Selective alpha antagonists (alpha 1 blockers) include prazosin, terazosin and doxazosin. These drugs are sometimes used to treat high blood pressure, as well as benign prostatic hyperplasia (BPH), an enlargement of the prostate that may cause the urethra to constrict, inhibiting urination. They may also be used in the treatment of pheochromocytoma, a rare blood pressure-related condition.

Alpha 1 blockers decrease resistance within blood vessels and increase vein capacity, increasing the flow of blood in the heart and reducing cardiac output – a measure of the heart’s workload. They are among the only antihypertensive drugs that have been shown to lower LDL cholesterol, raise HDL cholesterol and improve the body's ability to use insulin, which reduces the risk of diabetes. Alpha 1 blockers have also been found effective in the prevention and treatment of post-traumatic stress disorder, particularly in reducing trauma-related nightmares.

However, alpha 1 blockers may also have pronounced side effects and, as shown in the ALLHAT trials, doxazosin may increase the risk of heart failure over long-term use.

Nonselective alpha antagonists (alpha 1 and alpha 2 blockers) are used in the treatment of various types of peripheral vascular disease, which include the following:

In addition, nonselective alpha antagonists are sometimes prescribed to treat migraine headaches or frostbite.

None of the forms of alpha blockers are typically used as first-line treatment for high blood pressure (hypertension). While they do lower blood pressure, alpha blockers also have relatively bothersome side effects and certain alpha blockers have been shown to increase the risk of heart failure with long-term use.  Other antihypertensive medications not only lower blood pressure, but also reduce the risk of cardiovascular disease or death and are therefore a better choice for the treatment of hypertension.