The FDA has expressed concerned regarding obesity drug Qnexa - a combination of phentermine and topiramate - and what associations there may be between long-term usage and birth defect risks, as well as its impact on the heart. The Food and Drug Administration (FDA) is reviewing Qnexa again, after turning down its submission for approval two years ago ("FDA Turns Down Weight Loss Drug Qnexa, But Makers See Short Timeline For Approval").
There is an FDA Advisory Panel (Endocrinologic and Metabolic Drugs Advisory Committee) meeting on 22 February. The Panel will look at 2-years' worth of clinical data. When Qnexa was last reviewed, the Agency only had 1-year's worth of data to look at.
The Advisory Panel consists of experts, none of whom work for the FDA. They will have to discuss and vote on whether to recommend supporting or declining the obesity drug after carrying out an overall benefit-risk assessment. The Panel's recommendation is not binding; the FDA can choose to ignore it; but this hardly ever happens. Therefore, Qnexa's future, at least this time round, depends on what happens this coming Wednesday.
When the FDA turned Qnexa down, it asked its makers Vivus Inc. for more clinical data on the medication's potential impact on major adverse cardiovascular events and birth defects.
The FDA now acknowledges that studies have demonstrated that Qnexa can help patients lose a considerable amount of weight during the initial 12 months of treatment. The Agency added that a number of participants put some of their lost weight back on during their second year. Concerns regarding birth defects and accelerated heartbeat were raised again.
Qnexa is a combination of phentermine and topiramate. Studies on topiramate have indicated that there may be a higher chance of having babies with birth defects. According to the FDA, pregnant women who are exposed to topiramate might have a higher risk of giving birth to babies with oral clefts.
At first, Vivus suggested limiting Qnexa use to adult males and females of specific age groups (non-child bearing ages). According to Vivus, the FDA responded by asking the company to come up with a plan of limited usage by pregnant women.
Qnexa consists of:
- Phetermine, chemical formula C10H15N - a psychostimulant appetite suppressor. Its pharmacology is similar to amphetamine. Medically, it is currently used to suppress appetite.
- Topiramate, chemical formula C12H21NO8S - an anti-epilepsy (anticonvulsant) medication which also increases the sensation of feeling full (of food). Psychiatrists sometimes use topiramate for bipolar disorder. It is currently being investigated for the treatment of alcoholism
Written by Christian Nordqvist