Quantitation of diltiazem and desacetyldiltiazem in dog plasma by high-performance liquid chromatography

A high-performance liquid chromatographic procedure was developed for the determination of diltiazem and desacetyldiltiazem in dog plasma. Two milliliters of plasma is extracted with a hexane-2-propanol mixture. The assay uses a reverse-phase column maintained at 55 degrees C with a silica saturation column and a pellicular precolumn. The mobile phase is acetonitrile-water (50:50) at pH 6.6 with 1.5-g/L heptanesulfonic acid added as the ion-pair reagent. The procedure is sensitive to 5 ng/mL for both compounds in dog plasma and is linear up to 2000 ng/mL for diltiazem and 1000 ng/mL for desacetyldiltiazem . Preliminary dog mean plasma profiles of diltiazem and desacetyldiltiazem are presented.