Topiramate (Topamax) and Weight Loss

There is good evidence that Topiramate promotes weight loss and suppresses the appetite 1-5. However, Ortho-McNeil prematurely stopped a large phase III program for Topamax as a weight loss drug because of emotional and cognitive side effects. So far it is not licensed for obesity.

Nevertheless, the research data shows that Topiramate may be useful to manage excess weight. In most studies, about 60-70% of people experienced weight loss1-5. Topamax may promote weight reduction of up to 15-18% of the baseline weight.

Weight loss on topiramate has been reported in people suffering from bipolar disorder who gained weight due to psychotropics3. The small study found that Topamax may be effective for SSRI-induced weight gain4. Also, Topamax may help to maintain weight following a low calorie diet5.

In the three-month study, those on topiramate lost an average of 8.8 pounds (4 kg), they found.

How does Topamax make you lose weight?

The exact mechanism of action regarding weight loss is still uncertain. It seems to be related to: increase of energy expenditure, reduction in the activity of salivary enzymes responsible for taste, reduction in leptin and corticosteroid concentrations, and reduction of glucose and insulin levels.

Many people taking this drug report certain foods taste different. With altered taste sensations you experience less pleasure from eating.

Topamax dosage

The dosage of topiramate given to participants in obesity studies ranges from 25 mg to 400 mg, taken in two divides doses.

Topamax and Phentermine combination for weight loss

Qsymia (formerly Qnexa), approved in July 2012, is a combination of phentermine, an appetite suppressant and stimulant, and topiramate. The drug is indicated as an addition to a reduced-calorie diet and exercise for chronic weight management.

Qsymia is approved for use in adults with body mass index (BMI):

  • 30 or greater (obese)
  • 27 or greater (overweight) who have at least one weight-related condition such as high blood pressure, type 2 diabetes, or high cholesterol.

Qsymia approval was based on the results of two, 1-year studies involving nearly 4,000 obese and overweight people, comparing phentermine-topiramate to placebo6, 7. People who took phentermine-topiramate for one year lost 3.5 to 9.4 kg more than those who took a placebo. An about 62% lost at least 5% of their baseline body weight, compared with about 20% of those who took placebo.

Safety concerns

Qsymia was initially denied FDA approval in 2010 because of potential serious side effects, including heart palpitations and birth defects (cleft lip or palate) if taken by pregnant women.


Many users report loss of weight:

See also


  • 1. McElroy SL, Frye MA, Altshuler LL. Sibutramine versus topiramate for weight gain in overweight or obese patients with bipolar disorders. Bipolar Disord. 2007 Jun;9(4):426-34.
  • 2. Leombruni P, Lavagnino L, Fassino S. Topiramate in obese patients with binge eating disorder. Neuropsychiatr Dis Treat. 2009;5:385-92. PubMed
  • 3. Tremblay A, Chaput JP. Topiramate and energy balance in obese men. Eur J Clin Pharmacol. 2007 Feb;63(2):123-34.
  • 4. Van Ameringen M, Mancini C, Pipe B, Campbell M, Oakman J. J Clin Psychiatry. 2002 Nov;63(11):981-4.
  • 5. Astrup A, Caterson I, Zelissen P, Guy-Grand B, Carruba M, Levy B, Sun X, Fitchet M. Topiramate: long term maintenance of weight loss. Obes Res. 2004 Oct;12(10):1658-69. PubMed
  • 6. Allison DB, Gadde KM, Garvey WT, Peterson CA, Schwiers ML, Najarian T, Tam PY, Troupin B, Day WW. Controlled-release phentermine/topiramate in severely obese adults: a randomized controlled trial (EQUIP). Obesity (Silver Spring). 2012 Feb;20(2):330-42. PubMed
  • 7. Gadde KM, Allison DB, Ryan DH, Peterson CA, Troupin B, Schwiers ML, Day WW. Effects of low-dose, controlled-release, phentermine plus topiramate combination on weight and associated comorbidities in overweight and obese adults (CONQUER). Lancet. 2011 Apr 16;377(9774):1341-52. PubMed

Author: OriginalDrugs Team
Last reviewed: February, 2015

Good to know

  • The combination phentermine/topiramate is marketed as Qsymia by Vivus, not Qnexa, the original proposed trade name.
  • Qsymia is the second medication approved for weight loss in last 13 years. In June, the FDA approved Belviq (lorcaserin), for the same indication.