Gas chromatographic determination of pentoxifylline and its major metabolites in human breast milk.

A method has been developed for determination of the xanthine drug, pentoxifylline, and three of its metabolites (a secondary alcohol and two carboxylic acids) in human milk. The method requires pre-extraction with hexane to remove lipids followed by extraction with dichloromethane or dichloromethane-isopropanol (4:1). Absolute extraction recoveries were between 76-90%. Pentoxifylline and its alcohol metabolite (as the trifluoroacetate) and the carboxylic acid metabolites (as ethyl esters) were measured in separate gas chromatographic steps using a nitrogen detector. Determinations of pentoxifylline and its three metabolites were 96-99% accurate and standard deviations of 5-10% were observed for samples at or above the lower practical sensitivity limit (10 ng/ml) for the assay. Pentoxifylline and its metabolites were stable in breast milk for three weeks when stored at -15 degrees C.