1-Palmitoyl-2-arachidonoyl-sn-glycero-3-phosphoethol (PAPEth) is a form of phosphaytidylethanol (PEth), which is formed primarily by transphosphatidylation of phosphatyidylcholine (PC) by phospholipase D. Most PEth (about 75%) is incorporated into erythrocyte membranes, and is one of the longest-lived circulating EtOH metabolite yet identified. d5-PAPEth has fully deuterated ethanol headgroup and is an analog of one of five most abundant naturally occurring PEth species.