NEW YORK (Reuters Health) – A controlled release formulation of topiramate is effective adjunctive therapy for weight loss in obese type 2 diabetics treated with diet and exercise alone or in combination with metformin, researchers report in the June issue of Diabetes Care. However, the new formulation appears to do little to curb psychiatric and other adverse effects of topiramate.
Dr. Julio Rosenstock of Dallas Diabetes and Endocrine Center, Texas and colleagues note that topiramate is used in many countries for the treatment of seizure disorders and the prophylaxis of migraines. The agent is also known to induce significant weight loss.
The controlled release formulation was developed to allow once-daily dosing and to improve tolerability. To assess the effectiveness of this approach in weight loss, the researchers conducted a randomized placebo-controlled trial in overweight or obese diabetics.
In the 111 patients whose results were analyzed following 16 weeks of treatment, the topiramate group lost 6.0 kg, 5.8% of their baseline body weight. The corresponding figures in the placebo group were 2.5 kg and 2.3%.
In the topiramate group, hemoglobin A1C improved from 7.6% to 6.7%, significantly better than the drop from 7.4% to 7.1% seen in the placebo group. Topiramate also significantly reduced blood pressure and urinary albumin excretion.
However, the researchers note that there were substantially more CNS and psychiatric adverse events in patients treated with topiramate. Such findings were similar to those previously reported.
For example, 43% of topiramate patients experienced central and peripheral nervous system disorders, compared to 21% of placebo patients. For psychiatric disorders, the figures were 33% and 11%.
These results, the investigators say, "indicate that a controlled-release formulation does not provide tolerability advantages over immediate-release formulation."
The propensity to provoke such adverse events, the team concludes, "makes it unsuitable for the treatment of obesity and diabetes."