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Phentermine and topiramate (Oral)

Generic name: phentermine and topiramate [ FEN-ter-meen- hye-droe-KLOR-ide, toe-PIR-a-mate ]
Brand name: Qsymia
Drug class: Anorexiants

Medically reviewed by Drugs.com. Last updated on Feb 18, 2024.

Uses for phentermine and topiramate

Phentermine and topiramate combination is used together with a reduced-calorie diet and proper exercise to help you lose weight. It is also used in overweight people who may also have diabetes, high blood pressure, high cholesterol, or heart disease.

This medicine is available only under a special restricted distribution program called Qsymia® REMS program.

Before using phentermine and topiramate

In deciding to use a medicine, the risks of taking the medicine must be weighed against the good it will do. This is a decision you and your doctor will make. For this medicine, the following should be considered:

Allergies

Tell your doctor if you have ever had any unusual or allergic reaction to this medicine or any other medicines. Also tell your health care professional if you have any other types of allergies, such as to foods, dyes, preservatives, or animals. For non-prescription products, read the label or package ingredients carefully.

Pediatric

Appropriate studies have not been performed on the relationship of age to the effects of phentermine and topiramate combination in children younger than 12 years of age. Safety and efficacy have not been established.

Geriatric

Appropriate studies performed to date have not demonstrated geriatric-specific problems that would limit the usefulness of phentermine and topiramate combination in the elderly. However, elderly patients are more likely to have kidney, liver, or heart problems, which may require caution and an adjustment in the dose for patients receiving phentermine and topiramate combination.

Breast Feeding

There are no adequate studies in women for determining infant risk when using this medication during breastfeeding. Weigh the potential benefits against the potential risks before taking this medication while breastfeeding.

Interactions with Medicines

Although certain medicines should not be used together at all, in other cases two different medicines may be used together even if an interaction might occur. In these cases, your doctor may want to change the dose, or other precautions may be necessary. When you are taking this medicine, it is especially important that your healthcare professional know if you are taking any of the medicines listed below. The following interactions have been selected on the basis of their potential significance and are not necessarily all-inclusive.

Using this medicine with any of the following medicines is not recommended. Your doctor may decide not to treat you with this medication or change some of the other medicines you take.

Using this medicine with any of the following medicines is usually not recommended, but may be required in some cases. If both medicines are prescribed together, your doctor may change the dose or how often you use one or both of the medicines.

Using this medicine with any of the following medicines may cause an increased risk of certain side effects, but using both drugs may be the best treatment for you. If both medicines are prescribed together, your doctor may change the dose or how often you use one or both of the medicines.

Interactions with Food/Tobacco/Alcohol

Certain medicines should not be used at or around the time of eating food or eating certain types of food since interactions may occur. Using alcohol or tobacco with certain medicines may also cause interactions to occur. The following interactions have been selected on the basis of their potential significance and are not necessarily all-inclusive.

Using this medicine with any of the following is not recommended. Your doctor may decide not to treat you with this medication, change some of the other medicines you take, or give you special instructions about the use of food, alcohol, or tobacco.

Other Medical Problems

The presence of other medical problems may affect the use of this medicine. Make sure you tell your doctor if you have any other medical problems, especially:

Proper use of phentermine and topiramate

Take this medicine only as directed by your doctor. Do not take more of it, do not take it more often, and do not take it for a longer time than your doctor ordered. If too much is taken, it may become habit-forming (causing mental or physical dependence).

This medicine comes with a Medication Guide. Read and follow the instructions carefully. Ask your doctor if you have any questions.

Take this medicine once a day in the morning, with or without food. Avoid taking this medicine in the evening to prevent trouble sleeping.

Swallow the extended-release capsule whole. Do not crush, break, or chew it.

Carefully follow your doctor's instructions for a reduced-calorie diet plan and regular exercise. Talk with your doctor before starting any exercise program.

Your doctor should tell you to stop taking this medicine if you do not lose a certain amount of weight within the first 12 weeks of treatment.

It is important that you drink extra water every day while you take this medicine to help prevent kidney stones.

Dosing

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.

Missed Dose

If you miss a dose of this medicine, take it as soon as possible. However, if it is almost time for your next dose, skip the missed dose and go back to your regular dosing schedule. Do not double doses.

Storage

Store the medicine in a closed container at room temperature, away from heat, moisture, and direct light. Keep from freezing.

Keep out of the reach of children.

Do not keep outdated medicine or medicine no longer needed.

Ask your healthcare professional how you should dispose of any medicine you do not use.

Detailed Phentermine / topiramate dosage information

Precautions while using phentermine and topiramate

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, change in near or distance 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).

This medicine may decrease the density of bones, which can make your bones weak. Talk with your doctor if you have any concerns about this.

This medicine may cause slow growth. For children, the doctor will need to keep track of height and weight to make sure that the child is growing properly.

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, 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.

Check with your doctor right away if you have decreased urine, dry mouth, irregular heartbeat, increased thirst, loss of appetite, mood changes, muscle pain or cramps, nausea or vomiting, numbness or tingling in the hands, feet, or lips, seizures, trouble breathing, or unusual tiredness or weakness. These may be symptoms of hypokalemia.

Serious skin reactions (eg, Stevens-Johnson syndrome, toxic epidermal necrolysis) can occur with this medicine. Check with your doctor right away if you have blistering, peeling, or loosening of the skin, chills, cough, diarrhea, itching, joint or muscle pain, red irritated eyes, red skin lesions, often with a purple center, sore throat, sores, ulcers, or white spots in the mouth or on the lips, or unusual tiredness or weakness with 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).

Side Effects of phentermine and topiramate

Along with its needed effects, a medicine may cause some unwanted effects. Although not all of these side effects may occur, if they do occur they may need medical attention.

Check with your doctor immediately if any of the following side effects occur:

Less common

Rare

Incidence not known

Some side effects may occur that usually do not need medical attention. These side effects may go away during treatment as your body adjusts to the medicine. Also, your health care professional may be able to tell you about ways to prevent or reduce some of these side effects. Check with your health care professional if any of the following side effects continue or are bothersome or if you have any questions about them:

More common

Less common

Incidence not known

Other side effects not listed may also occur in some patients. If you notice any other effects, check with your healthcare professional.

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

Phentermine / topiramate side effects (more detail)

Commonly used brand name(s)

In the U.S.

Available Dosage Forms:

Therapeutic Class: Appetite Suppressant, Centrally Acting

Chemical Class: Phentermine

Further information

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.

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