Detection of acute fentanyl exposure in fresh and decomposed skeletal tissues

The detection of acute fentanyl exposure in fresh and decomposed skeletal tissues (marrow and bone), by automated enzyme-linked immunosorbent assay (ELISA) is described. Rats (n=15) were administered fentanyl acutely at a dose of 0 (n=3), 15 (n=3), 30 (n=3) or 60 microg/kg (n=6) by intraperitoneal injection, and euthanized within 20 min. Femora and tibiae were extracted from the fresh corpses and marrow was isolated from the femoral and tibial medullary cavities. The remains were then allowed to decompose outdoors to the point of complete skeletonization, and vertebrae and pelvi were recovered for analysis. In all cases, bones were cleaned in alkaline solution and then ground into a fine powder. Marrow was homogenized in alkaline solution. Fentanyl was extracted from ground bone by methanolic extraction. Extracts were adjusted to pH 6 and analyzed by ELISA. Perimortem heart blood was also collected and diluted in phosphate buffer prior to screening by ELISA. The effect of tissue type on ELISA response was examined through determination of binary classification test sensitivity and the relative decrease in absorbance (%DA, drug-positive tissues vs drug-free controls) in each tissue type. Overall, the %DA varied significantly between extracts from different skeletal tissues under a given dose condition, according to the general order of marrow>vertebrae approximately pelvi>epiphyseal bone approximately diaphyseal bone. Binary classification test sensitivity values for fentanyl in marrow, fresh epiphyseal (femoral and tibial) bone, fresh diaphyseal (femoral and tibial) bone, decomposed vertebrae and decomposed pelvic bone were 100%, 16-33%, 0-16%, 0-33% and 66-100%, respectively, at the 60 microg/kg dose level. While mean %DA values showed a strong positive correlation with those in marrow and blood measurements and the administered dose (r=0.997 and 0.986), such a correlation was not observed in assays of decomposed tissues (r=-0.157 and -0.315). These results suggest that the type of skeletal tissue sampled and position within a given bone may be important considerations in the choice of substrate for fentanyl screening in skeletal tissues, but that quantitative analysis of drugs in decomposed bones may be of limited interpretive value.