Last updated on RxList: 4/21/2020
Didrex Side Effects Center

What Is Didrex?

Didrex (benzphetamine) is a sympathomimetic amine, similar to an amphetamine, used as a short-term supplement to diet and exercise in the treatment of obesity. Didrex is available in generic form.

What Are Side Effects of Didrex?

Common side effects of Didrex include:

  • dizziness,
  • dry mouth,
  • difficulty sleeping (insomnia),
  • irritability,
  • nausea,
  • vomiting,
  • upset stomach,
  • diarrhea,
  • constipation,
  • restlessness,
  • hyperactivity,
  • headache,
  • tremors,
  • increased sweating,
  • dry mouth,
  • unpleasant taste in your mouth, or
  • skin rash.

Tell your doctor if you have unlikely but serious side effects of Didrex including:

  • fast/irregular/pounding heartbeat,
  • mental/mood changes (e.g., agitation, uncontrolled anger, hallucinations, nervousness),
  • uncontrolled muscle movements, or
  • changes in sexual ability or interest.

Dosage for Didrex

The suggested dosage of Didrex ranges from 25 to 50 mg one to three times daily. Dosage of Didrex should be individualized according to the response of the patient.

What Drugs, Substances, or Supplements Interact with Didrex?

Didrex may interact with ammonium chloride, ascorbic acid (vitamin C), K-Phos, blood pressure medications, insulin or oral diabetes medications, sodium bicarbonate, potassium citrate, sodium citrate and citric acid, sodium citrate and potassium, stimulants or ADHD medications, or antidepressants. Tell your doctor all medications and supplements you use.

Didrex During Pregnancy and Breastfeeding

Do not use Didrex if you are pregnant; it can harm a fetus or cause birth defects. Tell your doctor right away if you become pregnant during treatment with Didrex. Use birth control while you are using Didrex. Didrex can pass into breast milk and may harm a nursing baby. Breastfeeding while taking Didrex is not recommended.

Additional Information

Our Didrex (benzphetamine) Side Effects Drug Center provides a comprehensive view of available drug information on the potential side effects when taking this medication.

This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.


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Didrex Consumer Information

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Get emergency medical help if you have any of these signs of an allergic reaction: hives; difficulty breathing; swelling of your face, lips, tongue, or throat.

Stop using benzphetamine and call your doctor at once if you have:

  • shortness of breath (even with mild exertion), swelling, rapid weight gain;
  • chest pain, feeling like you might pass out;
  • pounding heartbeats or fluttering in your chest;
  • confusion or irritability, unusual thoughts or behavior; or
  • dangerously high blood pressure (severe headache, blurred vision, buzzing in your ears, anxiety, confusion, chest pain, shortness of breath, uneven heartbeats, seizure).

Common side effects may include:

  • feeling restless or hyperactive;
  • headache, dizziness, tremors;
  • sleep problems (insomnia);
  • increased sweating;
  • dry mouth or an unpleasant taste in your mouth;
  • nausea, diarrhea upset stomach; or
  • skin rash.

This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.

Read the entire detailed patient monograph for Didrex (Benzphetamine)


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Didrex Professional Information


The following have been associated with the use of benzphetamine hydrochloride:


Palpitation, tachycardia, elevation of blood pressure.

There have been isolated reports of cardiomyopathy and ischemic cardiac events associated 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, have been reported. However, no cases of this valvulopathy have been reported when DIDREX Tablets have been used alone.


Overstimulation, restlessness, dizziness, insomnia, tremor, sweating, headache; rarely, psychotic episodes at recommended doses; depression following withdrawal of the drug.


Dryness of the mouth, unpleasant taste, nausea, diarrhea, other gastrointestinal disturbances.


Urticaria and other allergic reactions involving the skin.


Changes in libido.

Read the entire FDA prescribing information for Didrex (Benzphetamine)

© Didrex Patient Information is supplied by Cerner Multum, Inc. and Didrex Consumer information is supplied by First Databank, Inc., used under license and subject to their respective copyrights.

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