Cimetidine-induced rise in praziquantel levels in a patient with neurocysticercosis being treated with anticonvulsants.

A patient had neurocysticercosis complicated by a seizure disorder requiring anticonvulsants; previous praziquantel therapy (50 mg/kg/day) had failed to eradicate the disease. In an attempt to inhibit cytochrome P-450 metabolism of praziquantel, cimetidine (1600 mg/day) was coadministered. Before addition of cimetidine, the maximum concentration of praziquantel was 350 ng/mL; concurrent cimetidine administration increased the maximum concentration to 826 ng/mL. The elimination half-life increased from 1.7 h without cimetidine to 3.3 h with cimetidine and the area under the curve for the 12-h sampling period rose from 754 ng.h/mL to 3050 ng.h/mL. Coadministration of cimetidine raises serum praziquantel levels and may be helpful in patients treated concomitantly with praziquantel and anticonvulsants.