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

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 ACC, ABAC and VBAC, respectively. The pseudo-zero-order elimination rate constant (beta) was 0.17 to 0.18, 0.21 to 0.22 and 0.26 to 0.27 g X 1(-1) X 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.

Comparison of ethanol concentrations in venous blood and end-expired breath during a controlled drinking study

“…These tests were probably made before alcohol was fully absorbed and distributed in all body fluids and when the arterial-venous differences in ethanol concentration was greatest [24,25]. The present study confirms that Intoxilyzer 5000S instrument almost always errs on the side of the suspect and in borderline cases this might make the difference between punishment or acquittal [20,28].…”

“…Moreover, BAC/BrAC ratios tended to be less than 2100 shortly after drinking ended during the absorption phase of ethanol kinetics increasing to 2300:1 in the first part of the postabsorptive phase and as low BACs were reached the BAC/ BrAC ratios increased further to reach 3000:1 or more [21]. A good explanation for these temporal variations in BAC/ BrAC ratio stems from the fact that concentrations of ethanol in breath more closely reflects the concentration-time course in arterial blood rather than venous blood which was the specimen analyzed in the present study and also used for forensic purposes [24,25].…”

“…Although, many studies have shown high correlations (r ¼ 0:95À0:98) between the concentrations of ethanol determined in blood and breath when specimens are taken nearly simultaneously, much less information exists about [18][19][20][21][22][23][24][25] the pharmacokinetics of ethanol derived from analyzing a series of breath samples [3,7]. The closeness of agreement between blood-and breath-alcohol concentration profiles during absorption, distribution and elimination stages of ethanol metabolism deserve further investigation.…”

Influence du site de prélèvement sur l’étude cinétique et métabolique de l’éthanol

“…Cette différence a déjà été décrite et étudiée pour l'éthanol [4,5], en particulier par l'équipe de Jones [6,7,9]. Dans notre étude, elle croît avec les doses, pour atteindre, à 20 min, plus de 1,6 g.L −1 pour la dose à 3 g.kg −1 .…”

“…Cette différence artérioveineuse a déjà été abondamment étudiée pour l'éthanol en raison de ses implications toxiques et légales [4][5][6][7][8][9]. Par contre, l'étude d'une différence artério-veineuse de la concentration sanguine de ses métabolites a fait l'objet de moins de publications [10,11].…”