Beta blockers are a class of Beta-adrenergic blocking agents used as medication for numerous diseases, including asthma. The first generation of beta blockers had an ill reputation for inducing heavy asthma attacks in case of certain patients, but the current generation is one that certainly shows promise. It is safe for use by most asthma patients, except the most severe cases. However, it is still not completely perfect, and may still cause unintended side-effects now and then.

Most side-effects of beta blockers have something or other to do with heart-related issues. They may include abnormally slow heart rates, tendencies to become easily fatigued, heart failure and low blood pressure. If a beta blocker is prescribed along with certain cardiac selective calcium-channel blockers, consultation with a physician is strongly advised. Their use is not recommended for patients suffering from sinus bradycardia or atrioventicular blockages.

Non-selective beta blockers may cause bronchoconstriction in asthma patients, and their use is not recommended in such cases. Hypoglycemia is another side-effect that may manifest itself if β2-blockers are used. β1-blockers are considered relatively safer, but they still should not be used without a doctor's express opinion.