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Cln3.0
Clenbuterol Research
Mostly mechanism / observationalLimited safety
6 peer-reviewed studies
What the evidence says
Mostly mechanism / observational
Most Clenbuterol studies are mechanism or observational rather than RCTs that measure a clinical effect — keep findings provisional.
Most evidence is from mixed-quality studies published 1992–2023 with a typical study size of 113 participants.
Based on 6 studies · 113 total participants
Confidence
Low
By outcome
Muscle / lean mass (animal)
Mostly mechanism / observational4 studies
Cardiac toxicity
Mostly mechanism / observational4 studies
Safety profile
Mostly mechanism / observational4 studies
Fat loss & repartitioning (animal)
Mostly mechanism / observational3 studies
Steady research
1 study in the last 5 years
199220072023
1Systematic Review2023
Major adverse events experienced by athletes were supraventricular tachycardia, atrial fibrillation, hypotension, chest pain, myocardial injury, myocarditis, myocardial ischemia, myocardial infarction, cardiomyopathy ... and death. ... Lack of evidence regarding the performance-enhancing effects of clenbuterol combined with its serious toxicities questions the usefulness of this drug in athletes.
Kumari S, Pal B, Sahu SK, Prabhakar PK, Tewari D · International journal of legal medicine (2023)
Top-of-pyramid synthesis and mandatory counter-evidence — a PRISMA systematic review of 23 case reports/series covering 24 athletes who experienced clenbuterol adverse events
Cardiac complications were the most common serious harm: supraventricular tachycardia, atrial fibrillation, myocardial injury, myocardial infarction, cardiomyopathy — with deaths reported
Oral ingestion was the most common route; doses ranged from 20 mcg to 30 mg, all unvalidated
Serum potassium nadir was 2.5 mEq/L ... initial lactate was 9.4 mmol/L ... Three patients underwent cardiac catheterization and none had significant coronary artery disease. Clenbuterol was detected in all patients after comprehensive testing.
Hieger MA, Emswiler MP, Maskell KF, Sentz JT, Miller KB, Wolf CE, Cumpston KL, Wills BK · The Journal of emergency medicine (2016)
A cluster of hospitalized patients with laboratory-confirmed clenbuterol exposure from adulterated heroin — the clearest human toxicity anchor
Presenting with chest pain, dyspnea, palpitations; median heart rate 120 beats/min, severe hypokalemia (K+ nadir 2.5 mEq/L), elevated lactate, and troponin elevation
Myocardial injury occurred despite clean coronary arteries on catheterization — direct beta-2-mediated cardiac toxicity, not atherosclerotic
In an investigation of 113 cases of clenbuterol poisoning in Catalonia, Spain, in 1992, more than 50 percent of those affected were found to have had symptoms of nervousness, tachycardia, muscle tremors, myalgia, and headache.
Salleras L, Domínguez A, Mata E, Taberner JL, Moro I, Salvà P · Public health reports (1995)
A 113-case food-poisoning outbreak from clenbuterol-tainted veal liver — documents the population-level harm of illicit clenbuterol in the food chain
Over half of those affected had nervousness, tachycardia, muscle tremors, myalgia, and headache; symptoms lasted up to 6 days
Clenbuterol detected in 47 urine samples (11–486 ppb); the liver–illness association was highly significant (P < 0.0001)
Clenbuterol, presented to rats in the diet (4 mg/kg), caused significant increases in gastrocnemius muscle mass, protein, and RNA content and a decrease in epididymal fat pad mass ... the anabolic effects of clenbuterol are dependent on interaction with the beta 2-adrenoceptor.
Choo JJ, Horan MA, Little RA, Rothwell NJ · The American journal of physiology (1992)
Foundational mechanism / repartitioning study — in rats, dietary clenbuterol increased muscle mass, protein, and RNA while decreasing fat-pad mass
The selective beta-2 antagonist ICI-118,551 reversed the anabolic effect, establishing that the repartitioning effect is beta-2-adrenoceptor-mediated
A long duration of action was required, consistent with clenbuterol's long half-life versus shorter beta-2 agonists like salbutamol
Clenbuterol indeed largely prevented skeletal muscle waste in AH-130-bearing rats by restoring protein degradative rates close to control values ... through a decrease of the hyperactivation of the ATP-ubiquitin-dependent proteolytic pathway.
Costelli P, García-Martínez C, Llovera M, Carbó N, López-Soriano FJ, Agell N, Tessitore L, Baccino FM, Argilés JM · The Journal of clinical investigation (1995)
Outcome anchor for the anti-catabolic claim — in a cancer-cachexia rat model, clenbuterol largely prevented skeletal-muscle protein wasting
Worked by suppressing the hyperactivated ATP-ubiquitin-dependent proteolytic pathway, restoring protein-degradation rates toward normal
Showed muscle-specific action without measurable effects on parenchymal organs or on corticosterone/insulin — a clean repartitioning mechanism
The hypertrophy was more pronounced for hindlimb skeletal muscle (21% to 35% for GPS), and the effects of this relatively high dose of clenbuterol on the heart were less marked (18% to 20% hypertrophy).