Influence of aminoglutethimide and spironolactone on the efficacy of carbamazepine and diphenylhydantoin against amygdala-kindled seizures in rats.

Antagonists of steroid receptors may interfere with seizure phenomena. The present study deals with effects of aminoglutethimide and spironolactone on the action of carbamazepine and diphenylhydantoin in amygdala-kindled rats of both genders. Co-administration of the antimineralocorticoid with carbamazepine at their ineffective doses (50 and 15 mg/kg, respectively) led to significant reduction of the seizure and afterdischarge durations. No anticonvulsant effect was observed when spironolactone was combined with diphenylhydantoin. The concomitant treatment of aminoglutethimide and carbamazepine (both drugs at their subprotective doses of 5 and 15 mg/kg, respectively) resulted in antiseizure activity in respect of all measured parameters, including the afterdischarge threshold, seizure severity, seizure duration and afterdischarge duration. The similar combination of aminoglutethimide with diphenylhydantoin (2.5 mg/kg) significantly shortened the seizure and afterdischarge durations. The antiseizure effect of tested combinations was not sex-dependent and not reversed by hydrocortisone pretreatment. Pharmacokinetic events may be involved only in the interaction between spironolactone and carbamazepine. Among various chemoconvulsants, bicuculline reversed the action of aminoglutethimide on carbamazepine and diphenylhydantoin. The effect of aminoglutethimide on diphenylhydantoin was also abolished by N-methyl-d-aspartic acid and aminophylline. In conclusion, our results suggest that doses of carbamazepine and diphenylhydantoin should be modified in epileptic patients concomitantly treated with aminoglutethimide or spironolactone.