Antineoplastic Drugs

The limited scope of therapeutic drug-level monitoring in cancer chemotherapy results from the often complex biochemical mechanisms that contribute to antineoplastic activity and obscure the relationships among drug serum levels and therapeutic benefits. Moreover, new agents for cancer chemotherapy are being introduced at a more rapid rate than for the treatment of other diseases, although the successful application of therapeutic drug-level monitoring may require several years of intensive study of the significance of serum drug levels. However, drug level monitoring can be of considerable value during phase I clinical trials of new antineoplastic agents in order to assess drug metabolism, bioavailability, and intersubject variability; these are important parameters in the interpretation of clinical studies, but have no immediate benefit to the patient. High performance liquid chromatography (HPLC) probably represents the most versatile and easily adaptable analytical technique for drug metabolite screening (1 ). HPLC may therefore now be the method of choice during phase I clinical trials of antineoplastic drugs. For example, within a single week we developed an HPLC assay—using a C₁₈ reverse-phase column, UV detection, and direct serum injection after protein precipitation—for the new radiosensitizer, misonidazole (2 ).