Herzog AG et al. (2005) Differential effects of antiepileptic drugs on sexual function and hormones in men with epilepsy. Neurology 65: 1016–1020

Men with epilepsy often suffer from low sexual drive and potency. A recently published study suggests that enzyme-inducing antiepileptic drugs (AEDs) could exacerbate this problem by causing serum estradiol levels to rise, leading to reduced testosterone synthesis and impaired sexual function. Non-enzyme-inducing AEDs, on the other hand, could help prevent these effects.

Herzog et al. measured various indicators of sexual function and reproductive hormones in four groups of men with localization-related epilepsy (25 taking the non-enzyme-inducing AED lamotrigine, 25 taking carbamazepine and 25 phenytoin—both enzyme-inducing AEDs—and 10 'untreated' individuals who had taken no AED for at least 6 months before analysis) and 25 nonepileptic controls. All men were aged between 18 and 50 years. A high proportion of men with epilepsy scored below the range of results seen in the control group on various indicators of sexual function. Lamotrigine treatment, however, was associated with levels of sexual function, bioactive testosterone and gonadal efficiency comparable to those of controls and untreated epileptics, and significantly better than those in patients on carbamazepine or phenytoin (P ≤0.05). Lamotrigine also produced a much smaller decline in bioactive testosterone with age than did the non-enzyme-inducing AEDs.

The authors note that the lower-than-normal bioactive testosterone levels in untreated epileptics could be due to their previous enzyme-inducing AED treatment rather than to epilepsy itself. In addition, some AEDs might have direct toxic effects on testicular function. The relationship between low sexual function scores, low bioactive testosterone levels and AED use requires further study.