Alpha blockers, also called alpha-adrenergic antagonists, treat conditions such as high blood pressure and benign prostatic hyperplasia. Find out more about this class of medication.

By Mayo Clinic Staff

Alpha blockers relax certain muscles and help small blood vessels remain open. They work by keeping the hormone norepinephrine (noradrenaline) from tightening the muscles in the walls of smaller arteries and veins, which causes the vessels to remain open and relaxed. This improves blood flow and lowers blood pressure.

Because alpha blockers also relax other muscles throughout the body, these medications can help improve urine flow in older men with prostate problems.

Several alpha blockers are available, in either short-acting or long-acting forms. Short-acting medications work quickly, but their effects last only a few hours. Long-acting medications take longer to work, but their effects last longer. Which alpha blocker is best for you depends on your health and the condition being treated.

Alpha blockers are also called alpha-adrenergic blocking agents, alpha-adrenergic antagonists, adrenergic blocking agents and alpha-blocking agents.

Examples of alpha blockers used to treat high blood pressure include:

  • Doxazosin (Cardura)
  • Prazosin (Minipress)
  • Terazosin

Doctors prescribe alpha blockers to prevent, treat or improve symptoms mainly in these conditions:

  • High blood pressure
  • Enlarged prostate (benign prostatic hyperplasia)

Though alpha blockers are commonly used to treat high blood pressure, they're typically not the first treatment option. Instead, they're used in combination with other drugs, such as diuretics, when your high blood pressure is difficult to control.

Some alpha blockers might have what's called a "first-dose effect." When you start taking an alpha blocker, you might develop pronounced low blood pressure and dizziness, which can make you faint when you rise from a sitting or lying position. As a result, the first dose is often taken at bedtime.

Other side effects might include:

  • Headache
  • Pounding heartbeat
  • Weakness
  • Dizziness
  • Weight gain

On the positive side, alpha blockers might decrease low-density lipoprotein (LDL) cholesterol (the "bad" cholesterol).

Alpha blockers can increase or decrease the effects of other medications you take. Before taking an alpha blocker, be sure your doctor knows about other medications you take, such as beta blockers, calcium channel blockers or medications for erectile dysfunction.

Some research has found that long-term use of some alpha blockers can increase the risk of heart failure. More research is needed to confirm this finding.

June 15, 2016