Background The purpose of this study was to characterize the pharmacokinetics of two homologues of phosphatidylethanol (PEth) and their combined total in uncoagulated, whole blood samples taken from participants in a human clinical lab study after consumption of low doses of ethanol. Methods As part of a larger study, 14 male and 13 female participants received either 0.25 or 0.50 g/kg oral doses of ethanol during a 15 min period. Blood samples were collected before and throughout 6 h after each ethanol dose on the day of consumption, and then every 3 days during the next 14 days. PEth 16:0/18:1 and PEth 16:0/18:2 levels were quantified in blood samples by HPLC/MS/MS and reported separately or as their combined total (combined PEth). Breath alcohol concentrations (BrAC) were measured concurrently with each blood collection. Transdermal alcohol concentrations (TAC) were measured every 30 min during the entire 22 day study to confirm the absence of drinking during a 7 day period before and the 14 day period after ethanol consumption. Results (1) Single doses of 0.25 and 0.50 g ethanol/kg produced proportional increases in BrAC and combined PEth levels of all participants; (2) the areas under the curve (AUC) for each participant’s BrAC levels during the 6 h period after ethanol administration were correlated with AUCs of cPEth (calculated as the AUC of the increase above baseline for combined PEth); (3) the mean half-life of combined PEth, determined during the 14 day period after ethanol consumption, was 4.6 ± 3.5 (SD) days (range: 1.0 to 13.1 days). Conclusions Combined PEth is a sensitive biomarker for the identification of relatively low levels of ethanol consumption. The measurement of these two homologues may provide additional sensitivity to identify low levels of drinking.

The results of this study support the use of PEth 16:0/18:1 and 16:0/18:2 as biomarkers for alcohol consumption. Because of consistent pharmacokinetic differences, the levels of these 2 PEth homologues may provide more information regarding the quantity and recentness of alcohol consumption than either alone.

Reliance upon the AMS criteria for alcohol detection affords a high specificity for detection of heavy drinking but is a poor indicator of abstinence rates. In contrast use of our Research Rules provides more sensitive means to quantify either any drinking or low-moderate levels of drinking while still maintaining good specificity.

Aims: Monitors of transdermal alcohol concentration (TAC) provide an objective measurement of alcohol consumption that is less invasive than measurements in blood, breath or urine; however, there is a substantial time delay in the onset of TAC compared to blood or breath alcohol concentrations (BrACs). The current study examined the characteristics of the delay between peak TAC and peak BrAC. Methods: Data was aggregated from three experimental laboratory studies (N = 61; 32 men, 29 women) in which participants wore a TAC monitor and BrAC was monitored while drinking one, two, three, four and five beers in the laboratory. Analyses examined the sex-and dose-related differences in peak BrAC and TAC, the time-to-peak BrAC and TAC, and time lag between the peak BrAC and TAC values. Results: The times-to-peak were an increasing function of the number of beers consumed. At each level of beer consumption the peak TAC averaged lower than peak BrAC and times-to-peak TAC were longer than for BrAC. The time-to-peak BrAC and TAC was longer for women than men. The congruence between peak TAC and BrAC increased as a function of the beers consumed. No sex difference in the time lag between peak BrAC and TAC was detected. Conclusions: The congruence between TAC and BrAC and time lags between TAC and BrAC are related to the number of beers consumed. Peak values of TAC and BrAC became more congruent with higher doses but the time lag increased as a function of the amount of alcohol consumed. Short summary: The time delay (or lag) and congruence between transdermal vs. BrACs increases as the number of beers increases. Though sex differences are evident in peak transdermal and BrACs, no sex differences were evident in the time lag and the congruence between transdermal and breath alcohol concentrations.

Alcohol consumption is typically assessed via self-report methods, though there are concerns over the accuracy of this information. Transdermal alcohol monitoring can passively and continuously measure alcohol consumption with minimal interference in daily life. The current study examines the correspondence between daily self-reported alcohol consumption and transdermal alcohol monitors. Thirty-two healthy men (n = 16) and women (n = 16) wore a transdermal alcohol monitor for 28 days. Participants were instructed to drink as they usually do and prompted daily with a survey link to report yesterday's drinking. Data analyses focused on the following comparisons: (1) the overall correspondence between self-reported drinking and TAC readings; (2) the sensitivity of various TAC criteria thresholds to detect self-reported drinking (TAC thresholds of none, low, moderate, and heavy); and (3) the risks of false positive TAC findings using self-reported drinking as the Gold Standard. Participants self-reported drinking a total of 324 days, of which, TAC events were detected on 212 days (65.4%). When participants self-reported not drinking (399 days), zero TAC was also found on 366 days (92%). The correspondence between self-reported drinking and transdermal concentrations tended to be good: overall, when self-reported drinking was reported, TAC also detected drinking 65.4% of the time.