Ethanol elimination rates at low concentrations based on two consecutive blood samples

Area of Science:

• Pharmacokinetics
• Forensic Toxicology
• Alcohol Metabolism

Background:

• Ethanol elimination kinetics transition from zero to first-order at low blood alcohol concentrations (BACs).
• Low BAC elimination in drunk drivers, particularly heavy drinkers with faster metabolism, is understudied.
• Understanding this transition is crucial for accurate legal and medical assessments.

Purpose of the Study:

• To determine the specific blood alcohol concentration (BAC) at which ethanol elimination kinetics shift from zero to first-order.
• To quantify ethanol elimination rates within very low BAC intervals in drunk drivers.
• To compare low BAC elimination rates in drunk drivers with reference populations.

Main Methods:

• Analysis of consecutively collected blood samples from suspected drunk drivers using headspace gas chromatography.
• Detailed study of elimination rates in a group with BACs below 0.25g/kg (n=175).
• Comparison with moderate (n=789) and high (n=4435) BAC reference groups.

Main Results:

• The shift from zero to first-order kinetics occurred below 0.19g/kg BAC.
• Above 0.19g/kg BAC, elimination rates were stable (0.18-0.19g/kg/h) and independent of concentration.
• Below 0.19g/kg BAC, elimination rates gradually declined and showed a strong positive correlation with concentration (r=0.56, p<0.001).

Conclusions:

• In drunk drivers, the transition to first-order ethanol elimination occurs below 0.19g/kg BAC.
• At BACs below 0.19g/kg, drunk drivers exhibit elimination rates similar to the general population.
• These findings can improve back-calculations in drunk driving cases involving low BACs.