Lamictal is an anticonvulsant medication that can be used to treat seizure disorders and as a mood stabilizer in bipolar disorders. In the original clinical trials, 5% of adults with epilepsy lost weight while taking Lamictal, while between 1 and 5% of patients with Bipolar I disorder gained weight. The amount of weight gained or lost is not listed.
A study comparing the effects on weight of Lamictal, lithium, and a placebo found that some patients receiving Lamictal gained weight, some lost weight, and most remained at about the same weight -- but the weight changes weren't significant compared to the placebo group. Obese patients taking Lamictal lost an average of four pounds, while non-obese patients' weight remained essentially the same.
Another study that looked specifically at Lamictal for possible treatment of obesity found that the drug definitely caused a decrease in BMI compared to placebo. Thus, researchers feel confident placing Lamictal in the "weight neutral" category.
Bowden, Charles, MD, et al. Impact of Lamotrigine and Lithium on Weight in Obese and Nonobese Patients With Bipolar I Disorder. American Journal of Psychiatry. 163.7 (2006): 1199-1201. Web. 18 Feb 2011.
Meredith, CH. A single-center, double-blind, placebo-controlled evaluation of lamotrigine in the treatment of obesity in adults. Journal of Clinical Psychiatry (via PubMed) 67.2 (2006): 258-62. Web. 18 Feb 2011