A rapid method for detecting barbiturates in serum using EI-SIM

A simple and rapid method for analysis of barbiturates in serum has been developed. In order to extract and clean barbiturates in serum, a separation column packed with Extrelut and Florisil was used, and the eluate was directly analyzed by means of electron impact selected ion monitoring (EI-SIM). Selected ions used were base peak ions of 10 barbituartes, and the internal standard used was allobarbital or secobarbital. The calibration curves were linear over the range 0.5-5 ng. Extraction of replicate serum samples containing 20 micrograms/1.5 ml and 5 micrograms/1.5 ml resulted in a recovery of 87.2-105.2% and 81.6-104.6%, respectively, with the exception of phenobarbital, which was 151.9% and 172.1%, respectively. Secobarbital was also analyzed in the serum of 13 patients who had been given secobarbital intravenously. In 3 out of 10 cases, secobarbital levels greater than 1 micrograms/ml were detected more than 72 h after administration. This method seems to have possibilities for clinical use.

An interactive program for pharmacokinetic modeling

A computer program, PharmK, was developed for pharmacokinetic modeling of experimental data. The program was written in C computer language based on the high-level user-interface Macintosh operating system. The intention was to provide a user-friendly tool for users of Macintosh computers. An interactive algorithm based on the exponential stripping method is used for the initial parameter estimation. Nonlinear pharmacokinetic model fitting is based on the maximum likelihood estimation method and is performed by the Levenberg-Marquardt method based on chi 2 criterion. Several methods are available to aid the evaluation of the fitting results. Pharmacokinetic data sets have been examined with the PharmK program, and the results are comparable with those obtained with other programs that are currently available for IBM PC-compatible and other types of computers.

Post-mortem drug redistribution--a toxicological nightmare

Detailed human case data is presented to illustrate the dramatic extent of the phenomenon of post-mortem drug redistribution. The data suggests that there is a post-mortem diffusion of drugs along a concentration gradient, from sites of high concentration in solid organs, into the blood with resultant artefactual elevation of drug levels in blood. Highest drug levels were found in central vessels such as pulmonary artery and vein, and lowest levels were found in peripheral vessels such as subclavian and femoral veins. In individual cases, in multiple blood samples obtained from ligated vessels, concentrations of doxepin and desmethyldoxepin ranged from 3.6 to 12.5 mg/l and 1.2 to 7.5 mg/l, respectively; amobartital, secobarbital and pentobarbital from 4.3 to 25.8 mg/l, 3.9 to 25.3 mg/l and 5.1 to 31.5 mg/l respectively; clomipramine and desmethylclomipramine from 4.0 to 21.5 mg/l and 1.7 to 8.1 mg/l, respectively and flurazepam 0.15 to 0.99 mg/l; imipramine and desipramine from 4.1 to 18.1 mg/l and 1.0 to 3.6 mg/l, respectively. We conclude that this poorly studied phenomenon creates major difficulties in interpretation and undermines the reference value of data bases where the site of origin of post-mortem blood samples is unknown.

Post mortem kinetics of secobarbital

Post-mortem changes in barbiturate concentrations were evidenced using a rat-secobarbital model. The method used for the extraction and HPLC assay of barbiturates is suitable for all biologic fluids and post-mortem tissues. Kinetic data obtained is of excellent quality. Various modelization constants were defined. This experimental work emphasizes the difficulty of post-mortem toxicology, as concentrations found at the time of autopsy may be different from concentrations at the time of death, in blood as well as in tissues.