Adverse events of clenbuterol among athletes: a systematic review of case reports and case series

Clenbuterol is a potent beta-2 agonist widely misused by professional athletes and bodybuilders. Information on clenbuterol associated adverse events is present in case reports and case series, though it may not be readily available. This systematic review aimed to critically evaluate the evidence of adverse events associated with clenbuterol among athletes. The search strategy was in accordance with PRISMA guidelines. Databases such as PubMed, Science Direct, Scopus, and Google Scholar were searched from 1990 to October 2021 to find out the relevant case reports and case series. There were 23 included studies. Using a suitable scale, the included studies’ methodological quality analysis was evaluated. In total, 24 athletes experienced adverse events. Oral ingestion of clenbuterol was the most preferred route among them. The daily administered dose of clenbuterol was ranging from 20 µg to 30 mg. Major adverse events experienced by athletes were supraventricular tachycardia, atrial fibrillation, hypotension, chest pain, myocardial injury, myocarditis, myocardial ischemia, myocardial infarction, cardiomyopathy, hepatomegaly, hyperglycemia, and death. The cardiac-related complications were the most commonly occurring adverse events. Clenbuterol is notorious to produce life-threatening adverse events including death. Lack of evidence regarding the performance-enhancing effects of clenbuterol combined with its serious toxicities questions the usefulness of this drug in athletes.