Simultaneous determination of pentoxifylline and three metabolites in biological fluids by liquid chromatography.

We describe a sensitive and specific liquid-chromatographic assay for pentoxifylline and three of its metabolites in human plasma and urine. Addition of hydrochloric acid to the sample before extraction, and incorporation of acetic acid in the chromatographic eluent, allow the simultaneous determination of the four compounds plus an internal standard in one chromatographic run. Unlike gas-chromatographic procedures, this method does not involve derivatization no similar analysis of serum or plasma samples has been described before now. The method has been applied successfully to routine analysis and to pharmacokinetic studies.