Plasma assay for the antineoplastic agent VP 16-213 (etoposide) using high-performance liquid chromatography with electrochemical detection.

A sensitive high-performance liquid chromatographic (HPLC) assay of the antineoplastic agent VP 16-213 (etoposide) in plasma is described. The system discriminates between the parent compound and possible metabolites, including the aglycone and the cis isomer. After extraction with 1,2-dichloroethane the drugs are chromatographed on a reversed-phase phenyl column with amperometric detection. Quantitative response is linear up to 250 ng/ml for 1 ml human plasma and up to 40.0 mug/ml for 0.1 ml human plasma. The detection limit is ca 2 ng/ml in plasma. Preliminary pharmacokinetic results show that the sensitivity and selectivity of the assay are adequate to establish plasma concentrations over 8-12 half-lives during elimination of the drug.