Phentermine/topiramate (By mouth)

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

Used 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:

This medicine is not right for everyone. Do not use it if you had an allergic reaction to phentermine or topiramate, 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.
  • 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 phentermine/topiramate works. Tell your doctor if you are using the following:
    • Acetazolamide, dichlorphenamide, methazolamide, zonisamide
    • Birth control pills
    • Other diet pills (including nonprescription or herbal products)
    • Diuretic (water pill)
    • Medicine to treat seizures (such as valproic acid, carbamazepine, phenytoin)
  • Tell your doctor if you use anything else that makes you sleepy. Some examples are allergy medicine, narcotic pain medicine, and alcohol.
  • 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. You should have a negative pregnancy test before you start taking this medicine and every month during 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, diabetes, heart failure, heart rhythm problems, or a history of stroke or heart attack.
  • Rarely, this medicine may increase the risk of suicidal thoughts or actions. Tell your doctor if you have a history of depression or suicide attempts.
  • This medicine could cause the following problems:
    • Vision problems or glaucoma
    • Metabolic acidosis (too much acid in the blood)
    • An increased heart rate
    • Changes in blood sugar levels
    • Kidney stones
  • 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.
  • Your doctor will do lab tests at regular visits to check on the effects of this medicine. Keep all appointments.
  • 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
  • Decreased sweating, fever, or feeling hot
  • Dry mouth, increased thirst, muscle cramps, nausea or vomiting
  • Eye pain, vision changes, seeing halos around lights
  • Fast breathing, loss of appetite, unusual tiredness
  • Fast, pounding, or uneven heartbeat
  • Lightheadedness, dizziness, or fainting
  • Problems with speech or memory, trouble concentrating, confusion
  • Seizures
  • Thoughts of hurting yourself, depression, anxiety, trouble sleeping

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

  • Constipation
  • Metallic taste in your mouth, dry mouth
  • 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: 11/6/2020

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