Didrex is a stimulant that is similar to an amphetamine. Benzphetamine is an appetite suppressant that affects the central nervous system.

Didrex is used together with diet and exercise to treat obesity (overweight).

Didrex may also be used for purposes not listed in this medication guide.

Didrex can harm an unborn baby or cause birth defects. Do not use this medicine if you are pregnant.

Do not use Didrex if you have used an MAO inhibitor in the past 14 days. A dangerous drug interaction could occur. MAO inhibitors include isocarboxazid, linezolid, methylene blue injection, phenelzine, rasagiline, selegiline, tranylcypromine, and others.

Taking Didrex together with other diet medications (including medicines available over the counter) can cause a rare fatal lung disorder called pulmonary hypertension. Do not take this medicine with any other diet medications without your doctor's advice.

Didrex may be habit-forming and should be used only by the person it was prescribed for. Never share this medicine with another person, especially someone with a history of drug abuse or addiction. Keep track of the amount of medicine used from each new bottle. Benzphetamine is a drug of abuse and you should be aware if anyone is using your medicine improperly or without a prescription.

Before taking this medicine

Do not use Didrex if you have used an MAO inhibitor in the past 14 days. A dangerous drug interaction could occur. MAO inhibitors include isocarboxazid, linezolid, methylene blue injection, phenelzine, rasagiline, selegiline, tranylcypromine, and others.

Taking Didrex together with other diet medications (including medicines available over the counter) can cause a rare fatal lung disorder called pulmonary hypertension. Do not take Didrex with any other diet medications without your doctor's advice.

You should not take this medicine if you are allergic to benzphetamine, or if you have:

• coronary artery disease (hardening of the arteries);

• heart disease, heart rhythm disorder;

• severe or uncontrolled high blood pressure;

• overactive thyroid;

• glaucoma;

• if you are pregnant;

• if you have a history of drug or alcohol abuse; or

• if you have used any other diet pills within the past year.

To make sure Didrex is safe for you, tell your doctor if you have:

• high blood pressure;

• diabetes; or

• a thyroid disorder.

Didrex may be habit-forming and should be used only by the person it was prescribed for. Never share Didrex with another person, especially someone with a history of drug abuse or addiction. Keep the medication in a place where others cannot get to it.

FDA pregnancy category X. This medication can harm an unborn baby or cause birth defects. Do not use Didrex if you are pregnant. Tell your doctor right away if you become pregnant during treatment. Use effective birth control while you are using this medication.

Benzphetamine can pass into breast milk and may harm a nursing baby. You should not breast-feed while taking this medicine.

Do not give this medication to a child younger than 12 years old.

Take Didrex exactly as prescribed by your doctor. Do not take in larger or smaller amounts or for longer than recommended. Follow the directions on your prescription label.

Didrex is usually taken once each day, mid-morning or mid-afternoon.

Talk with your doctor if you have increased hunger or if you otherwise think the medication is not working properly. Taking more of this medication will not make it more effective and can cause serious, life-threatening side effects.

Didrex should be taken only for a short time, such as a few weeks. Tell your doctor if you have not lost any weight after 4 weeks of treatment.

Didrex is only part of a complete program of treatment that may also include diet, exercise, and weight control. Follow your diet, medication, and exercise routines very closely.

Store at room temperature away from moisture and heat.

Keep track of the amount of medicine used from each new bottle. Benzphetamine is a drug of abuse and you should be aware if anyone is using your medicine improperly or without a prescription.

Do not use Didrex if you have used an MAO inhibitor in the past 14 days. A dangerous drug interaction could occur. MAO inhibitors include isocarboxazid, linezolid, methylene blue injection, phenelzine, rasagiline, selegiline, tranylcypromine, and others.

Taking Didrex together with other diet medications (including medicines available over the counter) can cause a rare fatal lung disorder called pulmonary hypertension. Do not take Didrex with any other diet medications without your doctor's advice.

You should not take this medicine if you are allergic to benzphetamine, or if you have:

• coronary artery disease (hardening of the arteries);

• heart disease, heart rhythm disorder;

• severe or uncontrolled high blood pressure;

• overactive thyroid;

• glaucoma;

• if you are pregnant;

• if you have a history of drug or alcohol abuse; or

• if you have used any other diet pills within the past year.

To make sure Didrex is safe for you, tell your doctor if you have:

• high blood pressure;

• diabetes; or

• a thyroid disorder.

Didrex may be habit-forming and should be used only by the person it was prescribed for. Never share Didrex with another person, especially someone with a history of drug abuse or addiction. Keep the medication in a place where others cannot get to it.

FDA pregnancy category X. This medication can harm an unborn baby or cause birth defects. Do not use Didrex if you are pregnant. Tell your doctor right away if you become pregnant during treatment. Use effective birth control while you are using this medication.

Benzphetamine can pass into breast milk and may harm a nursing baby. You should not breast-feed while taking this medicine.

Do not give this medication to a child younger than 12 years old.

Take the missed dose as soon as you remember. Skip the missed dose if it is almost time for your next scheduled dose. Do not take extra medicine to make up the missed dose.

Seek emergency medical attention or call the Poison Help line at 1-800-222-1222. An overdose of Didrex can be fatal.

Overdose symptoms may include confusion, panic, feeling hostile or aggressive, nausea, vomiting, diarrhea, stomach cramps, fever, muscle pain or weakness, dark colored urine, irregular heartbeat, weak pulse, slow breathing, feeling light-headed, seizure, or fainting.

Drinking alcohol can increase certain side effects of Didrex.

To prevent sleep problems, avoid taking this medication late in the afternoon.

Didrex may impair your thinking or reactions. Be careful if you drive or do anything that requires you to be alert.

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

Stop using Didrex 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 Didrex 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.

Tell your doctor about all medicines you use, and those you start or stop using during your treatment with Didrex, especially:

• an antidepressant--citalopram, escitalopram, desvenlafaxine, duloxetine, fluoxetine, paroxetine, sertraline, venlafaxine, vilazodone, and others; or

• a stimulant or ADHD medication such as Adderall or Ritalin.

This list is not complete. Other drugs may interact with benzphetamine, including prescription and over-the-counter medicines, vitamins, and herbal products. Not all possible interactions are listed in this medication guide.