Duragesic® transdermal patch:: Postmortem tissue distribution of fentanyl in 25 cases

Fentanyl is a potent, short-acting narcotic analgesic widely used as a surgical anesthetic and for the control of pain when administered in the form of a transdermal patch. The success of the patch can be attributed to fentanyl's low molecular weight and its highly lipophilic nature, which enables it to be readily absorbed through the skin and subsequently distributed throughout the body. Over the past three years, the Los Angeles County Coroner's Toxicology Laboratory has encountered 25 cases involving Duragesic patches (fentanyl), and their postmortem tissue distributions are presented here. The analysis of fentanyl from postmortem specimens (3-mL or g sample size) consisted of an n-butyl chloride basic extraction followed by identification and quantitation on a gas chromatograph-mass spectrometer using the selected ion monitoring (SIM) mode. The fentanyl ions monitored were m/z 245, 146, and 189 and the internal standard, fentanyl-d5 ions, were m/z 250, 151, and 194 (quantitation ion underlined). The linear range of the assay was 1.67 μg/L to 500 μg/L with the limit of quantitation and detection of 1.67 μg/L. The postmortem tissue distribution ranges of fentanyl in the 25 fatalities were as follows: heart blood, 1.8-139 μg/L. (23 cases); femoral blood, 3.1-43 μg/L (13 cases); vitreous, +<2.0-20 μg/L (4 cases); liver, 5.8-613 μg/kg (22 cases); bile, 3.5-262 μ/L (15 cases); urine, 2.9-895 μg/L (19 cases); gastric, 0-1200 μg total (17 cases); spleen, 7.8-79 μg/kg (3 cases); kidney, 11 μg/kg (1 case); and lung, 31 μg/kg (1 case). The age of the decedents in this study ranged from 19 to 84, with an average age of 46. The modes of death included 15 accidental, 5 natural, 3 suicidal, and 2 undetermined. The main objectives of this paper are to show the prevalence of fentanyl patches in our community and to aid the forensic toxicologist with the interpretation of postmortem fentanyl levels in casework.