Weight gain with valproate or carbamazepine--a reappraisal

The use of valproate has traditionally been held to be associated with a greater incidence of weight gain than that of other anticonvulsants. This paper presents an analysis of body weight data gathered during a randomized trial comparing valproate with carbamazepine in 260 children aged 4-15 years with newly-diagnosed epilepsy. There were more reports of weight gain as an adverse event in the valproate group than in the carbamazepine group (22 reports in 14 patients vs. nine reports in five patients). However, amongst the 211 patients (103 on valproate and 108 on carbamazepine) in whom objective weight measurements were taken during treatment, there were no differences between the treatments in percentage weight gain from baseline or incidence of excessive weight velocity. Eight patients reporting weight gain on valproate were switched to carbamazepine because of poor seizure control and/or adverse events including weight gain, but three of the four patients for whom body weight measurements were available continued to gain weight on carbamazepine. It is concluded that weight gain may be erroneously attributed to valproate treatment.