Phentermine/topiramate (By mouth)


Phentermine Hydrochloride (FEN-ter-meen hye-droe-KLOR-ide), Topiramate (toe-PIR-a-mate)

Used in combination with diet and exercise to help you reach and maintain a healthy weight.

Brand Name(s)


There may be other brand names for this medicine.

When This Medicine Should Not Be Used

Do not use this medicine if you have had an allergic reaction to phentermine or topiramate, or if you are pregnant. Do not use this medicine if you have glaucoma or an overactive thyroid. Do not use this medicine if you have used an MAO inhibitor (MAOI) such as Eldepryl®, Marplan®, Nardil®, or Parnate® within the past 14 days.

How to Use This Medicine

Long Acting Capsule

  • Your doctor will tell you how much of this medicine to use and how often. Your dose may need to be changed several times in order to find out what works best for you. Do not use more medicine or use it more often than your doctor tells you to.
  • Take this medicine in the morning, unless your doctor tells you otherwise. It might keep you awake if you take it at night.
  • Swallow the extended-release capsule whole. Do not crush, break, or chew it.
  • Carefully follow your doctor's instructions about diet and exercise.
  • Drink extra fluids so you will pass more urine while you are using this medicine. This will keep your kidneys working well and help prevent kidney problems.
  • Your doctor should check your weight loss after 12 weeks and 24 weeks of treatment. Your doctor may tell you to stop taking this medicine or to change your dose if you have not lost enough weight. Most people should lose at least 5% of their starting weight.
  • This medicine should come with a Medication Guide. Read and follow these instructions carefully. Ask your doctor or pharmacist if you have any questions. Ask your pharmacist for the Medication Guide if you do not have one.

If a dose is missed:

  • If you miss a dose or forget to take your medicine, skip the missed dose. Take your regular dose as planned the next morning. Do no take extra medicine to make up for the 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  • Ask your pharmacist, doctor, or health caregiver about the best way to dispose of any outdated medicine or medicine no longer needed.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 are also using acetazolamide (Diamox®), dichlorphenamide (Daranide®), methazolamide (Neptazane®), zonisamide (Zonegram®), a diuretic (water pill, such as furosemide, hydrochlorothiazide, Lasix®), or medicine to treat seizures (especially valproic acid, carbamazepine, phenytoin, Depakene®, Depakote®). Tell your doctor about all other diet pills that you take.
  • Make sure your doctor knows if you also use birth control pills, insulin or diabetes medicine (such as glimepiride, glyburide, metformin, Actos®, Janumet®, Januvia®), or blood pressure medicine (such as amlodipine, atenolol, clonidine, hydrochlorothiazide (HCTZ), lisinopril, metoprolol, Benicar®, Cozaar®, Diovan®).
  • Tell your doctor if you are using any medicines that make you sleepy. These include sleeping pills, cold and allergy medicine, narcotic pain relievers, and sedatives.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.You should have a negative pregnancy test before you start taking this medicine. You should also have a pregnancy test every month during your treatment. If you miss a period while you are using this medicine, tell your doctor right away.
  • Make sure your doctor knows if you are breastfeeding, or if you have kidney disease, liver disease, heart or blood vessel disease, lung disease or breathing problems, diabetes, low blood potassium, or seizures. Tell your doctor if you eat a ketogenic diet (high in fats, low in carbohydrates and protein).
  • Rarely, this medicine may increase the risk of suicidal thoughts or actions. Tell your caregiver right away if you think about death, dying, or hurting yourself, or if you have any other unusual thoughts, feelings, or actions. Make sure your doctor knows if you have a history of suicide attempts.
  • This medicine could increase your heart rate. Tell your doctor if you start to have a fast or pounding heartbeat when you are at rest. You might need to check your heartbeat on a regular basis. Make sure your doctor knows if you have ever had a heart attack, stroke, rhythm problems, or heart failure.
  • This medicine may affect your mood or cause trouble sleeping. Tell your caregiver right away if you feel depressed, nervous, angry, restless, or very energetic. Make sure your doctor knows if you have ever had depression or another mood disorder. Tell your doctor if you start to have any unusual behavior.
  • Check with your doctor immediately if you have trouble seeing, blurred vision, or eye pain. These could be symptoms of glaucoma, which could cause permanent damage to your eyes. Make sure your doctor knows about any eye problems you already have.
  • This medicine may cause you to feel dizzy, drowsy, or confused, or to have trouble thinking or speaking. Avoid driving, using machines, or doing anything else that could be dangerous until you know how this medicine affects you.
  • Call your doctor if you start to have fast breathing, appetite loss, unusual tiredness or weakness, and nausea. These could be symptoms of metabolic acidosis (too much acid in the blood). You have a higher risk of metabolic acidosis if you have had it before, if you eat a ketogenic diet, when you have surgery, or if you have chronic diarrhea or bone problems such as osteoporosis.
  • For patients with type 2 diabetes who use insulin or oral diabetes medicine: Your blood sugar levels could change as you lose weight, and you are more likely to have low blood sugar. Tell your doctor if you notice any changes.
  • Do not stop using this medicine suddenly without asking your doctor. You may need to slowly decrease your dose before stopping it completely.You might have a seizure if you stop taking the medicine too fast.
  • Your blood pressure could go down when you lose weight. Tell your doctor if you start to feel dizzy or lightheaded, especially if you already take blood pressure medicine.
  • Check with your doctor right away if you have severe back or side pain or blood in your urine. These may be symptoms of a kidney stone. Make sure your doctor knows if you have had kidney stones in the past.
  • Your doctor will need to check your blood or urine at regular visits while you are using this medicine. Be sure to keep all appointments.

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
  • Bloody or dark urine, sudden back pain, stomach pain, painful urination
  • Confusion, restlessness, nervousness, unusual behavior
  • Decreased sweating, fever, or feeling hot
  • Depression, thoughts of hurting yourself, nervousness, anxiety, anger
  • Dry mouth, increased thirst, muscle cramps, nausea or vomiting, uneven heartbeat, trouble sleeping
  • Eye pain, trouble seeing
  • Fast, pounding, or uneven heartbeat
  • Fast breathing, loss of appetite, unusual tiredness, nausea
  • Seizures

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

  • Constipation
  • Metallic taste in your mouth, dry mouth
  • Mild dizziness
  • Mild trouble sleeping, without other symptoms
  • Numbness, tingling, or burning pain in your hands, arms, legs, or feet
  • Trouble remembering things or concentrating

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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