Ethanol elimination in the anesthetized dog: intragastric versus intravenous administration

We computed by linear kinetics predicted equilibrated plasma concentrations, elimination parameters and availability of ethanol for fasting anesthetized dogs who received the same dose (11 mmol/kg) of ethanol twice, once intragastrically and once intravenously. Agreement between predicted (y) and observed (x) equilibrated plasma levels above 3 mmol/l was for intragastric ethanol y = 0.031 + 1.008x (r = 0.973) and for intravenous ethanol y = 0.2 + 0.99x (r = 0.992). Linear elimination (elimination rate, clearance, time of disappearance of half the dose) was significantly slower and Widmark's ratio r was significantly greater for intragastric than for intravenous ethanol. Apparent availability of intragastric ethanol, computed by dividing the intragastric by the intravenous plasma ethanol concentration at zero time (both values extrapolated from the linear portion of the blood alcohol curve), was 0.739 +/- 0.125. Considerable ethanol residuals were present in the stomach four hours after intragastric instillation. We conclude that retention of ethanol in the stomach, probably because of anesthesia, created the apparent differences in elimination of ethanol between intragastric and intravenous administration. Despite gastric retention, decrease of ethanol levels was linear above 3 mmol/l after intragastric instillation.