Optimization of Capillary GC Conditions for the Analysis of Psychotropic Drugs at Subnanogram Concentrations in Plasma

Following a single therapeutic dose many psychotropic drugs are present in plasma at sub-ng concentrations. As a consequence many of the pharmacokinetic parameters of these drugs have been derived from steady-state data using relatively insensitive analytical methodology. In order to gain pharmacokinetic data from a single dose it is necessary to develop a routine assay with high sensitivity and specificity. This requires optimization of Chromatographic and extraction conditions, as now briefly illustrated for two psychotropic agents — thiothixene (TTX), and flurazepam together with its major metabolites desalkylflurazepam (DAF) and hydroxyethylflurazepam (HEF).