Has decreased testosterone been reported as a side-effect of lamotrigine treatment?/nA 26-year-old

Fråga: Has decreased testosterone been reported as a side-effect of lamotrigine treatment?

A 26-year-old man with epilepsy has been treated with lamotrigine for two years. He experiences decreased libido and has a low level of unbound testosterone (4.5 nmol/L, reference value 6.3 16 nmol/L), and also a low level of sex hormone-binding globulin. He has no other known diseases or medications.

Sammanfattning: We have found no support in the literature that lamotrigine should cause a decrease in testosterone levels or of the sexual function.

Svar: It has been suggested that sexual dysfunction is common in patients with epilepsy, and that the etiology is probably multifactorial, involving neurological, endocrine, psychosocial and pharmacological causes (1). Enzyme inducing antiepileptic drugs, such as carbamazepine and fenytoin, are known to increase the metabolism of sex hormones, leading to an increased risk of sexual dysfunction (2, 3). Lamotrigine has in several studies been shown not to affect the levels of sex hormones or sexual function (2-5). On the contrary, there are a few case reports in the literature describing hypersexuality or improved sexual function after starting lamotrigine therapy (6, 7). Finally, in the Swedish register of adverse drug reactions, there is one report (among a total of 338) concerning impotence in a 57-year-old man after a dose increase from 200 mg to 400 mg daily of lamotrigine. No dechallenge was performed and the report was evaluated as unclassifiable (8).