Side Effects

Drug information provided by: Merative, Micromedex®

In rats and mice, phenoxybenzamine has been found to increase the risk of development of malignant tumors. It is not known if phenoxybenzamine increases the chance of tumors in humans.

Along with its needed effects, a medicine may cause some unwanted effects. Although not all of these side effects may occur, if they do occur they may need medical attention.

Some side effects may occur that usually do not need medical attention. These side effects may go away during treatment as your body adjusts to the medicine. Also, your health care professional may be able to tell you about ways to prevent or reduce some of these side effects. Check with your health care professional if any of the following side effects continue or are bothersome or if you have any questions about them:

More common

  1. Dizziness or lightheadedness, especially when getting up from a lying or sitting position
  2. fast heartbeat
  3. pinpoint pupils
  4. stuffy nose

Less common

  1. Confusion
  2. drowsiness
  3. dryness of mouth
  4. headache
  5. lack of energy
  6. sexual problems in males
  7. unusual tiredness or weakness

Other side effects not listed may also occur in some patients. If you notice any other effects, check with your healthcare professional.

Call your doctor for medical advice about side effects. You may report side effects to the FDA at 1-800-FDA-1088.

Portions of this document last updated: Feb. 01, 2024

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