Selective alpha antagonists (alpha 1 blockers) can cause one or more of the following side effects:

Nonselective alpha antagonists (which block both alpha receptors) typically cause:

• Rapid heart rate (tachycardia)
• Pounding or “galloping” heart beat (palpitations)
• Fluid retention
• Nasal (nose) and ocular (eye) congestion.
• Aggravation of respiratory infection (if one is present)

Side effects associated with both forms of alpha blockers include:

• Low blood pressure (hypotension)
• Allergic reaction
• Swelling (edema) of feet, legs or ankles
• Chest pain
• Shortness of breath (dyspnea) or wheezing
• Weight gain
• Nausea or upset stomach
• Vomiting
• Irritability, nervousness or restlessness
• Trouble sleeping
• Nightmares and vivid dreams 
• Loss of bladder control
• Painful, continuous erection or impotence
• Back or joint pain
• Blurred vision
• Runny or stuffy nose

Side effects of alpha blockers typically diminish with regular use. Because of these side effects, however, alpha blockers are generally not the first choice of medications to treat high blood pressure or other conditions.

Individuals who have been using an alpha blocker for an extended period of time may notice unpleasant or harmful effects if they discontinue the use of the medication suddenly. Patients using alpha blockers should discuss discontinuing the drug with their physician.