Microassay of drugs and modern measurement techniques

Summary Details of the development of conventional analytical methods for the determination of drugs in pediatric plasma/serum samples via microassays are presented. Examples of the development of small‐volume sampling and the use of the newer detection systems such as LC/MS/MS for enhanced detection are presented. Dried blood spot sampling has conventionally been used for the study of inborn errors of metabolism using Guthrie cards. Limited applications in the area of drug‐level determination, for example, in therapeutic drug monitoring had been reported but the methodology had not been widely used up until relatively recently. In the last few years, there has been a resurgence of interest in this methodology for drug‐level determinations, and examples of drug analysis in pediatric and neonatal patients where the small‐volume samples are particularly useful are presented. The application of the methodology in pharmacokinetic/pharmacodynamic studies is discussed. The utilization of solid‐phase microextraction and stir bar sorptive extraction in drug analysis is presented. Clinical applications of these methodologies are reported including the development of in vivo solid‐phase microextraction.