New Diet Drug Qnexa Promises 10% Weight Loss - At What Price?

This week’s big news is the potential arrival of Qnexa, the first new obesity drug to head for tentative FDA approval in 13 years. (The last, Xenical, hit the market in 1999.) Of course, there’s good reason for that; numerous weight loss drugs have been found to have dangerous side effects, causing the FDA to reject them. In fact, Qnexa itself was rejected by the FDA in 2010. So what’s up now?

So far, the story’s mainly being reported as a business story. And that it certainly is; the stock of Vivus, Inc. the Mountain View-based pharmaceutical upstart that created Qnexa, jumped 98 percent today in its first day of trading after the FDA panel’s 20 to 2 vote. Given past sales figures for diet drugs, Vivus can expect to make a boatload of cash on Qnexa and shareholders will smile all the way to the bank. One analyst predicted the drug could be the “next Lipitor,” resulting in millions of prescriptions.

But what about the people taking it? How long will they be smiling?

In terms of weight loss, Qnexa will likely produce smiles. Clinical data (not yet published) showed participants lost an average of 10 percent of their body weight, according to Vivus’ claims. But as Robert Carlisle’s Mr. Gold loves to say on the TV hit Once Upon a Time, “All magic comes at a price.” What’s the price to your overall health of taking Qnexa?

Let’s start with what’s in the drug. Qnexa is actually a “cocktail,” meaning it’s a combination of two previously FDA-approved drugs, phentermine — an appetite suppressant — and topiramate, an anti-convulsant.

If you feel like you’ve heard the name phentermine before, you have - it’s the “phen” from the notorious diet drug cocktail of the 1980s, Fen-Phen, withdrawn from the market for damaging heart valves. Technically a contraction of the chemical name phenyl-tertiary-butylmine, phentermine has a similar pharmacology to amphetamine and works by suppressing appetite.

Because it works by triggering the release of catecholamines, phentermine is known to have two heart-related side effects: tachycardia (increased heart rate) and elevated blood pressure. These side effects don’t happen with the frequency and severity that they do with amphetamines, but patient complaint boards are full of people posting messages about worrisome spikes in heart rate and blood pressure and resulting heart palpitations.

Here’s how nurse Patricia Nevins describes it: “Phentermine hydrochloride affects the cardiovascular system in much the same way that fear, excitement and anger do. Essentially an amphetamine, phentermine stimulates the part of the central nervous system that regulates the heart and blood pressure. Physicians prescribe phentermine hydrochloride as part of a weight-loss program because of its ability to increase metabolism and suppress the appetite. The cardiovascular effects of phentermine can cause serious heart problems.” I couldn’t have put it any better myself, hence the quote.