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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 had an allergic reaction to phentermine or topiramate, if you are pregnant, or if you have glaucoma or an overactive thyroid.

How to Use This Medicine:

Long Acting Capsule

  • Take your medicine as directed. Your dose may need to be changed several times to find what works best for you. Carefully follow your doctor's instructions about diet and exercise.
  • Take this medicine in the morning, with or without food. It might keep you awake if you take it at night.
  • Swallow the extended-release capsule whole. Do not crush, break, or chew it.
  • Drink extra fluids so you will urinate more often and help prevent kidney problems.
  • Your doctor should check your weight loss after 12 weeks and 24 weeks of treatment. Your treatment may change 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. Ask your pharmacist for a copy if you do not have one.
  • Missed dose: If you miss a dose or forget to take your medicine, skip the missed dose. Take your regular dose the next morning. Do not take extra medicine to make up for the missed dose.
  • Store the medicine in a closed container at room temperature, away from heat, moisture, and direct light.

Drugs and Foods to Avoid:

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

  • Do not use this medicine if you have used an MAO inhibitor (MAOI) within the past 14 days.
  • Some medicines can affect how this medicine works. Tell your doctor if you are also using acetazolamide, dichlorphenamide, methazolamide, zonisamide, a diuretic (water pill), or medicine to treat seizures (especially valproic acid, carbamazepine, phenytoin). Tell your doctor about all other diet pills that you take. Also tell him if you use birth control pills, insulin or diabetes medicine, or blood pressure medicine.
  • Do not drink alcohol while you are using this medicine. Tell your doctor if you are using any medicine that makes you sleepy, such as allergy medicine or narcotic pain 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. You should have a negative pregnancy test before you start taking this medicine and every month during your treatment. Tell your doctor right away if you miss a period.
  • Tell your doctor 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, a history of depression or suicide attempts, or seizures. Also tell him if you have ever had a heart attack, stroke, heart rhythm problems, or heart failure.
  • Rarely, this medicine may increase the risk of suicidal thoughts or actions. Contact your doctor right away if you feel depressed or have any thoughts about death, dying, or hurting yourself.
  • This medicine could cause the following problems:
    • Glaucoma
    • Metabolic acidosis
    • Kidney stones
    • An increased heart rate
    • Changes in blood sugar levels
    • A lower blood pressure
  • This medicine may cause you to feel dizzy, drowsy, or confused, or to have trouble thinking or speaking. Do not drive or do anything else that could be dangerous until you know how this medicine affects you.
  • Do not stop using this medicine suddenly. Your doctor will need to slowly decrease your dose before you stop it completely. You might have a seizure if you stop taking the medicine too fast.
  • Keep all medicine out of the reach of children. Never share your medicine with anyone.

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, anxiety, anger
  • Dry mouth, increased thirst, muscle cramps, nausea or vomiting, uneven heartbeat, trouble sleeping
  • Fast, pounding, or uneven heartbeat
  • Fast breathing, loss of appetite, unusual tiredness, nausea
  • Seizures
  • Vision loss, blurred vision, eye pain

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

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

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 Updated: 11/4/2014
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