1 What is Didrex?

Brand: Didrex

Generic: Benzphetamine Hydrochloride

Brand name:


Benzphetamine Hydrochloride is a short term oral treatment for obesity as an adjunct to caloric restriction. This drug is available as a tablet containing benzphetamine hydrochloride 50 milligram.


You should read the product information leaflet before using this medication. If you have any questions, ask your doctor or pharmacist.

This medication should be taken by mouth as instructed by your doctor. Do not crush or chew the drug because it may diminish its effects. This medication should be taken with a full glass of water unless your doctor tells you otherwise. You should swallow the drug whole.

Your dosage is based on your medical condition and the way you will respond to treatment. Take this drug regularly to experience the most benefits. You should also take this drug at the same time each day.

If you miss a dose, use it as soon as you remember. Continue to use it as prescribed by your doctor or as stated on the package label.


Benzphetamine may interact with medications such as:

  • Other appetite-suppressant drugs in the past year (e.g., phentermine, sibutramine, ephedra/ma huang)
  • MAO inhibitors (isocarboxazid, linezolid, methylene blue, moclobemide, phenelzine, procarbazine, rasagiline, selegiline, tranylcypromine)
  • Drugs for depression (e.g., TCAs such as imipramine, SSRIs and SNRIs such as paroxetine, fluoxetine, venlafaxine, duloxetine)
  • Drugs for diabetes (e.g., insulin, sulfonylureas such as glipizide)
  • Drugs that affect the acid level of urine (e.g., sodium bicarbonate)
  • High blood pressure medicine (e.g., guanethidine, methyldopa)
  • Phenothiazines (e.g., prochlorperazine, promethazine, chlorpromazine)
  • Other stimulants (e.g., amphetamines, methylphenidate, street drugs such as cocaine or MDMA/"ecstasy")
  • Certain antihistamines (e.g., diphenhydramine)
  • Anti-seizure drugs (e.g., carbamazepine)
  • Medicine for sleep or anxiety (e.g., alprazolam, diazepam, zolpidem)
  • Muscle relaxants
  • Narcotic pain relievers (e.g., codeine)
  • Psychiatric medicines (e.g., risperidone, amitriptyline, trazodone)
  • Isoniazid (INH)
  • Tricyclic antidepressants (e.g., amitriptyline), among others
  • Caffeine

Side Effects

There are no side effects known aside from a possible allergic reaction in people who have previous or unknown hypersensitivity to the drug.

Watch out for signs of allergic reactions such as:

  • Rash
  • Itching
  • Swelling


Before taking this medication, tell your doctor or pharmacist if you have the following:

  • Allergy to benzphetamine or to any other sympathomimetic amines (e.g., decongestants such as pseudoephedrine, stimulants such as amphetamine, appetite suppressants such as phentermine)
  • Uncontrolled high blood pressure
  • Glaucoma
  • History of alcohol/drug abuse, vascular heart disease (e.g., chest pain, heart attack)
  • Mental/mood problems (e.g., severe anxiety, bipolar disorder, psychosis, schizophrenia)
  • High blood pressure in the lungs (pulmonary hypertension)
  • Stroke
  • Overactive thyroid (hyperthyroidism)
  • Diabetes
  • Controlled high blood pressure
  • Other heart problems (e.g., heart murmur, fast/irregular heartbeat, heart valve problems)
  • Kidney disease
  • Seizure problem
  • Pregnancy or lactation
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