Phentermine (By mouth)
Used with a diet plan for weight loss.
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 phentermine or to similar medicines such as adrenaline, amphetamine, dopamine, dobutamine, ephedrine, or lisdexamfetamine. Do not use this medicine if you are pregnant or breastfeeding. Do not use this medicine if you are normally nervous and tense or if you have glaucoma, an overactive thyroid, heart or blood vessel disease, heart rhythm problems, high blood pressure, or a history of drug abuse or strokes. You should not use this medicine if you also take an MAO inhibitor (MAOI), such as isocarboxazid, phenelzine, selegiline, tranylcypromine, Eldepryl®, Marplan®, Nardil®, or Parnate®, or if you have taken an MAOI within the past 14 days.
How to Use This Medicine
Dissolving Tablet, Capsule, Long Acting Capsule, Tablet, Dissolving Tablet
- Your doctor will tell you how much of this medicine to use and how often. Do not use more medicine or use it more often than your doctor tells you to.
- This medicine is not for long-term use.
- Take the tablet before breakfast or 1 to 2 hours after breakfast. Take the capsule 2 hours after breakfast. Take the extended-release capsule before breakfast. Take the disintegrating tablet in the morning, with or without food. To avoid trouble sleeping, always take the dose in the morning and never at bedtime or late in the evening.
- 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. Do not open the blister pack that contains the tablet until you are ready to take it. Remove the tablet from the blister pack by peeling back the foil, then taking the tablet out. Do not push the tablet through the foil. Place the tablet in your mouth. 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.
- Use only the brand of this medicine that your doctor prescribed. Different brands may not work the same way.
If a dose is missed:
- If you miss a dose or forget to use your medicine, use it as soon as you can. If it is almost time for your next dose, wait until then to use the medicine and skip the missed dose. Do not use 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 away from children and 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®, or Desoxyn®) or other diet pills. Tell your doctor if you use insulin or diabetes medicine that you take by mouth (such as glipizide, glyburide, metformin, Actos®, or Glucotrol®) or medicines for depression (such as fluoxetine, fluvoxamine, paroxetine, sertraline, Luvox®, Paxil®, Prozac®, or Zoloft®).
- Do not drink alcohol while you are using this medicine.
Warnings While Using This Medicine
- Using this medicine while you are pregnant can harm your unborn baby. Use an effective form of birth control to keep from getting pregnant. If you think you have become pregnant while using the medicine, tell your doctor right away.
- Make sure your doctor knows if you have kidney disease, heart disease, high blood pressure, diabetes, nervousness, or a history of alcohol abuse.
- Stop using this medicine and check with your doctor right away if you develop chest pain, fainting, shortness of breath, troubled breathing, or swelling of the lower legs, ankles, or feet. These may be symptoms of a serious lung disease.
- This medicine may be habit-forming. If you feel that the medicine is not working as well, do not use more than your prescribed dose. Call your doctor for instructions.
- Do not stop using this medicine suddenly without asking your doctor. You may need to slowly decrease your dose before stopping it completely.
- This medicine may make you dizzy or drowsy. Do not drive, use machines, or do anything else that could be dangerous if you are not alert.
- This medicine may affect blood sugar levels. Diabetic patients may notice a change in blood or urine sugar tests. 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
- Unusual tiredness or weakness
If you notice these less serious side effects, talk with your doctor:
- Bad taste in the mouth
- Blurred vision
- Changes in sex drive
- Confusion, restlessness, nervousness, or unusual behavior
- Dry mouth
- Headache, dizziness, or drowsiness
- Increased sweating
- Nausea, vomiting, diarrhea, constipation, or stomach cramps
- 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
- Last Reviewed on 06/12/2013
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This page was last updated: June 18, 2013