Clen

Clen, short for clenbuterol, is a synthetic beta-2 adrenergic agonist developed in the 1960s. It is authorized for veterinary use in some countries as a bronchodilator for horses and other animals, but it has no approved indication for human medical use in many jurisdictions.

In humans, clenbuterol is not generally approved as a prescription drug and is often encountered only in unregulated products or illicit markets. It has been used illicitly for weight loss and performance enhancement, and its availability varies by country. The drug is banned for human use in many places and is prohibited by most major sports organizations.

Pharmacologically, clenbuterol stimulates beta-2 receptors, producing bronchodilation and promoting lipolysis and thermogenesis. It tends to have a relatively long duration of action, which can lead to prolonged effects and accumulation with repeated dosing. This pharmacology underpins both its appeal for some users and its risk profile.

Safety and adverse effects are a major concern. Common side effects include tachycardia, palpitations, tremor, anxiety, and headaches, along with electrolyte disturbances such as low potassium. With high doses or prolonged use, there is an increased risk of hypertension, arrhythmias, and potential cardiac remodeling or cardiomyopathy. The quality and purity of non-prescription clenbuterol products are often uncertain, amplifying safety risks.

Regulatory status varies widely by country but generally emphasizes caution or prohibition for human use due to health risks. In the context of athletics, clenbuterol is typically banned by anti-doping authorities.