Fast, simple and cost-effective determination of thiopental in human plasma by a new HPLC technique

Background: Thiopental is an anaesthetic drug that is largely used in both short-term and long-term infusion. After long-term infusion of thiopental, non-linear and inter-individual-dependent pharmacokinetics occur because of the saturation and/or induction of the metabolism. Clinical monitoring is important so that therapeutic adjustments can be made in many of the differ ent pharmacological treatments, especially when long-term infusion is requi red. We describe a new, rapid HPLC method for the determination of plasma t hiopental. Methods: Sample preparation involved precipitation of plasma pro teins using a mixture of methanoI, zinc sulfate and ethylene glycol, and co ntaining the internal standard 5-ethyl-5-p-tolylbarbituric acid. After addi ng trichloroacetic acid, the sample was centrifuged and the supernatant was injected into a C,, reversed-phase column. The mobile phase used was water -methanol-acetonitriIe (50:40:10, v/v). The eluent was monitored at 290 nm. Results: The calibration curve was linear from 0.2 to 100 mug/mL. Precisio n, calculated as the coefficient of variation (%): was in the range of 3.62 -0.70% for the within-day assay and 5.77-1.51% for the between-day assay. T he absolute recoveries obtained from supplemented samples were never less t han 100%. Conclusions: This technique shows good reliability and seems to b e suitable for a very fast and simple therapeutic monitoring of plasma thio pental. (C) 2001 Elsevier Science B.V. All rights reserved.