• Other antihypertensives (drugs that slow heart rate or lower blood pressure) such as calcium channel blockers or ACE inhibitors. Combined, these medications may lower blood pressure to unsafe levels. However, lower doses of these medications are routinely prescribed along with alpha-blockers in patients who do not respond to other therapies. Some medications even combine more than one antihypertensive into a single pill.

  • NSAIDs (nonsteroidal anti-inflammatory drugs). Mixing these medications may reduce the effectiveness of the antihypertensive. 

  • Some antiarrhythmics (medications that treat abnormal heart rhythms (arrhythmias).

  • Impotence therapy agents. Mixing alpha blockers and impotence therapy agents could result in a sudden and unsafe drop in blood pressure.

  • Some antibiotics.

  • Some anti-fungal medications.

  • Protease inhibitors or anti-viral medications used in the treatment of HIV.

  • Some antidepressants or anti-anxiety drugs.

  • Insulin and other diabetic medications.

  • Some immunodepressants.

  • Some medications used in the treatment of conditions such as heartburn, ulcers, asthma and endometriosis.

  • Grapefruit juice. Grapefruit juice interferes with the liver’s ability to rid the body of some substances. This could lead to toxic levels of alpha blockers building up in the body. While the buildup is less likely if the juice is ingested four or more hours prior to the medicine, patients taking alpha blockers may be advised to refrain from drinking grapefruit juice.

  • Over-the-counter (OTC) medications. Patients taking alpha blockers for high blood pressure (hypertension) should avoid OTC products that may increase blood pressure (vasoconstrictors), including diet pills and asthma, cold, cough, sinus or hay fever medications. People should also be careful about using eye drops that treat bloodshot eyes.