Chiral assay methods for lifibrol and metabolites in plasma and the observation of unidirectional chiral inversion following administration of the enantiomers to dogs.
Lifibrol, a new drug for the treatment of hypercholesterolemia, contains a stereogenic center bearing a secondary alcohol group. A normal-phase achiral-chiral HPLC separation of the enantiomers of lifibrol and two of its metabolites was developed and validated for quantitation in dog plasma. A silica and a Chiralcel OD-H column were operated in series and all six enantiomeric components and internal standard were directly separated. An initial solid-phase extraction (phenyl) clean-up step and a column-switching step to eliminate late-eluting compounds were also utilized. The solid-phase extraction step was automated using a robotic system. Assay development, validation, and application of the method to a bioavailability study of the racemate and enantiomers of lifibrol in dogs are described. The lower limit of quantitation was 0.0125 microgram/ml for each enantiomer of lifibrol using 200 microliters of dog plasma with UV detection (255 nm). In dog plasma following oral or intravenous administration of the racemate, the (R)/(S) ratio of the enantiomers of lifibrol was greater than one and increased with time. Following administration of the individual enantiomers, chiral inversion of the (S)-enantiomer but not the (R)-enantiomer was observed.
Walters
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Department of Drug Metabolism Research, Upjohn Company, Kalamazoo, MI 49001.
Hsu
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D000284:Administration, Oral; D000818:Animals; D001322:Autoanalysis; D001682:Biological Availability; D000440:Butanols / Q000097:blood* / Q000493:pharmacokinetics; D002851:Chromatography, High Pressure Liquid; D004285:Dogs; D005260:Female; D062385:Hydroxybenzoates / Q000097:blood* / Q000493:pharmacokinetics; D000960:Hypolipidemic Agents / Q000097:blood* / Q000493:pharmacokinetics; D007275:Injections, Intravenous; D008297:Male; D012371:Robotics; D013056:Spectrophotometry, Ultraviolet; D013237:Stereoisomerism
D000440:Butanols; D062385:Hydroxybenzoates; D000960:Hypolipidemic Agents; C059343:lifibrol