Qnexa is made from two old drugs. One of these drugs was contained in the infamous Wyeth diet pill, Fen-Phen. The other drug is Johnson & Johnson’s Topamax, or topiramate, originally developed for migraines and epileptic seizures, which also has a history of side effects. Vivus, the manufacturer of Qnexa, anticipates filing for new drug authorization for Qnexa by the end of 2009. Most analysts believe that the FDA could approve Qnexa by the end of 2010. While the medication is already in stage III trials as a diet pill, Vivus also hope to receive FDA approval to market it as a diabetes medication. Diabetes and obesity can be closely linked and medical experts have warned that as obesity increases worldwide, so too will the numbers of people developing type 2 diabetes.
How does Qnexa work?
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. As such, Qnexa appears to induce significantly greater weight loss than either individual compound.
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, which acts via a different mechanism. 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. Originally an epilepsy drug, topiramate is also used to help prevent migraine headaches.
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 percent for full-dose Qnexa, 0.9 percent for the mid-dose and 1.8 percent for placebo patients.
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).
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 paresthesia (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 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
Clinical studies on Qnexa
Patients in the Vivus sponsored Qnexa phase 3 clinical studies were asked to reduce calorie intake by 500 a day and advised to exercise three times a week. The results to date show that Qnexa promotes weight loss.
The EQUIP study was designed to look at the effect of Qnexa on morbidly obese patients, that is, those patients with a baseline BMI of 35 or greater. In total, 1267 obese people at 93 sites in the US were tested. The average baseline BMI in the EQUIP study was 42.1. A review of results by baseline BMI show a consistent effect across a broad range of patients based on starting body weight. On an ITT-LOCF basis, the overall percent weight loss in the EQUIP study was 11% for patients on full dose Qnexa, as compared to 1.6% for the placebo group. The CONQUER study included 2,487 overweight and obese patients with high blood pressure, high cholesterol or type 2 diabetes across 93 centers in the US.
Key findings from the EQUIP (full dose) and CONQUER (half dose0 studies include:
- Average weight loss of 14.7% (37 lbs) was achieved by patients treated with Qnexa for 56 weeks in the EQUIP study
- Average weight loss of 8.4% (19 lbs) was achieved by patients treated with Qnexa for 56 weeks in the CONQUER study
- Average weight loss of 5.1% (18 lbs) was achieved by patients treated with Qnexa for 56 weeks in the low dose EQUATE study
- Significant improvements in cardiovascular, metabolic and inflammatory risk factors among patients treated with Qnexa
- FDA efficacy benchmarks for weight loss agents were exceeded at all three doses of Qnexa evaluated in the clinical studies
- Completion rates up to 69% were significantly higher than placebo at all three doses of Qnexa, indicating favorable tolerability
Qnexa conclusion
The weight loss observed with Qnexa in the EQUIP and CONQUER one-year, double-blind, randomized trials exceeds the weight loss observed for other agents reported in the scientific literature.
Reference
Press Releases from Vivus Inc. http://ir.vivus.com
Where to buy Qnexa
Qnexa not yet been approved by the FDA, but the key ingredients have been approved. Your doctor can prescribe phentermine and Topamax (topiramate), the drug combination found in Qnexa. However, the best advice is to wait for Qnexa to reach retail outlets and then take it under medical supervision.
