Phentermine/topiramate

Phentermine/topiramate

Combination of
Phentermine	appetite suppressant/stimulant of the amphetamine and phenethylamine class
Topiramate	anticonvulsant
Clinical data
Pregnancy cat.	?
Legal status	experimental, yet has been submitted to the FDA for approval
Identifiers
ATC code	None
Y (what is this?)  (verify)

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, 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.

On February 22, 2012, FDA advisors voted 20:2 to recommend that the FDA adopt phentermine/topiramate as an obesity treatment.^[3] Final approval is expected later in 2012, with recommendations for post-market monitoring for cardiovascular risk and an indication against use by pregnant women.^[3]

Safety and effectiveness

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.^[4] The following doses of phentermine IR and topiramate CR were used in Phase 3 testing:

• Full strength formula: 15 mg of phentermine IR (instant-release) and 92 mg of topiramate CR (controlled-release)
• 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 were dry mouth, a tingling in the fingers and toes and constipation.^[5]

Approval history

On December 28, 2009 a new drug application (NDA) was submitted to the FDA for approval^[6] and on March 1, 2010, Vivus announced that the agency accepted the NDA.^[7]

FDA approval was declined in October 2010 due to concerns about dangerous side effects, including suicidal thoughts, heart palpitations, memory lapses and birth defects.^[8]

In January 2011, the Food and Drug Administration expressed concerns about the potential for Qnexa to cause birth defects and asked Vivus to examine this possibility before the drug can be approved.^[9]

Patents and other indications

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]

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.^[11]

Further research data released indicates that Qnexa lowers blood pressure. Dr. Suzanne Oparil of the University of Alabama at Birmingham 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.^[12]

References