Uses, Side Effects, Dosages, Interactions

What Is Qsymia?

Qsymia is a prescription medication that, along with changes in eating habits and exercise, can aid in weight loss in certain people. It’s classified as a Schedule IV drug (controlled substance). Qsymia combines Adipex-P (phentermine), an anorexiant (reduces food intake), and Topamax (topiramate), an anti-seizure medicine. It contains a synthetic yellow dye called tartrazine. 

Qsymia works by releasing certain chemicals in the brain (hypothalamus), suppressing appetite, and reducing the amount of food you eat. However, the exact way it works is unknown.

Drug Facts

Generic Name: Phentermine and Topiramate

Brand Name(s): Qsymia

Drug Availability: Prescription

Therapeutic Classification: Anorexiant, Antiseizure

Available Generically: No

Controlled Substance: Schedule IV

Administration Route: Oral

Active Ingredient: Phentermine and Topiramate

Dosage Form(s): Capsule (extended-release)

What Is Qsymia Used For?

Qsymia (phentermine and topiramate) is used in addition to diet and exercise to help with weight loss and weight management. Body mass index (BMI), a measure of body fat in adults, is considered when prescribing this medicine.

Qsymia may be prescribed to people with a BMI greater than or equal to 30 kilograms per square meter (kg/m2) (considered obesity) or people with a BMI greater than or equal to 27 kg/m2 (considered overweight) and with one or more weight-associated medical condition.

It’s important to note that the BMI metric is thought to be flawed. BMI does not necessarily consider important body composition factors like frame size and muscle mass. And BMI definitely does not give the complete picture of an individual’s well-being.

Consider requesting a body composition test—for example, a skinfold measurement or a DEXA (dual energy X-ray absorptiometry) body composition scan—from your healthcare provider in addition to other parameters that they may measure.

It’s essential to note that obesity is also linked to a host of other social, economic, and environmental causes (known as determinants of health). These systemic issues are larger components of health that also need to be addressed.

How to Take Qsymia 

Take Qsymia as directed by your healthcare provider in the morning. Take with or without food. Do not take close to your sleep time to avoid sleep problems like insomnia.

Avoid drinking alcohol while taking Qsymia. Doing so may increase topiramate levels in your body and worsen its side effects.


Store Qsymia at room temperature (59 to 77 degrees Fahrenheit) in a dry place with a tightly closed lid. Do not store it in a bathroom or any room with moisture. Keep it in a locked box, where people may not be able to get to it. Store this medicine away from children and pets, ideally locked in a cabinet or closet.

If you plan to travel with Qsymia, get familiar with your final destination’s regulations. In general, be sure to make a copy of your Qsymia prescription. Keep your medication in its original container from your pharmacy with your name on the label. If you have any questions about traveling with your medicine, ask your pharmacist or healthcare provider.

Discard all unused and expired medications, but do not pour them down the drain or in the toilet. Ask your pharmacist or medical provider about the best ways to dispose of this medicine. And check out drug take-back programs in your area.

How Long Does Qsymia Take to Work?

Qsymia starts working immediately to suppress hunger. It lasts throughout the day. Typically, it takes about three or four hours for phentermine and two hours for topiramate to peak in your body.

What Are the Side Effects of Qsymia?

This is not a complete list of side effects and others may occur. A healthcare provider can advise you on side effects. If you experience other effects, contact your pharmacist or a healthcare provider. You may report side effects to the Food and Drug Administration (FDA) at or 800-FDA-1088.

Many people notice no negative side effects at all from taking Qsymia. However, some people do experience problems while taking the medication.

Common Side Effects

Common side effects of Qsymia include:

  • Dry mouth
  • Headache
  • Constipation
  • Dry mouth
  • Numbness and tingling in the arms, feet, or face
  • Change in taste or having a loss of taste
  • Nausea
  • Diarrhea
  • Stuffy nose
  • Loss of strength
  • Insomnia

Severe Side Effects

Qsymia can cause many side effects. Some may be life-threatening. Call your healthcare provider right away if you have serious side effects. Call 911 if your symptoms feel life-threatening or if you think you have a medical emergency. Severe side effects include:

  • Low blood sugar 
  • Mood changes
  • Muscle pain or weakness
  • Abnormal heartbeat
  • Urinary tract infection
  • Kidney stone
  • Trouble focusing
  • Trouble sleeping
  • Lack of sweat
  • Panic attacks
  • Vision changes
  • Eye redness, irritation, or pain

This medication may cause severe eye problems. If left untreated, this can result in permanent vision loss. Contact your healthcare provider if you notice any new eye symptoms, such as blurred vision, eye pain, or redness.

People taking Qsymia may have an increased risk of having thoughts or actions of suicide. Let your healthcare provider know if you have any thoughts of hurting yourself. 

Qsymia is associated with the worsening of certain health conditions, such as:

  • Glaucoma (group of diseases that can damage the optic nerve, causing vision loss)
  • Kidney stone formation
  • Suicidal ideation
  • Diabetes
  • Heart conditions, including low blood pressure
  • Cognitive dysfunction and psychiatric disturbances

Note that prolonged use of this medicine may lead to dependency. Hence, sudden discontinuation may lead to withdrawal symptoms, including seizures. Your healthcare provider may taper your dose for at least one week, taking Qsymia every other day.

Report Side Effects

Qsymia may cause other side effects. Call your healthcare provider if you have any unusual problems while taking this medication.

If you experience a serious side effect, you or your provider may send a report to the FDA’s MedWatch Adverse Event Reporting Program or by phone (800-332-1088).

Dosage: How Much of Qsymia Should I Take?

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The dose of this medicine will be different for different patients. Follow your doctor’s orders or the directions on the label. The following information includes only the average doses of this medicine. If your dose is different, do not change it unless your doctor tells you to do so.

The amount of medicine that you take depends on the strength of the medicine. Also, the number of doses you take each day, the time allowed between doses, and the length of time you take the medicine depend on the medical problem for which you are using the medicine.

  • For oral dosage form (extended-release capsules):

    • For weight loss:

      • Adults—At first, one tablet of 3.75 milligrams (mg) of phentermine and 23 mg of topiramate once a day for 14 days. After 14 days, your doctor may increase your dose to 7.5 mg of phentermine and 46 mg of topiramate once a day. Then, your doctor may increase your dose as needed up to 15 mg of phentermine and 92 mg of topiramate.
      • Children—Use is not recommended.


Severe allergic reaction: Avoid using Qsymia if you have a known allergy to it or any of its ingredients.

Pregnancy: Qsymia is harmful to an unborn fetus. It increases the risk of cleft lip (tissue making up the lip does not form completely) or cleft palate (tissue in the mouth does not fuse properly, causing an opening or split in the roof of the mouth) in your fetus, especially during the first trimester. Therefore, a negative pregnancy result is required before starting this medicine. Also, use effective contraception while on Qsymia.

Breastfeeding: Topiramate is present in breast milk. Due to the potential for adverse reactions in breastfed infants (for example, tremors, weight loss, high blood pressure), it is not recommended to breastfeed while taking this medicine.

Children: The safety of this drug in children is not established. Do not give this medicine to your child.

Adults over 65 years: This population generally tolerates Qsymia. However, doses may start at the lower range due to possible kidney or liver function differences.

Missed Dose

If you miss a dose of Qsymia, skip the missed dose and take your next dose at the regularly scheduled time. Do not double your dose or take more than one dose at a time.

Try to find ways that work for you to help yourself remember to routinely take your medication. If you miss too many doses, Qsymia might be less effective at treating your condition.

Overdose: What Happens If I Use Too Much Qsymia?

Convulsions, hallucinations, tremors, aggressiveness, and rapid breathing are possible indications of an overdose. Individuals who have consumed alcohol while on this medicine are more prone to have severe symptoms.

What Happens If I Overdose on Qsymia?

If you think you or someone else may have overdosed on Qsymia, call a healthcare provider or the Poison Control Center (800-222-1222).

If someone collapses or isn’t breathing after taking Qsymia, call 911 immediately.


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It is very important that your doctor check your progress at regular visits, to make sure that this medicine is working properly. Blood and urine tests may be needed to check for unwanted effects.

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 this medicine, tell your doctor right away.

You must have a negative pregnancy test before you will be allowed to take this medicine. You will also be required to 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.

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. Using these medicines together may cause serious unwanted effects.

This medicine may be habit-forming. If you think this medicine is not working properly after you have taken it for a few weeks, do not increase the dose. Instead, check with your doctor.

This medicine may increase your heart rate. Check with your doctor right away if you have a racing heartbeat while at rest after taking this medicine.

This medicine may cause some people to be agitated, irritable, or display other abnormal behaviors. It may also cause some people to have suicidal thoughts and tendencies or to become more depressed. If you or your caregiver notice any of these side effects, tell your doctor right away.

Check with your doctor immediately if you have a decrease in vision, blurred vision, or pain around the eyes during and after treatment with this medicine. Your doctor may want you to have your eyes checked by an eye doctor.

This medicine may cause some people to become dizzy, drowsy, or have trouble in thinking or speaking. Make sure you know how you react to this medicine before you drive, use machines, or do anything else that could be dangerous if you are not alert, well-coordinated, or able to think or see well.

This medicine may cause nausea, muscle tremors, fast breathing, problems eating, fast heartbeat, restlessness, and abdominal or stomach pain. Tell your doctor right away if you have any of these symptoms. This may be a sign that you may be having a metabolic acidosis (too much acid in the blood).

For diabetic patients: This medicine may affect blood sugar levels. If you notice a change in the results of your blood or urine sugar tests or if you have any questions, check with your doctor.

For patients with high blood pressure: This medicine may increase risk of lowering your blood pressure. If you feel dizzy, faint, or lightheaded after taking this medicine, check with your doctor.

This medicine will add to the effects of alcohol and other CNS depressants (medicines that make you drowsy or less alert). Some examples of CNS depressants are antihistamines or medicine for hay fever, other allergies, or colds, prescription pain medicines, or sleep medicines. Check with your doctor before taking any of the above while you are using this medicine.

Do not suddenly stop taking this medicine without first checking with your doctor. Stopping the medicine suddenly may cause your seizures to return or to occur more often. Your doctor may want you to gradually reduce the amount you are using before stopping completely.

Check with your doctor right away if you have sudden back pain, abdominal or stomach pain, pain while urinating, or bloody or dark urine. These may be symptoms of kidney stones.

This medicine may make you sweat less, causing your body temperature to increase. Use extra care not to become overheated during exercise or hot weather while you are taking this medicine. Overheating may result in heat stroke. Also, hot baths or saunas may make you dizzy or faint while you are taking this medicine.

This medicine may cause your body temperature to go down especially when taking valproic acid, which is a medicine to control seizures. You may have tiredness, weakness, confusion, and abnormal heartbeat and breathing. Tell your doctor right away if you feel any of these side effects.

Birth control pills (containing estrogen) may not work properly if you take them while you are taking this medicine. Unplanned pregnancies may occur. You should use a different or additional means of birth control while you are using this medicine. If you have any questions about this, check with your doctor or pharmacist.

Check with your doctor right away if you are having unusual drowsiness, dullness, tiredness, weakness, or feelings of sluggishness, mental depression or anxiety, nightmares or unusually vivid dreams, or vomiting. These may be symptoms of a serious condition called hyperammonemic encephalopathy.

Do not take other medicines unless they have been discussed with your doctor. This includes prescription or nonprescription (over-the-counter [OTC]) medicines and herbal or vitamin supplements (including any weight loss products).

What Are Reasons I Shouldn’t Take Qsymia? 

Avoid taking Qsymia if you have:

  • Hypersensitivity to phentermine (a type of stimulant) or other sympathomimetic amines, or any ingredient in its formulation
  • Glaucoma
  • A positive pregnancy test or suspected pregnancy 
  • Hyperthyroidism (overactive thyroid)
  • Used during or within 14 days after MAO-A (monoamine oxidase-A) inhibitor therapy
  • Used alcohol within six hours of taking Qsymia
  • Aniline dye allergy (tartrazine dye)

What Other Medications Interact With Qsymia?

Certain medications interact with Qsymia. These include:

What Medications Are Similar?

Other drugs similar to Qsymia that may be used to help with weight loss include:

Qsymia and liraglutide may have the highest possibility of achieving an “ideal” weight compared to other weight loss medications like Alli or Contrave.

Above is a list of medications also prescribed to help with weight loss. It is not a list of medicines recommended to take with Qsymia. You should not take these drugs together unless your healthcare provider tells you to. Ask your pharmacist or a healthcare practitioner if you have questions.

Frequently Asked Questions

  • What is Qsymia used to treat?

    Along with altering your eating habits and exercising, Qsymia can help you lose weight.

  • What are the common side effects of Qsymia?

     Some common side effects include

    • Change in taste
    • Nausea
    • Dry mouth
    • Headache
    • Numbness and tingling
    • Constipation
    • Dry mouth
    • Diarrhea
    • Stuffy nose
    • Loss of strength
    • Insomnia

  • What should I do if I miss a dose of Qsymia?

    Skip the missed dose if it is too close to the next dose. Return to your regular dosing schedule. Do not take extra doses or double the amount.

  • Where should I store Qsymia?

    Store at room temperature in a dry place with the lid tightly closed. Keep it in a locked box or locked cabinet or closet, where children, pets, and other adults will not be able to get to it.

How Can I Stay Healthy While Taking Qsymia?

Although dieting and exercise help with weight loss, they may not be enough for some people. Using weight loss pills like Qsymia may help. However, it may cause severe and sometimes long-term problems, including eye and heart issues.

Watch your body closely while on this medicine. Do not minimize any side effects that you experience. Talk to your healthcare provider immediately if you have any side effects while on this drug.

Work with a healthcare team that includes a registered dietitian (RD) or registered dietitian nutritionist (RDN)—and perhaps one who is a board-certified specialist in obesity and weight management (CSOWM). RDs/RDNs can help you explore your eating, movement, and medication habits. RDs can also help you eat better to feel better.

It can be difficult to give yourself permission to ask for and accept help. But be open when communicating your needs with your family and friends, as well as your healthcare team. You don’t have to do this alone.

Continuous data collection is being conducted to track pregnancy and baby outcomes following exposure. All pregnancies exposed to Qsymia should be reported to the Qsymia Pregnancy Surveillance Program (888-998-4887).

Medical Disclaimer

Verywell Health’s drug information is meant for educational purposes only and is not intended to replace medical advice, diagnosis, or treatment from a healthcare provider. Consult your healthcare provider before taking any new medication(s). IBM Watson Micromedex provides some of the drug content, as indicated on the page.


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