Objective. - To determine the clinical utility of fatty acid ethyl esters (FAEEs) in the blood as a short-term confirmatory marker for ethanol intake and a longer-term marker for ethanol intake after ethanol is no longer detectable. Design. - Single-center controlled clinical trial and a blinded comparison involving 48 blood samples that were positive, negative, or equivocal for blood ethanol. Participants. - Seven healthy subjects (4 men and 3 women, aged 21 to 23 years) participated in the clinical trial. Blood samples from participants for the blinded comparison portion of the study were numbered from 1 to 48 and not identified by name. Intervention. - The 7 healthy subjects ingested a known amount of ethanol at a fixed rate. The concentration of FAEEs in the blood after ethanol intake was determined for a period of up to 24 hours. There was no intervention in the blinded comparison study. Main Outcome Measures. - In the clinical trial, a pharmacokinetic analysis of FAEE concentration in the blood after ethanol intake was completed for 7 individuals whose blood ethanol level was elevated from 25 to 35 mmol/L. In the blinded comparison, the 48 blood samples that were positive, negative, or equivocal for blood ethanol were analyzed for FAEE concentration. Results. - In the clinical trial, the disappearance of FAEEs from the blood followed a decay curve that initially resembled the decay curve for blood ethanol. However, because of a very slow secondary elimination phase, the FAEEs were found to persist in the blood for at least 24 hours after ethanol intake was completed. In the blinded comparison, all 20 samples that were positive for ethanol were positive for FAEEs, 7 of 7 samples equivocal for ethanol were positive for FAEEs, and 21 of 21 negative samples for ethanol were negative for FAEEs. Conclusions. - Serum concentration of FAEEs can serve as an excellent short-term confirmatory test for ethanol intake as well as a longer-term marker of ethanol ingestion. Measurement of FAEEs in the blood may be a more sensitive indicator of ethanol ingestion than the measurement of blood ethanol.
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