Low Level LC-MS/MS Quantitation of Psychotherapeutics in Extracellular Fluid for Rat Microdialysis Studies

摘要

The LLOQ of 0.0125 ng/mL obtained for PHA-543613 in aECF enabled a later ECF T_(last) for AUC estimation resulting in higher confidence in the AUC-derived ratios defining the temporal intercompartmental exposure relationships of PHA-543613 in ECF, CSF and plasma. Determination of the bioanalytical LLOQ in conjunction with the desired dose(s) prior to undertaking the microdialysis studies was critical to ensure the availability of a sensitive LC-MS/MS method to detect the predicted ECF concentrations. An exquisitely low LLOQ is often needed for such microdialysis studies due to both the 6.3X dilution factor inherent in the ECF samples and the typically low doses of many psychotherapeutics. In the in vivo dataset presented, ECF concentrations allowed a high-confidence RO projection in SD rats that may be coupled to in vivo pharmacological experiments to better define the PHA-543613 rodent RO-behavioral response relationship. Furthermore, these microdialysis data defined the temporal concentration relationship of ECF, CSF and C_(p,u) in SD rats, which may provide insight to cross-species CNS relationships. Future work will investigate the ability to detect the ECF concentrations of other psychotherapeutics in SD rats to determine the feasibility of pursuing rat microdialysis experiments to enhance our understanding of both preclinical central penetration and translational pharmacology.