Metabolic efficiency of the liver in patients with breast cancer as determined by pharmacokinetics of phenazone

: Phenazone pharmacokinetics was determined in 24 healthy women and in 39 women with breast cancer; in the latter before and after antineoplastic treatment. The mean phenazone half-life time (t0.5) was significantly shorter in patients with breast cancer (8.880 +/- 2.5585 h) than in healthy persons (12.024 +/- 3.8486 h, P less than 0.001). Mean elimination rate constant (K, 0.063 +/- 0.0197 h-1) and mean metabolic clearance rate (MCR, 54.968 +/- 20.3476 ml/min) differed statistically (P less than 0.01) from the same parameters in control group, where K was 0.063 +/- 0.0197 h-1, MCR was 41.832 +/- 14.7153 ml/min. In patients receiving antineoplastic drugs, pharmacokinetic parameters of phenazone did not differ significantly in comparison with the initial values. Our results obtained with phenazone as a model substance suggest that in breast cancer elimination of other drugs metabolized by the pathway similar to phenazone also may be changed. This should be considered in selection of their dosage.