Tolerance to the anticonvulsant effect of clonazepam in mice: no concurrent change in plasma concentration

Clonazepam was administered for 10 or more days on three different dose regimens (0.5, 0.25 and 0.08 mg kg-1 twice daily) to mice given pentetrazol by slow intravenous infusion. Plasma concentrations of clonazepam were assayed by high performance liquid chromatography. Tolerance developed to the anticonvulsant effect of clonazepam at all doses but was incomplete and could be overcome by increasing the dose. With the 0.5 and 0.25 mg kg-1 regimens there was no significant change in the drug plasma concentrations during development of tolerance; on the lowest dose, levels were below the limits of accurate detection. Anticonvulsant tolerance does not seem to be the result of a disturbance in clonazepam metabolism.