Clenbuterol, marketed as Spiropent and Ventipulmin, is a sympathomimetic amine used by sufferers of breathing disorders as a decongestant and bronchodilator. People with chronic breathing disorders such as asthma use this as a bronchodilator to make breathing easier. It is most commonly available as the hydrochloride salt, clenbuterol hydrochloride.

Clenbuterol is a β2 agonist with some structural and pharmacological similarities to epinephrine and salbutamol, but its effects are more potent and longer-lasting as a stimulant and thermogenic drug. It causes an increase in aerobic capacity, central nervous system stimulation, and an increase in blood pressure and oxygen transportation. It increases the rate at which body fat is metabolized while increasing the body's BMR. It is commonly used for smooth muscle relaxant properties. This means that it is a bronchodilator and tocolytic.

Clenbuterol is usually used in dosages anywhere from 20-60 micrograms (mcg) a day when prescribed. A dose of about 20 mcg (women) or 40 mcg (men) should never be exceeded in a day.