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Dibenzyline Side Effects

Generic Name: phenoxybenzamine

Note: This page contains information about the side effects of phenoxybenzamine. Some of the dosage forms included on this document may not apply to the brand name Dibenzyline.

For the Consumer

Applies to phenoxybenzamine: oral capsule

In rats and mice, phenoxybenzamine (the active ingredient contained in Dibenzyline) 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.

In addition to its needed effects, some unwanted effects may be caused by phenoxybenzamine. In the event that any of these side effects do occur, they may require medical attention.

Minor Side Effects

Some of the side effects that can occur with phenoxybenzamine may not need medical attention. As your body adjusts to the medicine during treatment these side effects may go away. Your health care professional may also be able to tell you about ways to reduce or prevent some of these side effects. If any of the following side effects continue, are bothersome or if you have any questions about them, check with your health care professional:

More common:
  • Dizziness or lightheadedness, especially when getting up from a lying or sitting position
  • fast heartbeat
  • pinpoint pupils
  • stuffy nose
Less common:
  • Confusion
  • drowsiness
  • dryness of mouth
  • headache
  • lack of energy
  • sexual problems in males
  • unusual tiredness or weakness

For Healthcare Professionals

Applies to phenoxybenzamine: compounding powder, oral capsule


Cardiovascular side effects have included postural hypotension and tachycardia. These symptoms are evidence of adrenergic blockade and vary according to the degree of blockade.[Ref]


Genitourinary side effects have included inhibition of ejaculation. This symptom is indicative of adrenergic blockade and varies according to the degree of blockade.[Ref]


Respiratory side effects have included nasal congestion. This symptom is indicative of adrenergic blockade and varies according to the degree of blockade.[Ref]


Ocular side effects have included miosis. This symptom is indicative of adrenergic blockade and varies according to the degree of blockade.[Ref]

Nervous system

Nervous system side effects have included drowsiness and fatigue.[Ref]


Gastrointestinal side effects have included gastrointestinal irritation.[Ref]


1. "Product Information. Dibenzyline Capsules (phenoxybenzamine)." SmithKline Beecham, Philadelphia, PA.

Not all side effects for Dibenzyline may be reported. You should always consult a doctor or healthcare professional for medical advice. Side effects can be reported to the FDA here.

Disclaimer: Every effort has been made to ensure that the information provided is accurate, up-to-date and complete, but no guarantee is made to that effect. In addition, the drug information contained herein may be time sensitive and should not be utilized as a reference resource beyond the date hereof. This material does not endorse drugs, diagnose patients, or recommend therapy. This information is a reference resource designed as supplement to, and not a substitute for, the expertise, skill , knowledge, and judgement of healthcare practitioners in patient care. The absence of a warning for a given drug or combination thereof in no way should be construed to indicate safety, effectiveness, or appropriateness for any given patient. does not assume any responsibility for any aspect of healthcare administered with the aid of materials provided. The information contained herein is not intended to cover all possible uses, directions, precautions, warnings, drug interactions, allergic reactions, or adverse effects. If you have questions about the substances you are taking, check with your doctor, nurse, or pharmacist.