Determination of Pimavanserin and Its Metabolites in Mouse Plasma Using LC-MS/MS: Investigating Pharmacokinetics Following Different Routes of Administration

Objective: The aim was to develop a straightforward, efficient, and sensitive LC-MS/MS assay for quantifying pimavanserin (ACP-103) and its active metabolite (N-desmethyl pimavanserin, AC-279) in mouse plasma to assess the pharmacokinetics of ACP-103 following various routes of administration in mice. Methods: Mouse plasma samples were prepared using acetonitrile protein precipitation. Chromatographic separation was achieved on a Phenomenex C18 column with a mobile phase consisting of 0.1% formic acid in water (solvent A) and 0.1% formic acid in acetonitrile (solvent B). A total of 54 male mice were divided into nine groups (six per group) and received different doses (0.3, 1, 3 mg/kg) of Pimavanserin tartrate via nasal drip, intramuscular injection, or subcutaneous injection. Venous blood samples were collected at various time points pre- and post-administration, and plasma concentrations of ACP-103 and AC-279 were determined. Results: The intra-day and inter-day accuracy for ACP-103 and AC-279 in quality control plasma samples ranged from 90.87% to 105.50%, with precision within 20% and 10%, respectively. Comparative exposure of Pimavanserin tartrate was observed following nasal drip and intramuscular administration, while subcutaneous injection resulted in lower exposure. Increasing doses led to higher drug concentrations for all routes, with no significant differences in AC-279 production. Conclusion: The developed LC-MS/MS method was effectively utilized for pharmacokinetic studies in mice after administration of Pimavanserin tartrate at 0.3, 1, and 3 mg/kg via nasal drip, intramuscular injection, and subcutaneous injection. Notable differences in the pharmacokinetic profiles of ACP-103 were observed depending on the route of administration.