Combination of Phentermine & Topiramate for obesity treatment......

We know that Phentermine (see structure) is  an appetite suppressant of the  amphetamine and phenethylamine class. It is approved as an appetite suppressant to help reduce weight in obese patients. Its  usually used for short-term and in combination with exercise, diet and behavioral modification. Is typically prescribed for individuals, who are at increased medical risk because of their weight and works by helping to release certain chemicals in the brain that control appetite.  

Mode of action : Phentermine, in doses clinically used, works on the hypothalamus portion of the brain to release norepinephrine, a neurotransmitter or chemical messenger that signals a fight-or-flight response, reducing hunger. Phentermine works outside the brain as well to release epinephrine or adrenaline causing fat cells to break down stored fat, but the principal basis of efficacy is hunger-reduction. At high doses, phentermine releases serotonin and dopamine as well, but such doses are never used in clinical medicine.  

Topiramate (structure below), is a known anticonvulsant agent and  also  reported  for  the  treatment   of

SSRI-  induced weight gain in anxiety disorders. However a combination   of these two drugs (Phentermine & Topiramate) has been  tried by VIVUS, Inc. and has submitted New Drug Application (NDA)   to the U.S. Food and Drug Administration (FDA) seeking approval of Qnexa (Phentermine & Topiramate combination) - its investigational drug for the treatment of obesity, including weight loss and maintenance of weight loss, in patients who are obese or overweight with co-morbidities such as hypertension, type 2 diabetes, dyslipidemia or central adiposity.

The NDA submission follows the successful completion of the phase 3 program for Qnexa, including the recently announced results from the two pivotal, year-long phase 3 studies (EQUIP and CONQUER). In these trials, patients treated with all three doses of Qnexa achieved significant percent and categorical weight loss compared to placebo and met regulatory requirements for weight loss products as defined in the current FDA Guidance for Developing Products for Weight Management. Patients treated with Qnexa also had significant dose-related improvements in a variety of secondary endpoints including reductions in cardiovascular and metabolic risk factors. Hope people with obesity, will breathe a sigh of relief in the near future....

Ref : http://ir.vivus.com/releasedetail.cfm?ReleaseID=433172