Quantitation of diltiazem in human cardiac tissue using high-performance liquid chromatography

A new high-performance liquid chromatographic method has been developed for the determination of diltiazem in human cardiac tissue. Tissue samples are homogenized and digested with trypsin solution. Diltiazem and the internal standard are extracted with acetone. The extract is evaporated to dryness and reconstituted in potassium phosphate buffer. Samples are then cleaned up with solid-phase extraction columns. Diltiazem and the internal standard show recoveries of 59% +/- 16 and 52% +/- 13. The linearity range is 0.12-2.25 ng/mg wet weight. The limit of quantitation is 0.12 ng/mg (w/w). The percentage coefficient of variation of intra-assay varies between 3.57 and 11.2, and that of interassay varies between 5.42 and 11.7. As an application of the assay, a diltiazem cardiac tissue level in a patient on oral therapy for supraventricular tachycardia is reported.