Chemical Formula: C12H18Cl2N2O Description Clenbuterol is a compound that belongs to a class of drugs called beta2-agonists. Drugs in this category can cause dilation of the bronchial muscles. Beta2-agonists are often used to treat asthma. In addition to being used to treat asthma, clenbuterol has become popular as a weight loss supplement. That’s because of its effect on muscle growth and fat reduction. Read on to learn more about the usage, safety, and side effects for this medication. Side effects Clenbuterol can have negative side effects when overused or misused. These can include: