Phentermine and topiramate extended-release
Combination anorectic and antiepileptic. Sold as Qsymia.
Qsymia combines phentermine with topiramate, a medication originally approved for seizures and migraine. Unlike phentermine on its own, this combination is approved for long-term weight management, and it is approved in adolescents aged 12 and older as well as adults.
Brands and what each one is approved for
One active ingredient can hold several separate FDA approvals. They are different documents with different approved uses, and mixing them up is the most common mistake made about these medications.
| Brand | Status for this use | Supply | Label version |
|---|---|---|---|
| QsymiaVivus LLC | Approved for weight loss | Prescription | 22 April 2026 |
How it works
Written by us
The label states that the mechanism by which the combination produces weight loss is not fully understood. Phentermine acts as an appetite suppressant. Topiramate's contribution to weight loss is described in the label as not established, and its effects are attributed to several actions on the nervous system.
From the mechanism of action section of the Qsymia label
Phentermine is a sympathomimetic amine with pharmacologic activity similar to the prototype drugs of this class used in obesity, amphetamine (d- and d/l-amphetamine). Drugs of this class used in obesity are commonly known as "anorectics" or "anorexigenics." The effect of phentermine on weight reduction and long-term maintenance of body weight is likely...
What the FDA approved it for
The approved uses, as worded in the label.
From the FDA label
- QSYMIA is indicated in combination with a reduced-calorie diet and increased physical activity to reduce excess body weight and maintain weight reduction long term in: Adults and pediatric patients aged 12 years and older with obesity Adults with overweight in the presence of at least one weight-related comorbid condition QSYMIA is a combination of phentermine, a sympathomimetic amine anorectic,...
- Adults with overweight in the presence of at least one weight-related comorbid condition.
- Limitations of Use: The effect of QSYMIA on cardiovascular morbidity and mortality has not been established.
- The safety and effectiveness of QSYMIA in combination with other products intended for weight loss, including prescription and over-the-counter drugs, and herbal preparations, have not been established.
Forms and strengths
The presentations and strengths listed in the label.
From the FDA label
QSYMIA extended-release capsules are available in four strengths (phentermine mg/topiramate mg): 3.75 mg/23 mg - purple cap imprinted with VIVUS and purple body imprinted with 3.75/23 7.5 mg/46 mg -...
How the label says it is taken
What the label states about administration. It is not a dosing instruction for any individual.
From the FDA label
- Take orally once daily in morning.
- Avoid administration in evening to prevent insomnia.
- Recommended starting dosage is 3.75 mg/23 mg (phentermine mg/topiramate mg) daily for 14 days; then increase to 7.5 mg/46 mg daily.
- Escalate dosage based on weight loss in adults or BMI reduction in pediatric patients.
Most common adverse reactions
The adverse reactions the label reports as most common.
From the FDA label
Most common adverse reactions in: Adults (incidence ≥ 5% and at least 1.5 times placebo) are: paraesthesia, dizziness, dysgeusia, insomnia, constipation, and dry mouth (6.
Warnings and precautions
The warnings and precautions section of the label.
From the FDA label
- Embryo-Fetal Toxicity: Can cause fetal harm.
- In patients who can become pregnant, a negative pregnancy test is recommended before initiating QSYMIA and monthly during therapy; advise use of effective contraception.
- QSYMIA is available through a limited program under a Risk Evaluation and Mitigation Strategy (REMS).
- Suicidal Behavior and Ideation: Monitor for depression or suicidal thoughts.
Contraindications
Situations in which the label states the medication must not be used.
From the FDA label
- QSYMIA is contraindicated in patients: Who are pregnant With glaucoma With hyperthyroidism Taking or within 14 days of stopping a monoamine oxidase inhibitors With known hypersensitivity to phentermine, topiramate or any of the excipients in QSYMIA, or idiosyncrasy to the sympathomimetic amines.
- Anaphylaxis and angioedema have occurred with topiramate Pregnancy Glaucoma Hyperthyroidism Taking or within 14 days of stopping monoamine oxidase inhibitors Known hypersensitivity to any component of QSYMIA or idiosyncrasy to sympathomimetic amines
Drug interactions
Interactions the label singles out.
From the FDA label
- Table 5 displays clinically significant drug interactions with QSYMIA.
- Clinically Significant Drug Interactions with QSYMIA Monoamine Oxidase Inhibitors Clinical Impact Concomitant use of phentermine with monoamine oxidase inhibitors (MAOIs) increases the risk of hypertensive crisis.
- Intervention Concomitant use of QSYMIA is contraindicated during MAOI treatment and within 14 days of stopping an MAOI.
- Oral Contraceptives Clinical Impact Co-administration of multiple-dose QSYMIA 15 mg/92 mg once daily with a single dose of oral contraceptive containing 35 µg ethinyl estradiol (estrogen component) and 1 mg norethindrone (progestin component), in obese otherwise healthy volunteers, decreased the exposure of ethinyl estradiol by 16% and increased the exposure of norethindrone by 22%.
Pregnancy and breastfeeding
The opening of the pregnancy section of the label. The full section is longer and is in the source document.
From the FDA label
QSYMIA is contraindicated in pregnant patients. The use of QSYMIA can cause fetal harm, and weight loss offers no clear clinical benefit to a pregnant patient (see Clinical Considerations). Available data from pregnancy registries and epidemiologic studies indicate an increased risk of major congenital malformations, including but not limited to cleft lip and/or cleft palate (oral clefts), and of being SGA in infants exposed in utero to topiramate (see Data).
Generic or brand
Written by us
Generic versions of the phentermine and topiramate extended-release combination have been approved in the United States. The individual ingredients have long been available as separate generics, but that is not the same product as the approved combination.
The FDA label database lists 2 approved generic applications for this ingredient.
What affects the cost
Written by us
The label requires pregnancy testing before treatment and monthly during treatment, which shapes how this medication is prescribed and followed up. This site does not track prices and does not link to sellers.
Common questions
- Why does Qsymia contain a seizure medication?
- Topiramate is approved on its own for epilepsy and for migraine prevention. Weight loss was observed as an effect in its trials, and the combination with phentermine was later developed and approved specifically for weight management. The label states that the mechanism of the weight loss effect is not fully understood.
- Can Qsymia be taken during pregnancy?
- The label contraindicates it in pregnancy and states that topiramate increases the risk of oral clefts when taken in the first trimester. Pregnancy testing before treatment and monthly during treatment is described in the label.
Sources
Every fact above comes from one of these documents. The date is the effective date of the label version this page was built from.
FDA prescribing information for Qsymia
Vivus LLC. Label version 42, effective 22 April 2026.
Page last updated: 29 July 2026
Compiled by the HealthyStudy editorial team from FDA source documents. No medical reviewer is credited on this page, because none reviewed it.