Qsymia capsule is a combination oral product comprised of immediate-release phentermine hydrochloride (as the free base) and extended-release topiramate. Qsymia contains phentermine hydrochloride, a sympathomimetic amine anorectic and topiramate, a sulfamate-substituted monosaccharide related to fructose antiepileptic drug.

Phentermine Hydrochloride

The chemical name of phentermine hydrochloride is α,α-dimethylphenethylamine hydrochloride. The molecular formula is C₁₀H₁₅N • HCl and its molecular weight is 185.7 (hydrochloride salt) or 149.2 (free base). Phentermine hydrochloride is a white, odorless, hygroscopic, crystalline powder that is soluble in water, methanol and ethanol. Its structural formula is:

Topiramate

Topiramate is 2,3:4,5-di-O-isopropylidene-β-D-fructopyranose sulfamate. The molecular formula is C₁₂H₂₁NO₈S and its molecular weight is 339.4. Topiramate is a white to off-white crystalline powder with a bitter taste. It is freely soluble in methanol and acetone, sparingly soluble in pH 9 to pH 12 aqueous solutions and slightly soluble in pH 1 to pH 8 aqueous solutions. Its structural formula is:

Qsymia

Qsymia is available in four dosage strengths:

• Qsymia 3.75 mg/23mg (phentermine 3.75 mg and topiramate 23 mg extended-release) capsules;
• Qsymia 7.5 mg/46 mg (phentermine 7.5 mg and topiramate 46 mg extended-release) capsules;
• Qsymia 11.25 mg/69 mg (phentermine 11.25 mg and topiramate 69 mg extended-release) capsules;
• Qsymia 15 mg/92 mg (phentermine 15 mg and topiramate 92 mg extended-release) capsules.

Each capsule contains the following inactive ingredients: methylcellulose, sucrose, starch, microcrystalline cellulose, ethylcellulose, povidone, gelatin, talc, titanium dioxide, FD&C Blue #1, FD&C Red #3, FD&C Yellow #5 and #6, and pharmaceutical black and white inks.

Last reviewed on RxList: 4/8/2013
This monograph has been modified to include the generic and brand name in many instances.