Phentermine & Topiramate

The combination of phentermine/topiramate is used to help adults lose weight if they are obese or overweight and have weight-related medical problems. It must be used along with diet and exercise.

Phentermine & Topiramate Overview

Reviewed: June 21, 2015
Updated: 

Phentermine/topiramate is a prescription medication used to help adults who are obese or overweight and have weight-related medical problems. Phentermine/topiramate helps these adults lose weight and maintain a healthy weight.

It is a single product containing 2 medications: phentermine/topiramate.

Phentermine belongs to a group of drugs called anorectics. These work by reducing appetite and help to decrease food consumption. Topiramate belongs to a group of drugs called anticonvulsants. These work by reducing appetite and increasing a feeling of fullness after eating.

This medication comes in extended-release capsule form and is taken 1 time a day, with or without food. Take phentermine/topiramate in the morning.

Common side effects of phentermine/topiramate include changes in the way foods taste, trouble sleeping, constipation, dry mouth, and numbness or tingling in the hands, arms, feet, or face.

Phentermine/topiramate can also cause blurred vision, drowsiness, and dizziness. Do not drive or operate heavy machinery until you know how phentermine/topiramate affects you.

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Phentermine & Topiramate Cautionary Labels

precautionsprecautionsprecautions

Uses of Phentermine & Topiramate

Phentermine/topiramate is a prescription medication used to help adults who are obese or overweight and have weight-related medical problems. Phentermine/topiramate helps these adults lose weight and maintain a healthy weight.

Phentermine & Topiramate Brand Names

Phentermine & Topiramate may be found in some form under the following brand names:

Side Effects of Phentermine & Topiramate

Serious side effects have been reported with phentermine/topiramate. See the “Phentermine & Topiramate Precautions” section.

Common side effects of phentermine/topiramate include the following:

  • headache
  • dizziness
  • numbness, burning, or tingling in the hands, feet, face, or mouth
  • decreased sense of touch or ability to feel sensation
  • difficulty concentrating, thinking, paying attention, speaking, or remembering
  • excessive tiredness
  • dry mouth
  • unusual thirst
  • changes or decreased ability to taste food
  • diarrhea
  • constipation
  • heartburn
  • painful menstrual periods
  • pain in the back, neck, muscles, arms or legs
  • tightening of the muscles
  • painful, difficult, or frequent urination
  • hair loss

This is not a complete list of phentermine/topiramate side effects. Ask your doctor or pharmacist for more information.

Tell your doctor if you have any side effect that bothers you or that does not go away.

Call your doctor for medical advice about side effects. You may report side effects to the FDA at 1-800-FDA-1088.

Phentermine & Topiramate Interactions

Tell your doctor about all the medicines you take, including prescription and non-prescription medicines, vitamins, and herbal supplements. Especially tell your doctor if you take:

  • a monoamine oxidase inhibitor (MAOI) including isocarboxazid (Marplan), phenelzine (Nardil), selegiline (Eldepryl, Emsam, Zelapar), and tranylcypromine (Parnate), or if you have taken one of these medications during the past two weeks
  • amitriptyline (Elavil)
  • birth control pills
  • carbonic anhydrase inhibitors such as acetazolamide (Diamox), methazolamide, or zonisamide (Zonegran)
  • diuretics ('water pills') including furosemide (Lasix) or hydrochlorothiazide (HCTZ); insulin or other medications for diabetes
  • ipratropium (Atrovent)
  • lithium (Lithobid)
  • medications for anxiety, high blood pressure, irritable bowel disease, mental illness, motion sickness, Parkinson's disease, ulcers, or urinary problems; medications for seizures such as carbamazepine (Carbatrol, Equetro, Tegretol), phenytoin (Dilantin), or valproic acid (Stavzor, Depakene)
  • pioglitazone (Actos, in Actoplus, in Duetact)
  • sedatives
  • sleeping pills
  • tranquilizers

This is not a complete list of phentermine/topiramate drug interactions. Ask your doctor or pharmacist for more information.

Phentermine & Topiramate Precautions

Serious side effects have been reported with phentermine/topiramate including the following:

  • Fetal toxicity. If you take phentermine/topiramate during pregnancy, your baby may develop a birth defect called cleft lip or cleft palate. Your baby may develop this birth defect very early in the pregnancy, before you know that you are pregnant. You must use birth control to prevent pregnancy during your treatment. You must take a pregnancy test before you begin your treatment and once every month during your treatment. If you become pregnant while taking phentermine and topiramate, stop taking the medication and call your doctor immediately.
  • Increased heart rate. Check your resting heart rate regularly while taking phentermine/topiramate and you’re your health care provider about feelings of a racing heart beat or palpitations.
  • Mental health changes. You, your family, or your caregiver should call your doctor right away if you experience any of the following symptoms: panic attacks; agitation or restlessness; new or worsening irritability, anxiety, or depression; acting on dangerous impulses; difficulty falling or staying asleep; aggressive, angry, or violent behavior; mania (frenzied, abnormally excited mood); talking or thinking about wanting to hurt yourself or end your life; withdrawing from friends and family; preoccupation with death and dying; giving away prized possessions; or any other unusual changes in behavior or mood. Be sure that your family or caregiver knows which symptoms may be serious so they can call the doctor if you are unable to seek treatment on your own.
  • Cognitive impairment. Tell your health care provider if you experience any of the following symptoms:
    • changes in concentration or attention
    • difficulty with memory
    • speech or language problems
  • Vision changes, including secondary angle closure glaucoma. Tell your health care provider if you experience any of the following symptoms:
    • changes in visual acuity
    • eye pain
    • eye redness
  • Kidney stone formation. Drink extra fluids while taking phentermine/topiramate to reduce the likelihood of developing kidney stones. Tell your health care provider if you experience any of the following symptoms:
    • severe pain in the back or side
    • blood in urine
  • Metabolic changes. Tell your health care provider if you experience any of the following symptoms:
    • fast, shallow breathing
    • fatigue
    • changes in heart rate

Phentermine/topiramate can also cause blurred vision, drowsiness, and dizziness. Do not drive or operate heavy machinery until you know how phentermine/topiramate affects you.

Do not take phentermine/topiramate if you:

  • are allergic to phentermine/topiramate or to any of its ingredients
  • are pregnant
  • have glaucoma
  • have hyperthyroidism
  • have taken a monoamine oxidase inhibitor in the last 14 days
  • have had an allergic or hypersensitivity reaction to sympathomimetic amine medications such as midodrine (Orvaten, ProAmatine) or phenylephrine (in cough and cold medications)

Phentermine & Topiramate Food Interactions

Medications can interact with certain foods. In some cases, this may be harmful and your doctor may advise you to avoid certain foods. In the case of phentermine/topiramate, there are no specific foods that you must exclude from your diet when receiving this medication.

Inform MD

Before taking phentermine/topiramate, tell your doctor about all of your medical conditions. Especially tell your doctor if you:

  • are allergic to phentermine/topiramate or have had an allergic or hypersensitivity reaction to sympathomimetic amine medications such as midodrine (Orvaten, ProAmatine) or phenylephrine (in cough and cold medications)
  • have had a heart attack or a stroke in the past 6 months
  • have ever thought about killing yourself or tried to do so
  • are following a ketogenic diet (high fat, low carbohydrate diet used to control seizures)
  • have or have ever had depression
  • have an irregular heartbeat
  • have heart failure
  • have seizures
  • have metabolic acidosis (too much acid in the blood)
  • have bone diseases such as osteopenia, osteomalacia, or osteoporosis (conditions in which the bones are brittle or weak and may break easily)
  • have ongoing diarrhea
  • have any condition that affects your breathing
  • have diabetes
  • have kidney stones
  • have kidney or liver disease

Tell your doctor about all the medicines you take including prescription and non-prescription medicines, vitamins, and herbal supplements.

Phentermine & Topiramate and Pregnancy

Tell your doctor if you are pregnant or plan to become pregnant.

The FDA categorizes medications based on safety for use during pregnancy. Five categories - A, B, C, D, and X - are used to classify the possible risks to an unborn baby when a medication is taken during pregnancy.

Phentermine/topiramate falls into category X.

It has been shown that women taking phentermine/topiramate during pregnancy may have babies born with problems. There are no situations where the benefits of the medication for the mother outweigh the risks of harm to the baby. This medicine should never be used by pregnant women.

Phentermine & Topiramate and Lactation

Tell your doctor if you are breastfeeding or plan to breastfeed.

Phentermine/topiramate may be present in human breast milk. Because of the possibility for adverse reactions in nursing infants from phentermine/topiramate, a choice should be made whether to stop nursing or to stop use of this medication. The importance of the drug to the mother should be considered.

Phentermine & Topiramate Usage

Take phentermine/topiramate exactly as prescribed.

Phentermine/topiramate comes in extended-release capsule form and is taken once daily, in the morning. It may be taken with or without food.

If you miss a dose, take the missed dose the next morning. If it is almost time for the next dose, skip the missed dose and take your next dose at the regular time. Do not take 2 doses of phentermine/topiramate at the same time.

You should avoid drinking alcohol while taking phentermine/topiramate.

Phentermine & Topiramate Dosage

Take this medication exactly as prescribed by your doctor. Follow the directions on your prescription label carefully.

The dose your doctor recommends may be based on the following:

  • other medical conditions you have
  • other medications you are taking
  • how you respond to this medication
  • your weight
  • your height

The recommended dose of phentermine/topiramate is based on body mass index, which is calculated using a patient’s height and weight.

Phentermine & Topiramate Overdose

If you take too much phentermine/topiramate, call your healthcare provider or local Poison Control Center, or seek emergency medical attention right away.

If phentermine/topiramate is administered by a healthcare provider in a medical setting, it is unlikely that an overdose will occur. However, if overdose is suspected, seek emergency medical attention.

Other Requirements

  • Store phentermine/topiramate at room temperature.
  • Keep this and all medicines out of the reach of children.
  • Phentermine/topiramate is not available at retail pharmacies. This medication is available only through specific mail order pharmacies.

Phentermine & Topiramate FDA Warning

Phentermine/topiramate is a federally controlled substance (CIV) because it contains phentermine and can be abused or lead to drug dependence. Keep phentermine/topiramate in a safe place, to protect it from theft. Never give your phentermine/topiramate to anyone else, because it may cause death or harm them. Selling or giving away this medicine is against the law.