Phentermine And Topiramate
Pronunciation: (kew-SIM-ee-uh).
- Generic name
- Phentermine and Topiramate
- Brand names
- Slimtop, Qsymia, Phentop
- Drug class
- Anorexiant; Anticonvulsant Combination; Weight Management Agent
Availability and supply rules vary by country
Trade names by country: United States
Australia: · Full directory
What Phentermine and Topiramate is and how it works
Uses, formulations, monitoring, and supply rules can differ by patient, product, and country. Follow the exact local product information and professional advice.
Mechanism of action: how Phentermine and Topiramate works
Phentermine is a sympathomimetic amine that stimulates the release of norepinephrine in the hypothalamus, suppressing appetite. Topiramate is an anticonvulsant that promotes weight loss through modulation of voltage-gated ion channels, enhancement of GABA activity, inhibition of AMPA/kainate glutamate receptors, and inhibition of carbonic anhydrase. The combination results in synergistic appetite suppression and enhanced satiety. (2)
What Phentermine and Topiramate is used for
Chronic weight management
Chronic weight management (2)
Obesity
Obesity (2)
Weight loss in adults with a BMI of 30 kg/m² or greater
Weight loss in adults with a BMI of 30 kg/m² or greater (2)
Weight loss in adults with a BMI of 27 kg/m² or greater with at least one weight-related comorbidity
Weight loss in adults with a BMI of 27 kg/m² or greater with at least one weight-related comorbidity (2)
Before taking Phentermine and Topiramate
Do not take / not appropriate for
- Pregnancy, glaucoma, hyperthyroidism, recent or current MAOI use, hypersensitivity to components. (Contraindication) (2)
Tell your clinician about
(2)How to take Phentermine and Topiramate
- General Instructions: Take Qsymia exactly as prescribed by your healthcare provider. Do not increase your dose or take it more often than directed.. Adult Dosing: Start with the lowest dose (3.75 mg/23 mg once daily) for 14 days, then increase to 7.5 mg/46 mg once daily. Dose may be increased further based on response and tolerability, up to a maximum of 15 mg/92 mg once daily.. Pediatric Dosing: Safety and efficacy have not been established in patients under 18 years of age.. Administration: Take Qsymia once daily in the morning, with or without food. Swallow capsules whole; do not crush, chew, or split.. When To Stop: If you do not lose at least 3% of your body weight after 12 weeks on the recommended dose, your doctor may discontinue Qsymia or adjust your dose.. Storage: Store at room temperature (20°C to 25°C/68°F to 77°F), away from moisture and heat. Keep out of reach of children.
- This page does not provide a dose calculator. Dosing must follow the prescriber, pharmacist, or product label.
Procedures and treatment changes
Tell the treating team before surgery, procedures, or any medicine change. Do not alter treatment without the responsible clinician. (2)
Missed dose
If you miss a dose, take it as soon as you remember, unless it is late in the day. If it is close to your next dose, skip the missed dose. Do not double up to make up for a missed dose.
Overdose
In case of overdose, seek emergency medical attention or call your local poison control center immediately. Symptoms may include restlessness, tremor, rapid breathing, confusion, irregular heartbeat, or seizures. Supportive care and monitoring are essential. (2)
Side effects
Side effects and their urgency vary; report severe, persistent, or concerning symptoms to a healthcare professional.
Dizziness
Incidence: Reported in the clinician-authored database; frequency not established
Insomnia
Incidence: Reported in the clinician-authored database; frequency not established
Constipation
Incidence: Reported in the clinician-authored database; frequency not established
Dry mouth
Incidence: Reported in the clinician-authored database; frequency not established
Paresthesia
Incidence: Reported in the clinician-authored database; frequency not established
Cognitive impairment
Incidence: Reported in the clinician-authored database; frequency not established
Increased heart rate
Incidence: Reported in the clinician-authored database; frequency not established
Suicidal thoughts
Incidence: Reported in the clinician-authored database; frequency not established
Serious warnings
US FDA BOXED WARNING — Fetal toxicity — serious
Symptoms: US FDA BOXED WARNING — Fetal toxicity: Qsymia can cause fetal harm, including oral clefts (cleft lip/palate) when a fetus is exposed in the first trimester. Exclude pregnancy before starting and monthly during treatment; females of reproductive potential must use effective contraception consistently. If pregnancy occurs, contact your prescriber immediately — Qsymia is typically stopped right away in this situation on your prescriber's direction.
Action: Follow the urgency stated and seek prompt or emergency care when indicated. (2)
Contraindications recorded in the clinician database — serious
Symptoms: Contraindications recorded in the clinician database: Contraindications: Pregnancy, glaucoma, hyperthyroidism, recent or current MAOI use, hypersensitivity to components. Use caution in patients with depression, kidney stones, metabolic acidosis, cardiovascular disease, or history of drug abuse. Monitor for mood changes, cognitive impairment, and metabolic disturbances.
Action: Follow the urgency stated and seek prompt or emergency care when indicated. (2)
May increase risk of suicidal thoughts or behavior (a class warning for antiepileptic drugs, including topiramate) — seek prompt medical help for new or worsening depression, anxiety, or suicidal thinking — serious
Symptoms: May increase risk of suicidal thoughts or behavior (a class warning for antiepileptic drugs, including topiramate) — seek prompt medical help for new or worsening depression, anxiety, or suicidal thinking. Can cause metabolic acidosis and increase the risk of kidney stones. May increase heart rate. Sudden discontinuation may precipitate seizures, especially in patients with a seizure disorder, even if Qsymia is not being used to treat seizures.
Action: Follow the urgency stated and seek prompt or emergency care when indicated. (2)
Interactions
| Medicine or test | Effect | Action |
|---|---|---|
| Recorded interactions | Qsymia can interact with other medications, including certain antidepressants, antiepileptics, oral contraceptives, and diuretics. Combining with MAOIs can cause dangerous increases in blood pressure. Inform your healthcare provider of all medications and supplements you are taking. | (1) |
Pregnancy, breastfeeding, kidney/liver function, age
Pregnancy
US FDA BOXED WARNING applies: Qsymia can cause fetal harm, including oral clefts, when used in the first trimester. Pregnancy must be excluded before starting treatment and monthly thereafter, and females of reproductive potential should use effective contraception consistently while taking Qsymia. If pregnancy occurs, contact your prescriber immediately for guidance — Qsymia is typically stopped right away in this situation on your prescriber's direction. (2)
Breastfeeding
The FDA label reviewed for this page states there is no information on the presence of phentermine or topiramate in human milk; topiramate is known to pass into human milk based on published lactation data for topiramate alone. Because of the potential for serious adverse reactions in a nursing infant, a decision should be made whether to discontinue breastfeeding or discontinue Qsymia, considering the mother's need for treatment. (2)
Children
Frequency: Not applicable.. Weight Based: Not recommended for pediatric use.. Max Daily Dose: Not applicable.. Max Single Dose: Not applicable.. Age Restrictions: Safety not established in children. (2)
Renal_impairment
Per the FDA label reviewed for this page: renal impairment — the same dosage as normal renal function applies for mild impairment (CrCl 50 to <80 mL/min); for moderate or severe renal impairment, the maximum recommended dose is 7.5 mg/46 mg once daily, and Qsymia should be avoided in end-stage renal disease requiring dialysis. Hepatic impairment — the normal-function dosage applies for mild impairment (Child-Pugh 5-6); for moderate impairment (Child-Pugh 7-9) the maximum recommended dose is 7.5 mg/46 mg once daily, and Qsymia should be avoided in severe hepatic impairment (Child-Pugh 10-15). (2)
Hepatic_impairment
Per the FDA label reviewed for this page: renal impairment — the same dosage as normal renal function applies for mild impairment (CrCl 50 to <80 mL/min); for moderate or severe renal impairment, the maximum recommended dose is 7.5 mg/46 mg once daily, and Qsymia should be avoided in end-stage renal disease requiring dialysis. Hepatic impairment — the normal-function dosage applies for mild impairment (Child-Pugh 5-6); for moderate impairment (Child-Pugh 7-9) the maximum recommended dose is 7.5 mg/46 mg once daily, and Qsymia should be avoided in severe hepatic impairment (Child-Pugh 10-15). (2)
Monitoring
(2)Storage
Per the FDA label, store Qsymia extended-release capsules at 20-25 degrees C (68-77 degrees F), with excursions permitted to 15-30 degrees C (59-86 degrees F); keep the container tightly closed and out of reach of children.
Professional information
Clinician-facing context only. This section does not replace current product labeling.
General
Indication: Chronic weight management
Dose summary: Initial dose is 3.75 mg phentermine/23 mg topiramate once daily for 14 days, then increase to 7.5 mg phentermine/46 mg topiramate once daily.
Renal context: Per the FDA label: mild renal impairment (CrCl 50 to <80 mL/min) uses the standard dosage. Moderate or severe renal impairment: do not exceed 7.5 mg phentermine/46 mg topiramate once daily. Avoid Qsymia in patients with end-stage renal disease on dialysis. (1) (2)
Frequently asked questions
How long does it take to see results with Qsymia?
Most people begin to see weight loss within the first 12 weeks of treatment when combined with diet and exercise. If you do not lose at least 3% of your body weight after 12 weeks, your doctor may adjust your dose or discontinue the medication.
Can I take Qsymia if I am pregnant or planning to become pregnant?
No. Qsymia can cause birth defects and should not be used during pregnancy or if you are planning to become pregnant. Use effective contraception while taking Qsymia.
Is Qsymia habit-forming?
Phentermine, one of the components, is a stimulant and may have potential for abuse or dependence. Take Qsymia only as prescribed and do not share it with others.
What should I do if I experience mood changes while taking Qsymia?
Contact your healthcare provider immediately if you notice new or worsening mood changes, depression, anxiety, or suicidal thoughts.
Can I stop Qsymia suddenly?
Do not stop Qsymia suddenly, especially if you have a history of seizures. Your doctor will guide you on how to safely discontinue the medication.
Does Qsymia interact with birth control pills?
Qsymia may reduce the effectiveness of some birth control pills and increase the risk of irregular bleeding. Discuss contraception options with your healthcare provider.
Is Qsymia covered by insurance or the PBS in Australia?
Qsymia may not be covered by all insurance plans or the Pharmaceutical Benefits Scheme (PBS) in Australia. Check with your insurer or the PBS for current coverage details.
What happens if I take too much Qsymia (Phentermine + Topiramate)?
Taking too much Qsymia can lead to serious side effects such as seizures, severe dizziness, rapid heartbeat, and confusion. If you suspect an overdose, seek immediate emergency medical attention. Do not attempt to self-treat. Prompt professional help is crucial to manage potential complications and ensure your safety.
Can I drink alcohol while taking Qsymia (Phentermine + Topiramate)?
It is generally advised to avoid or limit alcohol consumption while taking Qsymia. Alcohol can intensify certain side effects of phentermine and topiramate, such as dizziness, drowsiness, and impaired coordination. This combination can also increase the risk of seizures. Always discuss alcohol use with your healthcare provider.
Is Qsymia (Phentermine + Topiramate) safe during pregnancy?
Qsymia is not recommended during pregnancy due to potential risks to the fetus. It is classified as Pregnancy Category X, meaning studies have shown fetal abnormalities or risks that outweigh any potential benefits. It is crucial to consult your doctor immediately if you are pregnant or planning to become pregnant while taking Qsymia.
What is the mechanism of action of Phentermine and Topiramate?
Phentermine is a sympathomimetic amine that stimulates the release of norepinephrine in the hypothalamus, suppressing appetite. Topiramate is an anticonvulsant that promotes weight loss through modulation of voltage-gated ion channels, enhancement of GABA activity, inhibition of AMPA/kainate glutamate receptors, and inhibition of carbonic anhydrase. The combination results in synergistic appetite suppression and enhanced satiety. (2)
What is the generic name of Phentermine And Topiramate?
The generic name is Phentermine and Topiramate. It is sold under brand names including Slimtop, Qsymia, Phentop.
What class of drug is Phentermine and Topiramate?
Phentermine And Topiramate is classed as: Anorexiant; Anticonvulsant Combination; Weight Management Agent.
References
- Not providedNot provided in research notes · Not provided · accessed 2026-08-07 · source 1
- Qsymia (phentermine / topiramate) prescribing informationMedGuideGlobal · Not specified · accessed 2026-08-07 · source 2
- PHENTERMINE AND TOPIRAMATE EXTENDED-RELEASE CAPSULE [DR.REDDYS LABORATORIES INC] — US prescribing information (DailyMed SPL)U.S. National Library of Medicine (DailyMed) · US · accessed 2026-08-14 · source 3
- Phentermine and Topiramate — patient drug information (MedlinePlus)U.S. National Library of Medicine (MedlinePlus) · US · accessed 2026-08-14 · source 4
- Phentermine and Topiramate Extended-Release — FDA approval record (Drugs@FDA ANDA208175)U.S. Food and Drug Administration · US · accessed 2026-08-14 · source 5
- Phentermine and Topiramate — RxNorm normalized drug concept (RXCUI 1302826)U.S. National Library of Medicine (RxNorm) · US · accessed 2026-08-14 · source 6
Brand names by country
Single-ingredient Phentermine and Topiramate names are shown separately by country. Product availability, strengths, and supply rules can change; combination products are not included here.
Priority countries
United States
- Qsymia