Fat Loss Biology
Qnexa - Phentermine Structure

Qnexa is coming, regardless of its prior rejection by the FDA due to safety concerns. It is another example of the new mixed drug combinations – in this case phentermine and topiramate – being touted as diet pills. Results are good, side effects are not.

Qnexa – More Phentermine

Qnexa - Phentermine and Topiramate Structures

Phentermine has a chemical structure that resembles a class of neurotransmitters (brain and nerve chemical signals) that influences hundreds of nerve responses. The synthetic group called amphetamines, to which phentermine belongs, is a good example of artificial neurotransmitters that excite brain and nerve responses beyond normal.

Phentermine is not a particularly impressive weight loss drug by itself (see: Phentermine Reviews – Avoid It).

What about topiramate (Topamax)? It has a long history of use as an anti-convulsant and treatment for epilepsy. This history provides a thorough survey of potential side effects, expressed as percent incidence here:

  • paresthesia (numbness & tingling) (23.7%)
  • upper respiratory tract infection (17.5%)
  • diarrhea (16.8%)
  • nausea (15.4%)
  • anorexia (loss of appetite) (13.3%)
  • memory problems (11.2%)

The side-effects most frequently leading to discontinuation of therapy with topiramate have been:

  • psychomotor slowing (4.1%)
  • memory problems (3.3%)
  • fatigue (3.3%)
  • confusion (3.2%)
  • somnolence (3.2%)

One of the more recent, and scarier, developments regarding topiramate is its association with a statistically significant increase in suicidality and “suicidal thoughts or actions” in about 1 in 500 people who use it.

Qnexa Weight Loss Results

Clinical studies show Qnexa to be one of the better prescription diet pills based on results alone. The manufacturer’s phase 3 study, over a 56-week period, yielded an average of 14.7 percent weight loss (37 lbs) by obese patients.

Qnexa Approval Status

This is what got my attention in a big headline article in my local newspaper recently: Weight Loss Pill May Get Approval. The article stated that the FDA rejected the drug because it was associated with too many dangerous side effects, including suicidal thoughts, heart palpitations, memory lapses and birth defects.

In spite of the earlier rejection, On February 22, 2012, FDA advisors voted 20-2 to recommend that the FDA adopt Qnexa as an obesity treatment. Hmm.

What is going on here? Business as usual. As I’ve explained before, drug companies have invested a tremendous amount of money into the development of new drugs. They will do anything they can to capitalize on ‘collateral use’ of already approved drugs — in this case combining phentermine and topiramate into a new formula for weight loss.

From what I’ve found out about this new drug, it will be approved, probably this year. I’m not too thrilled about it, though. The weight loss results, as good as they are, do not justify the risk of side effects.

Updating Qnexa diet pills status,

Dr. D

2 Comments so far »

  1. by Brendamitch


    I have a binge eating disorder and I took Topamax in desperation and as a last resort. Please do not judge me for taking this as anyone who suffers from this monster is desperate to stop it. I lasted 5 days before I quit. I was spaced out and groggy, too tired to exercise and I was still on a lower dose. I guess it was going to make me so dopey and sick that I wouldn’t eat and that is not how I want to live. I do not recommend EOD for binge eaters because eventually the normal days tend to become binge days. I lasted on EOD for a month and had to give up as bingeing was getting worse. Most conventional advice to binge eaters is to eat 3 meals and 2 snacks per day and this doesn’t work. If I eat breakfast or regular meals then I am hungry all day. The best tactic that seems to work for me is a one meal per day, later in the day so as to delay eating as long as possible and supplementing with chromium GTF and 5htp. Also sleep is important, a night of insomina almost guarantees a binge the next day.

  2. by Dr. Dennis Clark


    Thank you for your input. I am glad to see that you have been able to figure a few things out on your own. The one meal per day strategy works for many people in a number of ways. I had not heard about how it helps with binge eating. Some research on the benefits of alternate day fasting may also be a nugget for you. See my post today: Finding Truths About Intermittent Fasting.

    All the best,

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