Sensitive and Rapid Blood and Tissue HPLC Oxime Assay and Pharmacokinetics of MMB-4 in Guinea Pigs and African Green Monkeys

摘要

We developed a rapid and sensitive assay for pyridinium oximes in plasma and tissues. Samples are prepared by acidification and then deproteinized by ultrafiltration. The oximes are measured during sample HPLC fractionation over a cation-exchange column with UV detection. The assay is suitable for analysis of mono- and di-pyridinium oximes, but was originally developed for the measurement of the oxime MMB-4. For both plasma and tissue sources, the LLOD was 0.0005 microgram and the LOQ was 0.001 to 2.5 microgram. The assay requires as little as 50 microliters of whole blood or 30 microliters of tissue homogenate. The assay was used for plasma pharmacokinetic studies from a single intramuscular injection of MMB-4 (dichloride or dimethylsulfonate salt) in nonhuman primate African green monkeys (AGM), and the plasma and tissues of the rodent guinea pig (GP). For the two species, both MMB-4 salts were pharmacokinetically equivalent. In AGM plasma, the Cmax and the area under the curve (AUC) varied dose-dependently with a Tmax of approximately 20 min and mean residence time (MRT) was approximately 92 minutes for all doses of both salts. In GP plasma and muscle tissues, the Cmax and AUC also varied dose- dependently. The plasma Tmax was about 34 to 42 min while the muscle tissue levels peaked at 5-20 min. The tissue concentrations were much lower than the plasma. The tissue levels peaked at 5-20 min depending on the tissue with a concentration ranking of diaphragm > heart > thigh muscle.