Qsymia (phentermine + topiramate ER): the 2026 GLP-1 guide

Overview

Qsymia is a fixed-dose oral combination of phentermine (a sympathomimetic appetite suppressant; Schedule IV controlled substance) and topiramate ER (an anticonvulsant that suppresses appetite as a secondary effect), FDA-approved on July 17, 2012 for chronic weight management.

It is NOT a GLP-1 agonist. Phentermine drives appetite suppression via norepinephrine/dopamine release; topiramate’s mechanism in weight loss is multifactorial (GABA modulation, kainate inhibition, carbonic anhydrase inhibition).

Clinical Efficacy

In EQUIP (severe obesity, BMI ≥ 35), Qsymia 15/92 mg produced 10.9% body weight loss at 56 weeks vs 1.6% placebo. In CONQUER (BMI 27–45 + ≥ 2 comorbidities), 15/92 mg produced 9.8% loss vs 1.2% placebo¹.

Qsymia is the highest-efficacy non-GLP-1 oral weight-loss medication available in 2026, but still produces less weight loss than oral GLP-1s (~12-16%) on average.

Dosing & Titration

Four approved capsule strengths (phentermine / topiramate, mg):

• 3.75 / 23 — starting dose, 14 days only
• 7.5 / 46 — recommended maintenance dose
• 11.25 / 69 — escalation step (14 days)
• 15 / 92 — maximum approved dose

Schedule: start at 3.75/23 mg once daily for 14 days, then increase to 7.5/46 mg. After 12 weeks at 7.5/46 mg, if weight loss is < 3% body weight, escalate to 11.25/69 mg for 14 days, then 15/92 mg. Discontinue if weight loss is < 5% after 12 weeks at the maximum dose.

Take in the morning. Evening doses raise insomnia risk substantially.

Side Effects

REMS program — pregnancy contraindication

Qsymia is distributed only through certified pharmacies under the QSYMIA REMS because of teratogenic risk: topiramate is associated with oral cleft birth defects when taken during the first trimester. Patients capable of pregnancy must use effective contraception and complete monthly pregnancy testing¹. The REMS website is qsymiarems.com.

Most common adverse reactions (Qsymia 15/92 mg vs placebo)

Contraindications

• Pregnancy (teratogenicity)
• Glaucoma
• Hyperthyroidism
• Use of MAOIs (or within 14 days of stopping one)
• Known hypersensitivity to phentermine, topiramate, or excipients; or idiosyncrasy to sympathomimetic amines

2026 Availability

Qsymia is on Part D Tier 3 with most plans but distribution is limited to REMS-certified pharmacies. Cash list price is approximately $230/month at the 15/92 mg dose.

Qsymia is NOT on the Medicare GLP-1 Bridge program — Bridge eligibility is restricted to GLP-1 receptor agonists.

For patients comparing oral weight-loss options: Qsymia at ~10% loss + REMS friction sits below Foundayo (~12-16%, no REMS, $25-149/mo) and Wegovy Tablets (~12-15%, $149/mo) but above Contrave (~5-9%) on efficacy. Qsymia is the right pick for patients who: (a) can’t access GLP-1s, (b) won’t risk GLP-1 GI side effects, and (c) can accept the REMS contraception/testing requirement.