Intra-individual and inter-individual variation in breath alcohol pharmacokinetics: The effect of food on absorption

Eight male and 8 female subjects underwent serial breath alcohol concentration (BrAC) measurements in the fasting state, following a snack of crisps and following a light meal. BrAC versus time curves were constructed for each subject and the values of peak BrAC (C-max), theoretical (extrapolated) BrAC at zero time (C-0), time taken to reach peak (T-max) and rate of elimination (beta) were recorded directly from the curves. In all subjects values of C-0 extrapolated from the post-meal BrAC-time curves were significantly lower than in the fasting and snack fed states. Since Widmark factor (W.F.) is inversely proportional to C-0, values of WF calculated from extrapolated C-0 after a meal were spuriously high. WF obtained from the fasting BrAC-time curves were usually only slightly higher than those calculated by the Forrest mathematical method. C-max was highest in fasting subjects (mean 30.5, range 22.5-42 mu g/100 ml) and lowest after a meal (mean 21.4, range 13.5-32 mu g/100 ml). T-max was shortest after a meal and also remarkably consistent (mean 22, range 17-50 min). 'Overshoot' was seen in most fasting subjects within about 40 min of consuming alcohol. Elimination of alcohol from breath was slightly lower after a meal (mean 5.4, range 3.9-8.5 mu g/100 ml/h) than after either fasting (mean 6, range 4.7-7.3 mu g/100 ml/h) or a snack (mean 6, range 4.4-8.8 mu g/100 ml/h). The availability of alcohol for absorption (as a percentage of the predicted value) was almost complete after fasting or a snack but after a meal was reduced to only 66% in females and 71% in males. The practical significance of this much reduced peak BrAC after food occurs in relation to forward or back calculations and cases involving post-accident drinking ("the hip flask" defence) as ingestion of a meal before or with alcohol is a common social situation which may complicate BAC estimation in some medico-legal cases. (C) 2010 Forensic Science Society. Published by Elsevier Ireland Ltd. All rights reserved.