Dexfenfluramine (By mouth)


Dexfenfluramine (dex-fen-FLUR-a-meen)

Used as part of a diet plan to help you lose weight.

Brand Name(s)

There may be other brand names for this medicine.

When This Medicine Should Not Be Used

You should not use this medicine if you have had an allergic reaction to dexfenfluramine or related medicines such as fenfluramine (Pondimin®) or amphetamines.You should not use dexfenfluramine if you have pulmonary hypertension (high blood pressure in your lungs).You should not use dexfenfluramine if you have taken a medicine called a MAO inhibitor (such as Nardil®, Marplan®, or Parnate®) within the past 14 days. These 2 medicines taken together or within 14 days of each other can cause dangerously high blood pressure or other serious side effects.

How to Use This Medicine


  • Your doctor will tell you how much to take and how often.
  • Swallow the capsule whole. Do not break or chew it.
  • Take the medicine with a meal.

If a dose is missed:

  • Take the missed dose as soon as possible, unless it is almost time for your next dose.
  • Skip the missed dose if it is almost time for your next regular dose.
  • You should not use two doses at the same time.

How to Store and Dispose of This Medicine

  • Store at room temperature, away from heat, moisture, and direct light.
  • Keep all medicine out of the reach of children.

Drugs and Foods to Avoid

Ask your doctor or pharmacist before using any other medicine, including over-the-counter medicines, vitamins, and herbal products.

  • Avoid drinking alcohol while taking this medicine.
  • Make sure your doctor knows if you are taking other medicines that may make you sleepy, such as sleeping pills, tranquilizers, some cold or allergy medicines, or strong pain killers.
  • Make sure your doctor knows if you are taking medicine for diabetes, high blood pressure, or high cholesterol. When you lose weight, your doctor may need to change your dose of these medicines.
  • Dexfenfluramine taken with some medicines to treat depression (such as Prozac®, Desyrel®, Luvox®, Serzone®, Paxil®, Zoloft®, or Effexor®) or with medicine to stop migraine headaches (such as Imitrex® or DHE 45®) can cause serious side effects. Give your doctor a list of all medicines you are taking, including medicines you get without a prescription.

Warnings While Using This Medicine

  • Talk with your doctor before taking this medicine if you have glaucoma or if you are pregnant or breastfeeding.
  • A rare side effect caused by dexfenfluramine is pulmonary hypertension, or high blood pressure in the lungs. Most people will not have this problem, but if you start to have trouble breathing or easily become short of breath, have chest pain, swelling in your feet or lower legs, or dizziness call your doctor right away. This is a very serious problem.
  • Tell your doctor if you have symptoms such as a depressed mood, tiredness, nausea, vomiting, or anxiety after you stop taking the medicine.
  • If you have taken this medicine for a long time, do not suddenly stop taking it. Talk to your doctor first. You may need to take smaller and smaller doses before you completely stop taking the medicine.
  • This medicine may make you dizzy or sleepy Be careful if you are driving a car or using machinery.
  • This medicine works best if you follow a low-calorie diet and exercise regularly.
  • This medicine may cause false results in tests that check for drugs in urine. Before having your urine tested, talk to your doctor.

Possible Side Effects While Using This Medicine

Call your doctor right away if you notice any of these side effects:

  • Trouble breathing or feeling short of breath
  • Swelling in your feet or lower legs
  • Fast or irregular heartbeat
  • Dizziness
  • Chest pain
  • Severe headache

If you notice these less serious side effects, talk with your doctor:

  • Diarrhea
  • Drowsiness
  • Dry mouth
  • Nausea, vomiting

If you notice other side effects that you think are caused by this medicine, tell your doctor

Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088

Version Info

  • Last Reviewed on 06/12/2013

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