Analysis of olanzapine in human plasma utilizing reversed-phase high-performance liquid chromatography with electrochemical detection.

A sensitive reversed-phase HPLC method for the analysis of olanzapine in human plasma is described. Isolation of olanzapine from plasma was accomplished by solid-phase extraction utilizing an ion-exchange/reversed-phase cartridge designed for basic drug extraction. The drug was subsequently separated by reversed-phase HPLC and monitored by electrochemical detection (ED). Electrochemical analysis was used to detect olanzapine due to its uniquely low oxidative potential. Ascorbic acid was added to prevent oxidation during extraction. The limit of quantitation for the assay was established at 0.25 ng/ml utilizing a 1-ml human plasma sample. The average inter-day accuracy was 96.6% with a average precision (% C.V.) of 3.22% over the concentration range of 0.25 to 100 ng/ml. This method was applied to human plasma samples from human clinical trials with olanzapine. The HPLC-ED method compared favorably with a negative chemical ionization GC-MS method previously utilized for analysis of olanzapine in human plasma.

Enhancement of blood coagulation by soluble fibrin complexes.

We have detected a species of soluble fibrin complexes with significant biological properties. Agarose gel chromatography of normal plasma or purified fibrinogen previously incubated with small amounts of thrombin revealed the presence of a species of high molecular weight soluble fibrin complexes, which contained only small quantities of fibrinogen by immunological assays but which exhibited enhanced sensitivity to thrombin. In addition, these complexes substantially shortened the thrombin-clotting time of normal plasma and enhanced the resistance of normal plasma to heparin action. Similar thrombin-sensitive soluble fibrin complexes were demonstrated in vivo in rabbits for up to 10 min after the infusion of 50 U of thrombin. Thrombin-sensitive soluble fibrin complexes were also demonstrated in 3 of 12 patients with documented thromboembolic disease and in 2 of 20 patients after major surgery. High molecular weight soluble fibrin complexes, which exhibit enhanced thrombin sensitivity and which are capable of increasing the rate of normal fibrinogen-to-fibrin conversion by thrombin, may appear consequent to clinical thrombosis and situations involving trauma (e.g., major surgery). Such soluble complexes, although they have no proven role in the primary pathogenesis of intravascular thrombosis, may contribute to a temporary "hypercoagulable state" and may accelerate the build-up and extension of already existing thrombotic deposits.