The pharmacokinetics of alcohol in human breath, venous and arterial blood after oral ingestion

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Abstract
The concentration-time profile of ethanol in breath air (AAC), arterial (ABAC) and venous blood (VBAC) of human volunteers was studied after four different oral doses of absolute alcohol — 0.5, 0.75, 1.0, and 1.25 g/kg body weight. Seventy-eight single dose experiments were carried out in 42 subjects. In all 78 studies AAC was measured and VBAC was estimated simultaneously in blood collected from a cubital vein of 36 volunteers. Arterial blood, too, was collected from 8 subjects from a catheter in a brachial artery. All blood alcohol concentrations were analysed independently by gas chromatography (GLC) and an enzymatic (ADH) method. A one-compartment open model with first order absorption and pseudo-zero-order elimination was employed to calculate the pharmacokinetic parameters. The average values for the first order absorption rate constant (ka) ranged from 2.2 to 3.1, from 2.4 to 2.6 and from 1.0 to 1.7 h−1 for AAC, ABAC and VBAC, respectively. The pseudo-zero-order elimination rate constant (β) was 0.17 to 0.18, 0.21 to 0.22 and 0.26 to 0.27 g × 1−1 × h−1, respectively. During absorption ABAC tended to be higher than VBAC, peaking at a higher level (Cmax) and with a shorter time to peak (tmax) until an arterio-venous concentration equilibrium was reached, whereafter VBAC remained above ABAC. Although there was a close relationship between AAC, ABAC and VBAC during elimination, AAC closely followed the pattern of ABAC during absorption and tended to deviate from VBAC. AAC, therefore, is a much better predictor of ABAC during absorption than VBAC.