Albendazole is considered the drug of choice for neurocysticercosis. It is frequently used in combination with dexamethasone to prevent the acute inflammatory reaction due to cysticercal death. It has been reported that dexamethasone increases the plasma level of albendazole sulfoxide, the active metabolite of albendazole. The pharmacokinetic interaction of albendazole sulfoxide with dexamethasone, associated or not with cimetidine, was investigated in 24 patients with active intraparenchymal brain cysticercosis. Eight of these patients received albendazole alone, eight received it in combination with dexamethasone, and eight received it in combination with both dexamethasone and cimetidine. The pharmacokinetic parameters maximum plasma concentration, time to maximum plasma concentration, absorption half-life, and absorption rate constant did not differ between groups, suggesting that the formation of albendazole sulfoxide was not altered by the administration of dexamethasone, combined or not with cimetidine. There were significant differences, however, in the parameters plasma concentration-time curve, oral clearance, elimination half-life, and elimination rate constant, suggesting that dexamethasone, combined or not with cimetidine, decreases the rate of elimination of albendazole sulfoxide.