What are possible side effects of beta blockers?

Treatment with beta blockers may be associated with a number of potential side effects. Some of the more serious side effects may be related to the degree to which beta blockers inhibit the relaxation of the bronchial passages in the lungs. This may restrict airflow in the lungs, making it difficult for patients to draw in oxygen and push out carbon dioxide. As such, beta blockers should be prescribed with care or avoided altogether in patients who are known to have underlying asthma, emphysema, or chronic obstructive pulmonary disease. Other serious side effects may be related to the degree to which beta blockers suppress the generation and conduction of electrical signals that stimulate the contraction of different chambers of the heart. This may be an important consideration in patients who have abnormal heart rhythms called bradyarrhythmias or heart blocks. If a patient with a significant bradyarrhythmia or heart block is exposed to a beta blocker, the heart rate may slow down to the point where the cardiovascular system can no longer maintain the normal flow of blood through the brain. This may lead to a sudden loss of consciousness and physical collapse identified as an episode of syncope. Patients who have diabetes mellitus who are treated with beta blockers may have problems detecting many of the warning signs associated with dangerous lowering of the blood sugar. This condition is called hypoglycemic unawareness. Beta blockers may also be associated with an higher incidence of impotence, a side effect that is common to a number of different medications used to treat hypertension.