Qnexa Side Effects

Qnexa is a proprietary drug formulation that incorporates the active ingredients from two previously approved products with proven weight loss properties – phentermine and topiramate. By combining the activity of each of these compounds in a once-daily, low-dose capsule formulation, Qnexa simultaneously targets appetite and satiety. The weight loss observed with Qnexa in the EQUIP and CONQUER clinical trials exceeded the weight loss observed for other agents reported in scientific literature. The most common side effects of Qnexa are itching, dry mouth, altered taste and constipation.

See also: Qnexa Review

Phentermine has been available for treating obesity since the 1950s and is still the most widely prescribed weight loss drug. Topiramate was approved in 1996 for treating epilepsy, and more recently as a prophylactic for migraine. The rationale behind Qnexa is to expand topiramate’s therapeutic window by using a low dose and combining it with phentermine. Topiramate works via GABA and other agonist properties and increases the sensation of fullness or satiety, while phentermine is noradrenergic and non-serotonergic, and reduces appetite.

Phentermine is released into the body immediately and helps reduce appetite. It was a major component of the recalled diet drug fen-phen, which was linked to heart and lung problems and was taken off the market ion 1997. Topiramate is time released and used in very low doses to give patients a feeling of satiety.

Side effects of Qnexa

Qnexa is claimed by the manufacturer to be well tolerated. The most common side effects are itching, dry mouth, altered taste and constipation.

Reported drug-related adverse events for depression and altered mood were 1.9% for full-dose Qnexa, 0.9% for the mid-dose and 1.8% for placebo patients.

The most common side effects reported by patients given a half-dose of Qnexa (7.5 mg of phentermine plus 46 mg of Topamax) or a full-dose of Qnexa (15 mg of phentermine plus 92 mg of Topamax) were:

• 15-20% reported a feeling of “pins and needles” on the skin versus 3% in the placebo group
• 12-18% reported dry mouth versus 0% in the placebo group
• 8-15% reported altered taste versus 0% in the placebo group
• 6-11% reported constipation versus 6 percent in the placebo group
• 0.9-1.9% reported depression and altered mood versus 1.8 percent in the placebo group

Qnexa and depression

Depression, or depressed mood adverse events of a moderate to severe nature, were less than 2% and were similar among patients in the Qnexa and placebo groups.

Qnexa and behaviour change and suicide attempts

There were no suicide attempts or suicidal behaviors, and there was no signal for suicidal ideation across all Qnexa treatment groups including the placebo. The US Food and Drug Administration (FDA) previously put out a warning that Topamax (topiramate) increases the risk of suicidal thoughts.

Qnexa discontinuation rates

Overall in clinical studies, discontinuation rates due to adverse cognitive events were low and the events were generally mild to moderate and reversible with discontinuation of treatment. There was one severe event in the treatment arm and one in the placebo arm that led to discontinuation. Discontinuation rates for these various cognitive-related events were low and all occurred at a frequency of less than 1%. This rate is considerably lower than the 3% discontinuation rate reported for Topamax (topiramate).

Qnexa ingredients

Qnexa is a propriety formulation. The key ingredients are topiramate and phentermine.

Qnexa is currently being evaluated in clinical studies at 3 different doses:

• Full strength: 92mg of topiramate/15 mg of phentermine
• Mid dose: 46mg of topiramate/7.5mg of phentermine
• Low dose: 23 mg of topiramate/3.75mg of phentermine

Reference

Press Releases from Vivus Inc. http://ir.vivus.com