The paper reviews both the data available in the literature and the authors' own results of long-term experimental and clinical investigations of the involvement of hepatic
monooxygenases (HMO) in the
biological activity of
antitumor drugs. It reports data of evaluation of HMO activity in pediatric and adult
cancer patients, which has shown a decrease in HMO activity in one third of patients without clinical signs of hepatopathy and two thirds of those with toxic hepatic damages after prior
chemotherapy. Decreased HMO activity has been found to be stimulated with the
enzyme inductor
zyxorin. Altered biochemical parameters, such as total
bilirubin, ALT and AST, can be corrected with HNO, even if they show a 10-fold deviation from the normal physiological level. The efficacy of
zyxorin was tested in patients with advanced
cancer and concomitant toxic or viral hepatic disorders (grades II-IV by the WHO classification). Stimulation of inhibited HMO activity allows both decrease and prevention of the manifestations of hepatic toxicity due to anticancer
chemotherapy providing a beneficial effect, the dose of
cytostatics being not reduced. The authors concluded that the findings provide strong evidence for their assumption that the efficiency of antitumor
chemotherapy can be enhanced in patients with concurrent hepatic abnormality by stimulating
monooxygenases whose activity is diminished in the majority of these patients.