Skip to main content


Generic name: phendimetrazinefen-di-MEH-tra-zeen ]
Drug classes: Anorexiants, CNS stimulants

Medically reviewed by on Jul 18, 2022. Written by Cerner Multum.

What is Melfiat?

Melfiat is similar to an amphetamine. This medicine stimulates the central nervous system (nerves and brain), which increases your heart rate and blood pressure and decreases your appetite.

Melfiat is used together with diet and exercise to treat obesity.

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


You should not use Melfiat if you have glaucoma, overactive thyroid, severe heart problems, uncontrolled high blood pressure, advanced coronary artery disease, extreme agitation, or a history of drug abuse.

Do not use this medicine if you have used an MAO inhibitor in the past 14 days, such as isocarboxazid, linezolid, methylene blue injection, phenelzine, rasagiline, selegiline, or tranylcypromine.

Before taking this medicine

You should not use Melfiat if you are allergic to it, or if you have:

  • severe heart problems;

  • advanced coronary artery disease (clogged arteries);

  • severe or uncontrolled high blood pressure;

  • overactive thyroid;

  • glaucoma;

  • extreme agitation or nervousness; or

  • a history of drug abuse.

Do not use Melfiat 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.

Weight loss during pregnancy can harm an unborn baby, even if you are overweight. Do not use Melfiat if you are pregnant. Tell your doctor right away if you become pregnant during treatment.

Tell your doctor if you have ever had:

  • heart disease or coronary artery disease;

  • high blood pressure;

  • diabetes (your diabetes medication dose may need to be adjusted); or

  • an allergy to food dye or aspirin.

Melfiat is not approved for use by anyone younger than 12 years old.

It may not be safe to breast-feed while using this medicine. Ask your doctor about any risk.

How should I take Melfiat?

Follow all directions on your prescription label and read all medication guides or instruction sheets. Your doctor may occasionally change your dose. Use the medicine exactly as directed.

Melfiat is usually taken 1 hour before meals. Follow your doctor's dosing instructions very carefully.

Never use Melfiat in larger amounts, or for longer than prescribed. Taking more of this medication will not make it more effective and can cause serious, life-threatening side effects.

Melfiat is for short-term use only. The effects of appetite suppression may wear off after a few weeks.

Melfiat may be habit-forming. Misuse can cause addiction, overdose, or death. Selling or giving away Melfiat is against the law.

Call your doctor at once if you think this medicine is not working as well, or if you have not lost at least 4 pounds within 4 weeks.

Do not stop using Melfiat suddenly, or you could have unpleasant withdrawal symptoms. Ask your doctor how to safely stop using this medicine.

Store at room temperature away from moisture and heat. Keep the bottle tightly closed when not in use.

What happens if I miss a dose?

Use the medicine as soon as you can, but skip the missed dose if it is late in the day. Do not use two doses at one time.

What happens if I overdose?

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

Overdose symptoms may include confusion, panic, hallucinations, extreme restlessness, nausea, vomiting, diarrhea, stomach cramps, feeling tired or depressed, irregular heartbeats, weak pulse, seizure, or slow breathing (breathing may stop).

What should I avoid while taking phendimetrazine?

Avoid driving or hazardous activity until you know how Melfiat will affect you. Your reactions could be impaired.

Drinking alcohol with this medicine can cause side effects.

Melfiat side effects

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

Melfiat may cause serious side effects. Call your doctor at once if you have:

  • pounding heartbeats or fluttering in your chest;

  • tremors, severe agitation, feeling restless, trouble sleeping;

  • unusual changes in mood or behavior;

  • little or no urination; or

  • increased blood pressure--severe headache, blurred vision, pounding in your neck or ears, anxiety, nosebleed.

Common side effects of Melfiat may include:

  • flushing (warmth, redness, or tingly feeling);

  • increased sweating or urination;

  • dizziness, headache;

  • blurred vision;

  • dry mouth, nausea;

  • diarrhea, constipation, stomach pain; or

  • increased or decreased interest in sex.

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.

What other drugs will affect Melfiat?

Other drugs may affect Melfiat, including prescription and over-the-counter medicines, vitamins, and herbal products. Tell your doctor about all your current medicines and any medicine you start or stop using.

Further information

Remember, keep this and all other medicines out of the reach of children, never share your medicines with others, and use this medication only for the indication prescribed.

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.