Hyponatremia during carbamazepine therapy in patients with intellectual disability.

Carbamazepine is an anticonvulsant and psychotropic medication commonly used in the treatment of people with intellectual disability (ID). The incidence of hyponatremia during treatment in this population is unclear. The present study aimed to determine the prevalence of hyponatremia during carbamazepine treatment in patients with ID, and to investigate the risk factors and clinical features of this condition. The prevalence of hyponatremia was retrospectively assessed in 53 people receiving carbamazepine (subject group) and 64 people not receiving carbamazepine (control group) who lived in a residential centre for people with ID. The relationship between serum sodium level, sex, age, daily carbamazepine dose and serum carbamazepine levels was examined. The prevalence of the clinical features of hyponatremia was assessed in this population using a checklist. The prevalence of hyponatremia was 41.5% and 9.4% in the subject and control groups, respectively. The mean serum sodium level in the subject group was significantly lower than that in the control group. Hyponatremia correlates significantly with a high daily carbamazepine dose and a high serum carbamazepine level. The checklist of clinical features was not useful in detecting hyponatremia clinically. Hyponatremia is a common occurrence in this population. In the light of the uncertain significance of mild, chronic hyponatremia, the value of routine monitoring of serum electrolytes has yet to be established.