High-performance liquid chromatographic method for determining thiopental concentrations in twelve rat tissues: application to physiologic modeling of disposition of barbiturate.

A sensitive, selective and reproducible high-performance liquid chromatographic assay of thiopental concentrations in twelve rat tissues was developed using thiamylal as the internal standard. Samples were homogenized in phosphate buffer, extracted into pentane and chromatographed on a microparticulate octadecyl reversed-phase column using ultraviolet detection at 290 nm. A simple digestive step with collagenase prior to homogenization facilitated analysis of thiobarbiturate in skin. Thiopental extraction recovery from fat exceeded 90%. Assay sensitivity was greater than 1 microgram/ml for tissue and plasma samples as small as 50 microliters. This assay has been applied to physiologic pharmacokinetic studies. The paper also presents typical concentration-time profiles of thiopental in four tissues taken from 74 rats given 20 mg/kg thiopental.