What is the role of alpha-adrenergic antagonists in hypertension or benign prostatic hyperplasia?

• A. They cause vasodilation and relaxation of smooth muscle in the bladder neck; examples include doxazosin.
• B. They increase heart rate by beta stimulation.
• C. They are first-line for chronic kidney disease.
• D. They inhibit ACE.

Answer: (A)

Blocking alpha-1 receptors on vascular smooth muscle and on the smooth muscle of the bladder neck and prostate leads to two beneficial effects. First, it causes vasodilation, lowering peripheral vascular resistance and blood pressure, which helps in hypertension. Second, it relaxes the smooth muscle in the bladder neck and prostate, improving urinary flow in benign prostatic hyperplasia. Doxazosin is a typical example. These drugs are not first-line for chronic kidney disease, since ACE inhibitors or ARBs are preferred for kidney protection, and they do not inhibit ACE. They can cause reflex tachycardia due to the blood pressure drop, but they do not work by stimulating beta receptors.