larger, and better-designed human studies.

References(13 citations)

Evidence ratings on NutraSmarts are based on the totality of human clinical research, with emphasis on randomized controlled trials, meta-analyses, and systematic reviews. The references below directly support claims made throughout this page.

  1. Oliynyk S, Oh S The pharmacology of actoprotectors: practical application for improvement of mental and physical performance Biomol Ther (Seoul). 2012;20(5):446-456. doi:10.4062/biomolther.2012.20.5.446.PubMedUsed to support: A narrative review of the actoprotector drug class by researchers at Ewha Womans University in Seoul, summarising the Soviet and post-Soviet literature on bemitil: its development history, its proposed mechanisms of protein synthesis activation, gluconeogenesis and indirect antioxidant action, and its adverse effects. The review states that bemitil's official manufacture and clinical use were discontinued after 1991, that it is now made in Ukraine under the name Antihot and certified there as a dietary supplement, and that the specific mechanism by which it drives protein expression remains unknown. It lists nausea and vomiting, stomach or liver discomfort, irritability, shortened sleep, headache and facial flushing as adverse effects, possible bromide-related allergy, and contraindications in low blood sugar and with barbiturates. It is a review of other people's work, not a trial, and most of the studies it summarises are Russian-language reports that cannot be independently checked.
  2. Boĭko SS, Bobkov IuG, Neznamov GG, Serebriakova TV Pharmacokinetics and the clinical effect of bemitil after a single administration Farmakol Toksikol. 1986;49(5):17-20..PubMedUsed to support: A 1986 Russian-language report on how a single dose of bemitil is absorbed and cleared in patients with asthenic states. Patients in whom the drug acted as a stimulant had a larger area under the concentration-time curve and a shorter half-life than those in whom it acted as a sedative, and the authors suggested using this to set the length of a treatment course. The number of patients is not given in the published abstract, there was no control group, and the study measured drug levels rather than whether the drug worked. It comes from the same author group, and appears to draw on the same patient series, as the 1988 comparison study also listed here.
  3. Makarov VI, Tiurenkov IN, Klauchek SV, Nalivaĭko IIu, Antipova AIu The enhancement of human thermal resistance by the single use of bemitil and fenibut Eksp Klin Farmakol. 1997;60(1):68-71..PubMedUsed to support: A 1997 Russian-language experiment in which people performing intensive physical work in sealed protective equipment received a single dose of either bemitil 0.5 g or phenibut 0.25 g. Both drugs raised thermal resistance, supported blood oxygenation and helped maintain working capacity under conditions that would otherwise cause overheating, and the authors state that the best protective effect came from phenibut rather than from bemitil. The number of participants is not given in the published abstract. This report shares its five authors, its year, its drugs and its doses with a companion heat-tolerance paper and is best read as part of one experimental series.
  4. Bobkov IuG, Epishkin AK [Effect of actoprotectors on the work capacity of operators during modeling of various factors of space flight] Kosm Biol Aviakosm Med. 1988;22(5):20-3. Russian language; English abstract only..PubMedUsed to support: Operators working 56 continuous hours in a simulated space flight environment performed better on bemethyl than on placebo: compensatory tracking quality was on average 10 percent higher, pursuit-tracking errors were 1.8 times lower, and visual signal detection time was 2.4 times shorter. The report does not state how many operators took part, and the work has not been replicated outside the former USSR.
  5. Aleksandrovskiĭ IuA, Bobkov IuG, Neznamov GG, Serebriakova TV, Boĭko SS [Use of the new psychotropic preparation bemitil in treating asthenic disorders (clinico-pharmacological research)] Zh Nevropatol Psikhiatr Im S S Korsakova. 1988;88(3):109-15. Russian language; English abstract only..PubMedUsed to support: In 130 patients with asthenic conditions related to borderline neuro-mental disturbances, bemitil was compared with the drugs piracetam and pyritinol and was reported to act on the asthenic symptom complex more broadly and with a faster onset, along with a mild psychostimulating effect that varied with the dosing schedule. The published abstract does not state that patients were randomised or blinded and reports no placebo group, no response rate and no adverse-event rate. This paper shares its author group and apparently its patient series with the 1986 pharmacokinetic report also listed here.
  6. Sedov AV, Lukicheva TA, Surovtsev NA, Akin'shin AV, Nazarov LIu, Miroshnik SV [Experimental rationale for the use of drugs to increase the resistance of the human body to the combined action of carbon monoxide and hyperthermia] Med Tr Prom Ekol. 1993;(9-10):10-11. Russian language; English abstract only..PubMedUsed to support: Volunteers exposed to carbon monoxide at 300 mg per cubic metre together with a heating microclimate of about 50 C received placebo, bemitil 0.5 g, bromantane 0.25 g, or bemitil plus bromantane. The authors concluded that bromantane alone, or bromantane combined with bemitil, were the most effective at increasing tolerance; bemitil on its own was not among the arms they identified as most effective. The number of volunteers is not reported.
  7. Makarov VI, Tiurenkov IN, Klauchek SV, Nalivaĭko IO, Antipova AIu [Experimental bases of the use of pharmacologic agents aimed at higher heat resistance of humans as means of individual protection] Med Tr Prom Ekol. 1997;(5):35-8. Russian language; English abstract only..PubMedUsed to support: Volunteers working in protective equipment at 30 C and 35 percent humidity received placebo, bemethyl 0.5 g, phenibut 0.25 g, propranolol 0.08 g, or phenibut combined with propranolol. The authors concluded that phenibut plus propranolol was the most effective way to raise tolerance of the combined occupational stressors. This report carries the same five authors, the same year, the same drugs and the same doses as the companion heat-tolerance paper also listed here, and the two are best read as one experimental series rather than as two independent studies.
  8. Gaĭvoronskaia VV, Okovityĭ SV, Shustov EB, Smirnov AV [Effects of bemethyl, ethomersol, and yakton on the liver regeneration after partial hepatectomy] Eksp Klin Farmakol. 2000;63(5):34-6. Russian language; English abstract only..PubMedUsed to support: In an animal partial-hepatectomy model, bemethyl, ethomersol and yakton each accelerated regrowth of liver tissue, raised nucleic acid and glycogen content, lowered blood bilirubin and improved liver morphology, outperforming a combination of riboxin and potassium orotate. This is an animal surgical model; nothing comparable has been studied in people.
  9. Sorokina EA, Sibiriak SV, Sergeeva SA [Effect of bemethyl on cytochrome P-450-dependent monoxygenases in the human liver and lymphocytes] Eksp Klin Farmakol. 2002;65(3):31-4. Russian language; English abstract only..PubMedUsed to support: Given orally to rats at 50 mg/kg, bemethyl behaved as a mixed-type inducer of cytochrome P450, raising total P450 content in liver microsomes and increasing several monooxygenase activities, with the strongest induction after a single dose. In cultured human lymphocytes, high concentrations raised one of the measured enzyme activities and low concentrations raised another. Enzyme induction of this kind is how a substance can reduce the blood levels of other medicines, so this is a drug interaction signal, although it has never been tested in people taking bemethyl.
  10. Sergeeva SA, Gulyaeva IL Distribution of bemitil in organs and tissues of rats after single or repeated administration Bull Exp Biol Med. 2006;141(5):596-8. doi:10.1007/s10517-006-0230-0.PubMedUsed to support: After single and repeated oral dosing in rats, bemitil was found in liver, brain, kidneys, spleen, heart, skeletal muscle, lungs, fat and testes. Accumulation was greatest in the liver after a single dose, but liver concentrations fell with repeat dosing as biotransformation increased. The authors' conclusion is that bemitil accumulates in blood rather than in tissues. No equivalent measurement has been made in humans.
  11. Kibal'chich DA, Belolipetskaia VG, Blagodatskikh SV, Martsevich SIu, Rudenko LI, Iatsuk VR [Pharmacokinetics of domestic actoprotector drug Metaprot in healthy volunteers] Eksp Klin Farmakol. 2011;74(6):30-2. Russian language; English abstract only..PubMedUsed to support: A single 250 mg oral capsule of Metaprot was given to a group of healthy adult volunteers; peak plasma concentration of ethylthiobenzimidazole averaged 0.91 micrograms per millilitre at about 1.1 hours, and the distribution of pharmacokinetic parameters across the group was polymodal, meaning people handled the drug quite differently from one another. The number of volunteers is not stated in the published abstract, and the study measured blood levels rather than any effect.
  12. Kundashev UK, Zurdinov AZ, Barchukov VG [Possibilities of the pharmacological correction of adaptive reactions of human organism in short-term moving from middle to high altitude] Eksp Klin Farmakol. 2014;77(9):32-7. Russian language; English abstract only..PubMedUsed to support: Volunteers moving from 1,670 m to 3,750 m received tablets or placebo before and during the ascent. The active arm that showed faster short-term adaptation, better tolerance of physical activity at altitude and quicker blood-count responses was metaprot 0.125 g combined with ladasten (bromantane) 0.1 g, compared against hypoxen 0.5 g alone and against placebo. Because bemethyl was only given together with a second drug, this study cannot show what bemethyl does on its own.
  13. Kwiatkowska D, Kowalczyk K, Grucza K, Szutowski M, Bulska E, Wicka M Detection of bemitil and its metabolite in urine by means of LC-MS/MS in view of doping control analysis Drug Test Anal. 2018;10(11-12):1682-1688. doi:10.1002/dta.2524.PubMedUsed to support: Six healthy volunteers, three men and three women aged 26 to 49, took the Ukrainian bemitil-containing product Antihot twice daily for three days while urine was collected for up to 30 days, so that anti-doping laboratories could establish detection markers. Bemitil was traceable both as the parent compound and, more abundantly and over a longer window, as its glucuronide conjugate. The paper also records that 2-(ethylthio)benzimidazole is the active ingredient of Antihot, sold in Ukraine as a dietary supplement, and that WADA included bemitil in its 2018 monitoring program. This study measured urinary detection, not performance and not safety.