Phentermine and Topiramate for Weight Loss: Are They Safe and Effective?

dwnrbnsn's picture

Most prescription obesity drugs have not proven to be effective for long-term weight control. Many people who use them eventually gain the weight back, and they run the risk of serious side-effects while they’re on them.

A prescription drug combination made up of Phentermine and Fenfluramine, known as Phen-Fen, was removed from the market after several people developed valvular heart problems while using them. Fortunately, using Phentermine alone doesn’t appear to cause heart problems.

Now, researchers are looking at a combination of Phentermine and a migraine drug called Topiramate for weight loss. Does it work – and is it safe?

Topiramate and Phentermine for Weight Loss: Does It Work?

According to a study published in the journal Lancet, combining Phentermine with Topiramate significantly boosted weight loss in a group of 2,487 obese people. When these participants took a once-a-day dose combination of these two medications, they lost considerably more weight than the placebo group.

At the lower dose used in the study, participants lost 7.8% of their body weight vs. 1.2 percent for the placebo. The higher dose group lost almost 10% of their body weight.

What about Side-Effects of Phentermine and Topiramate for Weight Loss?

Side-effects are always a concern with any type of weight loss medication. In this study, side-effects were greater in those taking the higher dose of these two medications.

Common side-effects included dizziness, dry mouth, difficulty sleeping, sensory changes, depression, constipation and distorted taste perception. There’s another concern. Topiramate has been linked with birth defects in women who use it during pregnancy.

There were benefits other than weight loss in people who took this drug combination. People using this drug mixture lowered their blood pressure, cholesterol, and triglyceride levels. Diabetics taking it had better blood sugar control, and some participants were able to get off of their diabetes medications completely. And there was another plus. Fewer people than expected developed type 2 diabetes during the year-long study.

How Do They Work?

Phentermine works by altering levels of brain chemicals called neurotransmitters that affect appetite. No one knows exactly how Topiramate stimulates weight loss, but people on this medication have less desire to eat.

Topiramate and Phentermine for Weight Loss: The Bottom Line?

This prescription obesity drug combination shows promise, but it’s best reserved for obese people at high risk for health problems due to their weight, and who have repeatedly failed diet and exercise programs. All prescription medications carry risks, and the benefits of the drugs must be greater than those risks. There simply have not been enough studies to determine how using these drugs together affects health long-term.

For very obese people who are considering bariatric surgery, this medication combination may be worth a try under close supervision – but it’s better to avoid prescription obesity drugs for weight loss if at all possible.


Dawn Robinson is an award winning freelance journalist who has been published in several established web news outlets.  She can be found at Blogese.

Dawn graduated from Western Governor's University in 2011 with a degree in Marketing Management, and is currently attending Harvard University to obtain her Master's degree in Journalism.

Would you try a weight loss medication to lose weight?

Post new comment

The content of this field is kept private and will not be shown publicly.

Disclosure: We review and test many products on this site. Nobody pays us to review their product. However, if you end up purchasing one of these products we sometimes receive a small fee from the merchant. This helps to keep the site maintained and running.

User login

Theme provided by Danang Probo Sayekti on Hostgator