Phentermine/topiramate

Phentermine/topiramate
Combination of
Phentermine	appetite suppressant/stimulant of the amphetamine and phenethylamine class
Topiramate	anticonvulsant
Legal status
Legal status	experimental, yet has been submitted to the FDA for approval;
Identifiers
ATC code	none

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The combination of the drugs phentermine and topiramate (trade name Qnexa) is an investigational medication for the treatment of obesity and related conditions such as type 2 diabetes and has been found to lower blood pressure and cholesterol.^[1] Qnexa is being developed by Vivus, Inc. (NASDAQ: VVUS ), a California pharmaceutical company.^[2] Phentermine is an appetite suppressant and stimulant of the amphetamine and phenethylamine class. Topiramate is an anticonvulsant that has weight loss side effects.

Clinical studies have shown weight loss under treatment with Qnexa. The phase 3, 56-week EQUIP study showed that the average weight loss of 14.7% (37 lbs) was achieved by obese patients treated with Qnexa.^[3] The following doses of Phentermine IR and Topiramate CR where used in Phase 3 testing:

Full strength formula: 15 mg of Phentermine IR and 92 mg of Topiramate CR
Mid strength formula: 7.5 mg Phentermine IR and 46 mg Topiramate CR
Low strength formula: 3.75 mg Phentermine IR and 23 mg Topiramate CR

The main side effects reported during testing phases where: dry mouth, a tingling in the fingers and toes, and constipation.^[4] On December 28, 2009 a new drug application (NDA) was submitted to the FDA for approval^[5] and on March 1, 2010, Vivus announced that the agency accepted the NDA.^[6] The target date for the FDA to complete its review of the Qnexa NDA is October 28, 2010.^[7] The FDA's Endocrinologic and Metabolic Drugs Advisory Committee is tentatively scheduled to review Vivus' Qnexa on July 15, 2010. It is expected that this may provide an indication on whether it is approved or not.^[8]

Qnexa is also in phase 2 clinical development for the treatment of type 2 diabetes and obstructive sleep apnea (OSA). A phase 2 safety and efficacy study evaluating Qnexa in patients with OSA showed that patients who took Qnexa had a 69 percent reduction in sleep apnea events and lost more weight than those who took placebo.^[9]

Vivus currently has four U.S. patents covering Qnexa. These patents are related to the product and methods of using the drug in various therapeutic applications.^[10]

Further research data released indicates that Qnexa lowers blood pressure. Dr. Suzanne Oparil of the University of Alabama at Birminham stated “The higher the dose, the more weight loss and the more blood pressure went down” presented at the American Society of Hypertension’s 25th annual meeting in New York.^[11]