High-performance liquid chromatographic determination of the plasma concentration of K-27, a novel oxime-type cholinesterase reactivator

A simple and reliable HPLC method for the determination of the plasma level of K-27, an oxime type antidote of use in organophosphorus poisoning is presented. Separation was carried out by HPLC using an octyl silica stationary phase and a mobile phase consisting of 93% phosphate buffer (pH 2.6) containing octane sulfate sodium salt, and 7% methanol. Quantitative absorbance was monitored at 286 nm. The calibration curve was linear through the range of 1.25-200 μg/mL, that is well beyond the detected plasma level range of K-27. Limit of quantitation was 5 μg/mL. Intra-day and inter-day precisions of the HPLC determinations gave standard deviations as 0.77 and 2.67%, respectively. Following intramuscular administration of 50 μmol (22.31 mg) K-27 in rats, the maximum of K-27 concentration in plasma was reached at about 15 min giving 186 μg/mL and the t_1/2 was 85 min. K-27 displays initial (from 15 trough 120 min) zero order elimination kinetics. Similar results have been found after intraperitoneal administration.