Acute myocardial uptake of digoxin in humans: correlation with hemodynamic and electrocardiographic effects.

Acute myocardial uptake of digoxin was measured at a constant paced heart rate (75 beats/min) for 30 min after an intravenous bolus injection of 500 micrograms of digoxin in 14 patients with ischemic heart disease. Myocardial digoxin content, determined by serial measurement of aortocoronary sinus digoxin concentration gradients and coronary sinus blood flow, was expressed relative to coronary sinus blood flow at rest and correlated with simultaneous hemodynamic and electrocardiographic changes. Myocardial digoxin uptake was extensive (4.1 +/- 0.7% of total injected dose at 30 min) and prolonged, with rapid initial uptake (75.3 +/- 6.6% of maximum at 3 min), followed by a variable phase of slower accumulation. Peak left ventricular positive first derivative of left ventricular pressure (dP/dt) increased progressively (p less than 0.01), with a similar time course to that of myocardial digoxin accumulation; maximal change was 18.5 +/- 4.7% at 27 min. The ratio of inotropic effect to myocardial digoxin content did not vary significantly over the period of the experiment. However, peak inotropic effects in individual patients were not significantly related to peak myocardial digoxin content. The spontaneous PR interval increased transiently, with a peak increase of 5.9 +/- 1.8% (p less than 0.05) 12 min after digoxin administration. It is concluded that after intravenous bolus administration, 1) peak effects of digoxin on atrioventricular (AV) conduction occur early, whereas positive inotropic effects increase progressively for greater than or equal to 27 min; and 2) digoxin accumulation in the human myocardium is prolonged and is a determinant of inotropic effects, but not of prolongation of AV node conduction.

Simultaneous HPLC gradient analysis of 15 benzodiazepines and selected metabolites in postmortem blood.

The simultaneous identification and quantitation of 15 benzodiazepines and selected metabolites in postmortem blood, serum, or liver homogenate is described. The assay involves extraction with diethylether, followed by an acid clean-up step of the ether. Chromatographic separation was achieved on a Nova-Pak phenyl 18 column using ultraviolet detection at 240 nm. A gradient HPLC system was developed to improve separation of nitro-reduction metabolites from the solvent front and endogenous peaks. The mobile phases consisted of a gradient from 15 to 28% acetonitrile in 40 mM potassium phosphate buffer. Within-run and day-to-day precision were generally 10-15%. The method described is sensitive and reproducible for the analysis of benzodiazepine concentrations in postmortem tissues.

Capillary gas chromatographic drug screen for use in forensic toxicology.

A screening method is presented involving the use of capillary gas chromatography using a BP-5 column and nitrogen-phosphorous detection. This method is a quick yet reliable procedure for a large range of neutral and basic drugs and uses 1 mL or less of blood. Running standards that contain a number of commonly observed drugs with each batch of cases allows for more accurate tentative identifications of likely drugs in unknown cases and also provides a measure of quality assurance. This method is suitable for postmortem and clinical blood samples as well as plasma and serum.