Stability of diltiazem in whole blood: forensic implications

The stability of diltiazem (DTZ) in whole blood and in postmortem samples was investigated. In the first study, an aliquot of outdated Red Cross blood with sodium fluoride added as a preservative was spiked with DTZ and stored for one year under three separate conditions: room temperature, 4 degrees C, and -20 degrees C. DTZ and one of its major metabolites, desacetyldiltiazem (DAD), were quantitated at given intervals during this period. In the second study, case postmortem blood samples (n = 36) that exhibited different degrees of putrefaction were spiked in a similar fashion and the stability of DTZ was determined after storage at 4 degrees C for 92 days. DTZ and DAD were extracted as bases, using mild pH conditions to prevent the hydrolysis of DTZ, and quantitated by an HPLC system equipped with a diode array detector and a Supelcosil LCDP column, 5 microns, 250 mm x 4.6 mm inside diameter. Approximately 50% of DTZ was lost in the Red Cross blood stored at room temperature and 4 degrees C, after 19 and 124 days, respectively. This was associated with concomitant appearance and comparable increase in DAD concentration, presumably due to the in vitro hydrolysis of DTZ to DAD. No significant loss of DTZ was observed in the -20 degrees C samples. Similar changes in DTZ and DAD concentrations were seen in postmortem blood samples stored at 4 degrees C for 92 days, though notably, the extent of loss of DTZ varied from complete to negligible. The data suggest that the potential for in vitro conversion of DTZ to DAD should be considered for proper interpretation of postmortem DTZ/DAD findings. Several cases examined in this laboratory will be used to discuss other forensic implications.