Update Date 12/05/2020
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What is Qsymia® (phentermine and topiramate) used for?

Qsymia® is used together with diet and exercise to treat obesity. This medicine is sometimes used to treat obesity that may be related to diabetes, high cholesterol, or high blood pressure.

Qsymia® will not treat any these underlying conditions.

How should I take Qsymia® (phentermine and topiramate)?

Take Qsymia® by mouth with or without food as directed by your doctor, usually once daily in the morning. Taking this medication late in the day may cause trouble sleeping (insomnia). Swallow the capsules whole. Do not crush or chew the capsules. Doing so can release all of the drug at once, increasing the risk of side effects.

The dosage is based on your medical condition and response to treatment. To reduce your risk of side effects, your doctor may direct you to start this medication at a low dose and gradually increase your dose. Follow your doctor’s instructions carefully.

To prevent kidney stones from forming, drink plenty of liquids while taking this medication unless your doctor instructs you otherwise.

Qsymia® should not be taken with other appetite suppressants (see also Drug Interactions section). The possibility of serious side effects increases with longer use of this medication and use of this drug along with certain other diet drugs.

Qsymia® may cause withdrawal reactions, especially if it has been used regularly for a long time or in high doses. In such cases, withdrawal symptoms (such as seizures) may occur if you suddenly stop using this medication. To prevent withdrawal reactions, your doctor may reduce your dose gradually. Consult your doctor or pharmacist for more details, and report any withdrawal reactions right away.

Along with its benefits, Qsymia® may rarely cause abnormal drug-seeking behavior (addiction). This risk may be increased if you have abused alcohol or drugs in the past. Do not increase your dose or use this drug more often or for longer than prescribed. Your condition will not improve any faster, and your risk of side effects will increase. Take this medication exactly as prescribed to lessen the risk of addiction.

Since this drug can be absorbed through the skin and lungs and may harm an unborn baby, women who are pregnant or who may become pregnant should not handle this medication.

When Qsymia® is used for several weeks, it may not work as well. Talk with your doctor if this medication stops working well. Your doctor may direct you to stop taking this medication.

How do I store Qsymia® (phentermine and topiramate)?

Qsymia® is best stored at room temperature away from direct light and moisture. To prevent drug damage, you should not store Qsymia® in the bathroom or the freezer. There may be different brands of Qsymia® that may have different storage needs. It is important to always check the product package for instructions on storage, or ask your pharmacist. For safety, you should keep all medicines away from children and pets.

You should not flush Qsymia® down the toilet or pour them into a drain unless instructed to do so. It is important to properly discard this product when it is expired or no longer needed. Consult your pharmacist for more details about how to safely discard your product.

Precautions & warnings

What should I know before using Qsymia® (phentermine and topiramate)?

Before using this drug, tell your doctor if:

  • You are pregnant or breastfeeding. This is because, while you are expecting or feeding a baby, you should only take medicines on the recommendation of a doctor.
  • You are taking any other medicines. This includes any medicines you are taking which are available to buy without a prescription, such as herbal and complementary medicines.
  • You have allergy with any of active or inactive ingredients of Qsymia® or other medications.
  • You have any other illnesses, disorders, or medical conditions.

Do not use Qsymia® if you have used an MAO inhibitor in the past 14 days. A dangerous drug interaction could occur. MAO inhibitors include isocarboxazid, linezolid, methylene blue injection, phenelzine, rasagiline, selegiline, tranylcypromine, and others.

You should not use Qsymia® if you have:

  • Glaucoma
  • Overactive thyroid

Qsymia® can cause irregular vaginal bleeding while you are taking birth control pills. This should not make the pills less effective in preventing pregnancy.

It is not known whether phentermine and topiramate passes into breast milk or if it could harm a nursing baby. You should not breast-feed while using this medicine.

Qsymia® is not approved for use by anyone younger than 18 years old.

Is it safe during pregnancy or breastfeeding?

There are no adequate studies in women for determining risk when using Qsymia® during pregnancy or while breastfeeding. Please always consult with your doctor to weigh the potential benefits and risks before taking Qsymia®. Qsymia® is pregnancy risk category X, according to the US Food and Drug Administration (FDA).

FDA pregnancy risk category reference below:

  • A=No risk
  • B=No risk in some studies
  • C=There may be some risk
  • D=Positive evidence of risk
  • X=Contraindicated
  • N=Unknown

Side effects

What side effects can occur from Qsymia® (phentermine and topiramate)?

Get emergency medical help if you have signs of an allergic reaction to Qsymia®: hives; difficulty breathing; swelling of your face, lips, tongue, or throat.

Report any new or worsening symptoms to your doctor, such as: mood or behavior changes, anxiety, panic attacks, trouble sleeping, or if you feel impulsive, irritable, agitated, hostile, aggressive, restless, hyperactive (mentally or physically), more depressed, or have thoughts about suicide or hurting yourself.

Call your doctor at once if you have:

  • Pounding heartbeats or fluttering in your chest (even if you are resting)
  • Sudden vision problems, sometimes with eye pain or redness
  • Trouble concentrating, problems with speech or memory
  • A seizure (convulsions)
  • Feeling very thirsty or hot, decreased sweating, hot and dry skin
  • Low blood sugar–headache, hunger, weakness, sweating, irritability, dizziness, or feeling jittery
  • Signs of metabolic acidosis–confusion, vomiting, lack of energy, irregular heartbeats
  • Signs of a kidney stone–pain in your side or lower back, blood in your urine, painful or difficult urination

Common side effects may include:

  • Dizziness
  • Constipation
  • Numbness or tingly feeling
  • Sleep problems (insomnia)
  • Dry mouth, changes in your sense of taste

Not everyone experiences these side effects. There may be some side effects not listed above. If you have any concerns about a side-effect, please consult your doctor or pharmacist.


What drugs may interact with Qsymia® (phentermine and topiramate)?

Qsymia® may interact with other drugs that you are currently taking, which can change how your drug works or increase your risk for serious side effects. To avoid any potential drug interactions, you should keep a list of all the drugs you are using (including prescription drugs, nonprescription drugs, and herbal products) and share it with your doctor and pharmacist. For your safety, do not start, stop, or change the dosage of any drugs without your doctor’s approval.

Products that may interact with this drug are:

  • Acetazolamide
  • Methazolamide
  • Zonisamide
  • Valproic acid or divalproex sodium (Depakene or Depakote)
  • Birth control pills
  • A diuretic or “water pill”

Does food or alcohol interact with Qsymia® (phentermine and topiramate)?

Qsymia® may interact with food or alcohol by altering the way the drug works or increase the risk for serious side effects. Please discuss with your doctor or pharmacist any potential food or alcohol interactions before using this drug.

What health conditions may interact with Qsymia® (phentermine and topiramate)?

Qsymia® may interact with your health condition. This interaction may worsen your health condition or alter the way the drug works. It is important to always let your doctor and pharmacist know all the health conditions you currently have.

Health conditions that may interact with this drug are:

  • High blood pressure, heart disease, heart rhythm problems, congestive heart failure
  • A history of heart attack or stroke
  • A history of depression, mental illness, or suicidal thoughts
  • Diabetes
  • Kidney disease (or if you are on dialysis)
  • History of kidney stones
  • Liver disease
  • Seizures or epilepsy
  • Low bone mineral density
  • Metabolic acidosis (too much acid in your blood)


The information provided is not a substitute for any medical advice. You should ALWAYS consult with your doctor or pharmacist before using Qsymia® (phentermine and topiramate).

What is the dose of Qsymia® (phentermine and topiramate) for an adult?

Usual Adult Dose for Weight Loss:

Initial dose: Take one capsule of the lowest dose (phentermine 3.75 mg/topiramate 23 mg extended-release) orally once a day in the morning for the first 14 days.

Maintenance dose: After 14 days, take one capsule of the recommended dose (phentermine 7.5 mg/topiramate 46 mg extended-release) orally once a day in the morning.

What is the dose of Qsymia® (phentermine and topiramate) for a child?

The dosage has not been established in pediatric patients. It may be unsafe for your child. It is always important to fully understand the safety of the drug before using. Please consult with your doctor or pharmacist for more information.

How is Qsymia® (phentermine and topiramate) available?

Qsymia® is available in the following dosage forms and strengths: phentermine

  • Capsule, extended release: hydrochloride 3.75mg, topiramate 23mg

What should I do in case of an emergency or overdose?

In case of an emergency or an overdose, call your local emergency services or go to your nearest emergency room.

What should I do if I miss a dose?

If you miss a dose of Qsymia®, take it as soon as possible. However, if it is almost time for your next dose, skip the missed dose and take your regular dose as scheduled. Do not take a double dose.

Hello Health Group does not provide medical advice, diagnosis or treatment.

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