POSTMORTEM CHANGES IN BLOOD TRANYLCYPROMINE CONCENTRATION - COMPETINGREDISTRIBUTION AND DEGRADATION EFFECTS

Site and temporal changes in tranylcypromine (TCP) and lithium concent rations in blood were studied in a human poisoning case. Blood samples from peripheral vessels and six central vessels were obtained at 0, 6 , 24, 48 and 72 h after starting the autopsy. Nine tissue samples were obtained on completion. TCP showed preferential concentration in live r (2.21 mug/g) and brainstem (2.46 mug/g). There was a moderate post m ortem redistribution phenomenon with TCP concentrations lowest in peri pheral blood (0. 17 mug/m1) at 0 h and highest in central vessels at 2 4 h (0.52 mug/ml). At 72 h blood TCP concentrations fell below those a t 0 time but the samples showed marked putrefactive changes. Control b lood samples spiked with TCP and incubated for 48 h at 37-degrees-C sh owed a 58% fall in drug concentration. By contrast with TCP, lithium, which has a small Vd (0.8 1/kg) and is chemically stable, did not show this pattern of change in blood concentration. The site and temporal differences in TCP concentration in blood can be explained by the comp eting effects of post mortem redistribution and drug degradation. Redi stribution is an early post mortem phenomenon characterised by diffusi on, along a concentration gradient, from drug reservoirs in solid orga ns into adjacent blood vessels. Drug degradation is a later phenomenon associated with putrefactive change.