Determination of sematilide in plasma by high-performance liquid chromatography

A method for the determination of sematilide levels in human plasma is described. After the addition of an internal standard, plasma samples are adjusted to pH 8.5 and extracted with a solution of 7.5% isopropanol in methylene chloride. Separation from co-extracted matrix constituents is performed by reversed-phase HPLC followed by UV detection at 254 nm. The assay is linear in the concentration range 12-2400 ng/mL when 0.5-mL aliquots of plasma are extracted. Application of the method to the analysis of samples obtained from eight healthy volunteers given an oral dose of 100 mg of sematilide hydrochloride is shown.