Pharmacokinetics of diltiazem in patients with liver cirrhosis.

The pharmacokinetics of diltiazem (DTZ) was investigated in seven control subjects with normal liver function and in seven patients with liver cirrhosis. After long-term oral administration of diltiazem, 30 or 60 mg thrice daily, serum levels of DTZ and its active metabolites, deacetyl DTZ (DAD) and N-demethyl DTZ (DMD), were determined by high performance liquid chromatography. The mean peak serum concentrations (nmol/L) in control patients were 280 for DTZ, 58 for DAD and 101 for DMD. In cirrhotic patients, the serum DTZ tended to increase and the DAD increased (p less than 0.05), while the DMD decreased (p less than 0.05) compared with that of the control (335 for DTZ, 133 for DAD and 77 for DMD, nmol/L). Pharmacokinetic analysis using a one-compartment model revealed no change in the absorption, but a decrease in the elimination for cirrhotic patients (t 1/2; 5.3 to 7.2 h, p less than 0.1). The elimination rate constant correlated with some biochemical indices for hepatocyte function. These results may be explained by the impaired oxidative metabolism of diltiazem in liver cirrhosis.