What is phentermine?

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

Phentermine is used togther with diet and exercise to treat obesity (overweight) in people with risk factors such as high blood pressure, high cholesterol, or diabetes.

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

Precautions

Do not take phentermine if you have used an MAO inhibitor such as isocarboxazid (Marplan), phenelzine (Nardil), rasagiline (Azilect), selegiline (Eldepryl, Emsam), or tranylcypromine (Parnate) within the past 14 days. Serious, life-threatening side effects can occur if you take phentermine before the MAO inhibitor has cleared from your body.

Taking phentermine together with other diet medications such as fenfluramine (Phen-Fen) or dexfenfluramine (Redux) can cause a rare fatal lung disorder called pulmonary hypertension. Do not take phentermine with any other diet medications without your doctor's advice.

Do not take this medication if you are allergic to phentermine or other stimulants, or if you have:

  • heart disease or high blood pressure;
  • arteriosclerosis (hardening of the arteries);
  • an overactive thyroid;
  • glaucoma;
  • if you are in an agitated state; or
  • if you have a history of drug or alcohol abuse.

Before taking phentermine, tell your doctor if you are allergic to any drugs, or if you have:

  • a thyroid disorder;
  • anxiety disorder;
  • diabetes; or
  • epilepsy or another seizure disorder.

If you have any of these conditions, you may need a dose adjustment or special tests during treatment.

It is not known whether phentermine will harm an unborn baby. Do not take phentermine without telling your doctor if you are pregnant.

It is also not known whether phentermine passes into breast milk or if it could harm a nursing baby. Do not take phentermine without telling your doctor if you are breast-feeding a baby.

Do not give this medication to anyone younger than 16 years old without the advice of a doctor.

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

Avoid drinking alcohol. It can increase some of the side effects of phentermine.

Phentermine can cause side effects that may impair your thinking or reactions. Be careful if you drive or do anything that requires you to be awake and alert.

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Instructions

Seek emergency medical attention if you think you have used too much of this medication. An overdose of phentermine can be fatal.

Overdose symptoms may include confusion, hallucinations, feeling restless or aggressive, nausea, vomiting, diarrhea, stomach pain, irregular heartbeat, tremors, rapid breathing, confusion, hallucinations, feeling light-headed, fainting, or seizure (convulsions).

Take the missed dose as soon as you remember. If it is almost time for your next dose, skip the missed dose and take the medicine at your next regularly scheduled time. Do not take extra medicine to make up the missed dose.

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Side Effects

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

Stop using phentermine and call your doctor at once if you have any of these serious side effects:

  • feeling short of breath, even with mild exertion;
  • swelling, rapid weight gain;
  • chest pain, fast or uneven heartbeat, feeling like you might pass out;
  • unusual thoughts or behavior, feeling restless or confused; or
  • dangerously high blood pressure (severe headache, blurred vision, buzzing in your ears, anxiety, confusion, chest pain, shortness of breath, uneven heartbeats, seizure).

Less serious side effects may include:

  • feeling nervous or anxious;
  • headache, dizziness, tremors;
  • trouble sleeping (insomnia);
  • dry mouth or an unpleasant taste in your mouth;
  • diarrhea or constipation; or
  • itching.

This is not a complete list of side effects and others may occur. Tell your doctor about any unusual or bothersome side effect. You may report side effects to FDA at 1-800-FDA-1088.

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Interactions

Before taking phentermine, tell your doctor if you are using any of the following drugs:

  • medicines to treat high blood pressure;
  • insulin or diabetes medication you take by mouth;
  • guanadrel (Hylorel), guanethidine (Ismelin);
  • antidepressants such as citalopram (Celexa), escitalopram (Lexapro), fluoxetine (Prozac, Sarafem), fluvoxamine (Luvox), paroxetine (Paxil), or sertraline (Zoloft); or
  • antidepressants such as amitriptyline (Elavil, Etrafon), amoxapine (Ascendin), clomipramine (Anafranil), desipramine (Norpramin), doxepin (Sinequan), imipramine (Janimine, Tofranil), nortriptyline (Pamelor), protriptyline (Vivactil), or trimipramine (Surmontil).

This list is not complete and there may be other drugs that can interact with phentermine. Tell your doctor about all the prescription and over-the-counter medications you use. This includes vitamins, minerals, herbal products, and drugs prescribed by other doctors. Do not start using a new medication without telling your doctor.

Other Names

Adipex-P, Fastin, Ionamin, Obephen, Oby-Cap, Oby-Trim, Panshape M, Phentride, Pro-Fast HS, Pro-Fast SA, T-Diet, Teramine ER, Zantryl, phentermine, Phentercot, Pro-Fast SR, and Teramine

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Disclaimer

Every effort has been made to ensure that the information provided by Cerner Multum, Inc. ('Multum') is accurate, up-to-date, and complete, but no guarantee is made to that effect. Drug information contained herein may be time sensitive. Multum information has been compiled for use by healthcare practitioners and consumers in the United States and therefore Multum does not warrant that uses outside of the United States are appropriate, unless specifically indicated otherwise. Multum's drug information does not endorse drugs, diagnose patients or recommend therapy. Multum's drug information is an informational resource designed to assist licensed healthcare practitioners in caring for their patients and/or to serve consumers viewing this service as a supplement to, and not a substitute for, the expertise, skill, knowledge and judgment of healthcare practitioners. The absence of a warning for a given drug or drug combination in no way should be construed to indicate that the drug or drug combination is safe, effective or appropriate for any given patient. Multum does not assume any responsibility for any aspect of healthcare administered with the aid of information Multum provides. The information contained herein is not intended to cover all possible uses, directions, precautions, warnings, drug interactions, allergic reactions, or adverse effects. If you have questions about the drugs you are taking, check with your doctor, nurse or pharmacist.

Copyright 1996-2004 Cerner Multum, Inc. Version 2.05. Revision date 8/23/04

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