Chem. Pharm. Bull. 55(9) 1379—1382 (2007)

D-glucoside, Fig. 1) is a potent clinical anticancer agent. It is active against several tumors including small lung cancers, lymphoma, leukemia and Karposi’s sarcoma associated with AIDS. It is used as part of the preparatory regimen for bone marrow transplants in patients with advanced hematological malignancies. The mechanism of action of etoposide is unknown but it is a cell-cycle, phasespecific drug that appears to act either by causing DNA breaks by an interaction with DNA-topoisomerase II or by forming free radicals. Methods used previously for the determination of etoposide in human plasma include, high-performance liquid chromatography (HPLC) with UV detection, fluorescence detection and electrochemical detection. HPLC methods based on electrochemical detection also have been used for the analysis of etoposide catechol in human plasma. Those assays using ultraviolet detection have sensitivities down to approximately 100 pg/l. Fluorescence detection improves the specificity and sensitivity such that concentrations as low as 50 pg/l can be measured. Electrochemical detection improves sensitivity further, allowing drug concentrations of 2 to 10 pg/l to be assayed. Radioimmunoassay (RIA) also has been used to measure etoposide. but it is less specific than HPLC and less sensitive than HPLC using electrochemical detection. A method combining liquid chromatography and mass spectrometry is both highly specific and sensitive that simultaneously quantifies etoposide and its catechol metabolite as protein-free and total concentrations in human plasma samples, but requires specialized facilities and is expensive The electroanalytical techniques are well known as excellent procedures for the determination of drug dosage forms and drugs in biological fluids, with the advantages that there is in most instances, no need for derivatization, and that these methods are less sensitive to matrix effects than other analytical techniques. In recent years, the increasing use of carbon paste electrodes (CPEs) for electroanalytical measurement of a variety of organic species of biological and pharmaceutical importance has been reported. The major advantages of carbon paste electrode are low background current; the ease of renewal of the whole electrode providing a fresh surface unaffected by electrode history and this electrode has a wide range of cathodic and anodic applicability.