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Didrex Side Effects

Generic Name: benzphetamine

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

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

For the Consumer

Applies to benzphetamine: oral tablet

In addition to its needed effects, some unwanted effects may be caused by benzphetamine (the active ingredient contained in Didrex). In the event that any of these side effects do occur, they may require medical attention.

You should check with your doctor immediately if any of these side effects occur when taking benzphetamine:

More common
  • Agitation
  • anxiety
  • confusion
  • convulsions (seizures)
  • dizziness
  • fast, irregular, pounding, or racing heartbeat or pulse
  • feeling lightheaded or faint
  • hallucinations
  • headache
  • hives or welts
  • irritability
  • itching
  • lightheadedness
  • mood or other mental changes
  • nervousness
  • nightmares
  • numbness or tingling in the arms or legs
  • redness of skin
  • restlessness
  • shakiness in the legs, arms, hands, or feet
  • skin rash
  • sleeplessness
  • sweating
  • trembling of the hands or feet
  • trouble with sleeping
  • trouble with thinking, speaking, or walking
  • unable to sleep
  • unusual feeling of excitement
  • weakness
  • Chest discomfort or pain
  • difficulty breathing
  • discouragement
  • feeling sad or empty
  • lack of appetite
  • loss of interest or pleasure
  • severe mental changes
  • shortness of breath
  • swelling of the feet or lower legs
  • trouble with concentrating
  • trouble with breathing
  • unusual tiredness or weakness

If any of the following symptoms of overdose occur while taking benzphetamine, get emergency help immediately:

Symptoms of overdose
  • Blurred vision
  • change in consciousness
  • dark-colored urine
  • diarrhea
  • dizziness, faintness, or lightheadedness when getting up from a lying or sitting position suddenly
  • fever
  • loss of consciousness
  • muscle cramps or spasms
  • muscle pain or stiffness
  • nausea
  • nervousness
  • physical attempt to injure oneself
  • pounding in the ears
  • rapid, shallow breathing
  • severe anxiety or feeling of panic
  • stomach cramps
  • violent actions
  • vomiting

Some of the side effects that can occur with benzphetamine 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
  • Decrease in sexual ability, desire, drive, or performance
  • decreased interest in sexual intercourse
  • dry mouth
  • inability to have or keep an erection
  • increase in sexual ability, desire, drive, or performance
  • increased interest in sexual intercourse
  • unpleasant taste

For Healthcare Professionals

Applies to benzphetamine: oral tablet


Cardiovascular side effects have included palpitation, tachycardia, and elevation of blood pressure. Isolated cases of cardiomyopathy and ischemic cardiac events have been reported in association with chronic amphetamine use. Valvular heart disease associated with the use of some anorectic agents such as fenfluramine and dexfenfluramine (both independently and especially when used in combination with other anorectic drugs) has been reported; however, no cases of this valvulopathy have been reported when benzphetamine (the active ingredient contained in Didrex) has been used alone.[Ref]

Nervous system

Nervous system side effects have included restlessness, overstimulation, insomnia, dizziness, tremor, sweating, and headache.[Ref]


Psychiatric side effects have included depression following withdrawal of the drug and, rare instances of psychotic episodes.[Ref]


Gastrointestinal side effects have included nausea, diarrhea, unpleasant taste, dry mouth, and other gastrointestinal disturbances.[Ref]


Genitourinary side effects have included changes in libido.[Ref]


Hypersensitivity side effects have included urticaria and other allergic reactions involving the skin.[Ref]


1. "Product Information. Didrex (benzphetamine)" Pharmacia and Upjohn, Kalamazoo, MI.

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