Clenbuterol is a sympathomimetic beta-2 adrenergic agonist. Activation of beta-2 receptors can relax airway smooth muscle while also producing systemic effects such as increased heart rate and stimulation.

Although clenbuterol has been used therapeutically for respiratory conditions in some countries, it is not approved for human medical use in the United States. Its use outside appropriate medical settings can carry substantial cardiovascular risk.

Potential adverse effects include tremor, palpitations, anxiety, tachycardia, electrolyte disturbances, and, in severe cases, cardiac complications.