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 (ß) 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 22.5-42μg/100ml) and lowest after a meal (mean 21.4, range 13.5-32μg/100ml). T(max) was shortest after a meal and also remarkably consistent (mean 22, range 17-50min). 'Overshoot' was seen in most fasting subjects within about 40min of consuming alcohol. Elimination of alcohol from breath was slightly lower after a meal (mean 5.4, range 3.9-8.5μg/100ml/h) than after either fasting (mean 6, range 4.7-7.3μg/100ml/h) or a snack (mean 6, range 4.4-8.8μg/100ml/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.