Therapeutic tolerance, hemodynamic effects, and oral dose kinetics of dilazep dihydrochloride in hypertensive patients.

Abstract

The oral dose metabolism of dilazep dihydrochloride [tetrahydro-1H-1,4-diazepine-1,4(5H)-dipropanol 3,4,5-trimethoxybenzoate] was examined in six hypertensive patients receiving a single oral dose of 600 mg of dilazep (3-3.8 mg/kg BW). Blood was collected at 0.5, 1, 1.5, 2, 3, 4, 6, 8, 10, and 24 h after administration of the dose and urine was collected for three time intervals of 0-4 h, 4-10 h, and 10-24 h. Dilazep concentrations in blood and urine were determined by high-performance liquid chromatography. Dilazep decayed monoexponentially with a mean elimination rate constant of 0.27 +/- 0.13 h-1 and a mean half-life of 3.04 +/- 1.34 h. The mean tmax of absorption was 1.40 +/- 0.82 h. With maximally tolerated chronic doses, the steady-state concentration measured at 1 week was 25.6 ng/mL in a patient receiving 300 mg daily (100 mg TID) for 3 weeks, and dilazep concentration increased with the dose in others for up to a 600-mg dose daily. Dilazep did not produce any significant changes in heart rate and blood pressure after a single oral dose or during chronic dosing. There was no correlation between blood dilazep levels and the changes in heart rate and blood pressure. In three additional patients, oral dilazep dihydrochloride titrated gradually to maximally tolerated doses (900 mg daily) failed to produce significant effects on biochemical and neurohumoral measurements, and hemodynamic parameters as well as ventricular functional indices measured by radionucleide methods. Oral dilazep administration in maximally tolerated doses is devoid of effects on blood pressure and cardiac hemodynamic function.