Pentobarbital quantitation using immunoassays in Reye's syndrome patient serum

Analysis of serum pentobarbital concentrations in 28 specimens from Reye's syndrome patients was conducted with modifications of three nonspecific immunoassay procedures originally designed to detect barbiturates in serum or urine. An adaptation of the urine enzyme-multiplied immunoassay technique (EMIT) Dupont aca barbiturate screen to the quantitation of serum pentobarbital is described. Replicate analysis of control specimens containing pentobarbital across a wide spectrum of concentrations revealed a between-day precision of less than 6%. Regression analysis revealed excellent agreement with a high-performance liquid chromatography (HPLC) method: (HPLC) = 0.98 (aca) - 0.07 (r = 0.97). Multiple linear regression analysis with a serum EMIT barbiturate screen and a urine fluorescence polarization immunoassay screen modified to quantitate pentobarbital in serum revealed excellent agreement among all methods, demonstrating that immunoassays offer a reliable approach to pentobarbital quantitation.