Validation of HPLC-MS/MS methods for analysis of loxapine, amoxapine, 7-OH-loxapine, 8-OH-loxapine and loxapine N-oxide in human plasma.

Background: Two ESI-LC-MS/MS methods were validated for the quantitative analysis of loxapine, amoxapine, 7-OH-loxapine, 8-OH-loxapine and loxapine N-oxide in human K(2)EDTA plasma. Cation-exchange solid-phase extraction (SPE) was used to extract loxapine, amoxapine and the two hydroxylated metabolites, and organic precipitation was used to quantify loxapine N-oxide.

Results: Both methods were shown to be accurate (±13%), intra-assay precision was less than 15%, and inter-assay precision was less than 10% in all instances across the entire dynamic range of the assays (0.