Phenazone pharmacokinetics as an index of hepatic metabolic efficiency.

Phenazone pharmacokinetics as an index of hepatic microsomal enzyme activity was studied in 31 patients with Hodgkin's disease, 11 patients with non-Hodgkin's lymphoma and 52 healthy volunteers. The mean phenazone half-life (t0.5) was significantly shorter in patients with Hodgkin's disease (8.002 +/- 2.775 h) and in patients with non-Hodgkin's lymphoma (8.775 +/- 2.440 h) than in healthy persons (11.351 +/- 3.706 h). In patients with Hodgkin's disease and in patients with non-Hodgkin's lymphoma mean elimination rate constant (Kel) (0.101 +/- 0.050 h-1; 0.086 +/- 0.028 h-1) and mean metabolic clearance rate (MCR) (70.464 +/- 50.347 ml/min; 71.621 +/- 21.448 ml/min) differed statistically significantly from the same parameters in control group, where K was 0.067 +/- 0.021 h-1 and MCR 49.361 +/- 18.167 ml/min. Treatment with antineoplastic drugs inhibited phenazone elimination. No correlations were found between the phenazone pharmacokinetics parameters and routine laboratory tests of liver function. Since many drugs are metabolized by cytochrome P-450, similar to phenazone, it is likely that their elimination in patients with Hodgkin's disease and in patients with non-Hodgkin's lymphoma will be also changed. This should be considered in selection of their dosage.