Long-term effectiveness and side effects of acetazolamide as an adjunct to other anticonvulsants in the treatment of refractory epilepsies

The long-term effectiveness of acetazolamide (AZA) and its side effects, especially the formation of renal calculi, were investigated in a prospective study when AZA was used as an adjunct to other antiepileptic drugs in the treatment of refractory epilepsies. The subjects comprised 37 patients aged from 1 to 17 years (mean age, 8 years and 1 month) whose seizures were hard to control with the use of two or more drugs among sodium valproate, carbamazepine and clonazepam. Thirty-two of the 37 patients were complicated with mental retardation. A daily dose of 10 mg/kg of AZA was first administered and then the dosage was increased up to 20 mg/kg based on the clinical response and side effects. The maintenance daily dosage of AZA (12.2±4.2 mg/kg) produced a steady-state plasma concentration of 6.2±4.5 μg/ml. Among the 37 patients, complete seizure control for more than 3 years was obtained in four patients. Although there were no significant differences, all of the four patients were classified as having symptomatic localization-related epilepsies. Seizures recurred in five after complete remission for at least 6 months, and six showed >50% decrease in seizure frequency for more than 6 months after the introduction of AZA. Twenty-eight patients, who were taking AZA for 10 months to 14 years (mean, 6 years and 5 months), were examined for the formation of renal calculi. None of them showed evidence of renal calculi. This study reinforces the idea that AZA may be a useful adjunct drug in selected patients with refractory symptomatic localization-related epilepsies.