Gas chromatographic determination of loxapine and its five principal metabolites in human plasma.

Abstract

Loxapine (I) [1977-10-2] and its 5 principal metabolites (8-hydroxyloxapine [61443-77-4], 7-hydroxyloxapine [37081-75-7], amoxapine [14028-44-5], 8-hydroxyamoxapine [61443-78-5], and 7-hydroxyamoxapine [37081-76-8]) were detd. by gas chromatog., after extn. from human plasma into EtOAc in the presence of (NH4)2CO3, purifn. by reextn., trifluoroacetylation and silylation. Sepn. was effected on a capillary column having an N-P-specific thermionic detector. Clothiapine was a better internal std. than 8-methoxyloxapine, its coeff. of variation being smaller. The limit of sensitivity for 7-hydroxyamoxapine, the compd. most difficult to detect, was 5 ng/mL of plasma. The coeff. of variation for intrasystem reproducibility was <6%. [on SciFinder (R)]