Phentermine (By mouth)


Phentermine (FEN-ter-meen)

Used with a diet plan for weight loss.

Brand Name(s)

Adipex-P, Phentercot

When This Medicine Should Not Be Used

How to Use This Medicine

Dissolving Tablet, Capsule, Long Acting Capsule, Tablet, Dissolving Tablet

  • Take your medicine as directed.
  • This medicine is not for long-term use.
  • To avoid trouble sleeping, always take this medicine in the morning and never at bedtime or late in the evening.
    • Take the tablet before breakfast or 1 to 2 hours after breakfast.
    • Take the disintegrating tablet in the morning, with or without food.
    • Take the capsule 2 hours after breakfast.
    • Take the extended-release capsule before breakfast.
  • Swallow the extended-release capsule whole. Do not crush, break, or chew it.
  • If you are using the disintegrating tablet, make sure your hands are dry before you handle the tablet. Place the tablet on your tongue. It should melt quickly. After the tablet has melted, swallow or take a drink of water.
  • Carefully follow your doctor's instructions about any special diet.

If a dose is missed:

  • Take a dose as soon as you remember. If it is almost time for your next dose, wait until then and take a regular dose. Do not take extra medicine to make up for a missed dose.

How to Store and Dispose of This Medicine

  • Store the medicine in a closed container at room temperature, away from heat, moisture, and direct light.
  • Ask your pharmacist, doctor, or health caregiver about the best way to dispose of any outdated medicine or medicine no longer needed.
  • Keep all medicine out of the reach of children. Never share your medicine with anyone.

Drugs and Foods to Avoid

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

  • Make sure your doctor knows if you also use amphetamines (such as dextroamphetamine, methamphetamine, Dexedrine®, Desoxyn®) or other diet pills. Tell your doctor if you use insulin or diabetes medicine that you take by mouth (such as glimepiride, glipizide, glyburide, metformin, Actos®, Actoplus Met®, Janumet®, Januvia®, Prandin®) or medicine for depression (such as fluoxetine, fluvoxamine, paroxetine, sertraline, Luvox®, Paxil®, Prozac®, Zoloft®).
  • Do not drink alcohol while you are using this medicine.

Warnings While Using This Medicine

  • It is not safe to take this medicine during pregnancy. It could harm an unborn baby. Tell your doctor right away if you become pregnant.
  • Make sure your doctor knows if you have kidney disease, diabetes, heart disease, or high blood pressure. Tell your doctor if you are allergic to tartrazine or aspirin.
  • Check with your doctor right away if you develop shortness of breath, chest pain, fainting, or swelling of the lower legs, ankles, or feet. These may be symptoms of a serious lung disease.
  • This medicine can be habit-forming. Do not use more than your prescribed dose. Call your doctor if you think your medicine is not working.
  • Do not stop using this medicine suddenly. Your doctor will need to slowly decrease your dose before you stop it completely.
  • This medicine may make you dizzy or drowsy. Do not drive, use machines, or do anything else that could be dangerous until you know how this medicine affects you.
  • This medicine may affect blood sugar levels in patients with diabetes. Check with your doctor if you have any questions.

Possible Side Effects While Using This Medicine

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

  • Allergic reaction: Itching or hives, swelling in your face or hands, swelling or tingling in your mouth or throat, chest tightness, trouble breathing
  • Fast, slow, pounding, or uneven heartbeat
  • Seizures or tremors
  • Severe headache
  • Shortness of breath
  • Swelling of your feet or lower legs

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

  • Changes in sex drive
  • Dizziness, drowsiness, mild headache
  • Dry mouth or a bad taste in your mouth
  • Nausea, vomiting, diarrhea, constipation, stomach cramps
  • Restlessness or nervousness
  • Trouble sleeping

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 8/4/2014

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