Development and evaluation of selected assays for drugs and drug metabolites in biological materials

Abstract

An over-all strategy for developing and evaluating assays for drugs in biological materials is described. Each stage, i.e., starting points, nature of the biological sample, characterisation of the compound, choice of the analytical method, selection of an internal standard, isolation procedure, calibration, evaluation and quality control, are discussed separately. Chromatographic techniques, which are usually preferable to approaches not involving a separation step, such as competitive binding assays, are emphasised. Some controversial points concerning the use of internal standards are discussed and special approaches for calibration, including an outline of assay criteria to be evaluated, are presented. The general principles are illustrated with examples from the authors' own experience.