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Ethanol kinetics: extent of error in back extrapolation procedures.
Y al-Lanqawi1, T A Moreland, J McEwen
1Department of Pharmacology and Clinical Pharmacology, University of Dundee, Ninewells Hospital and Medical School, Dundee.
British Journal of Clinical Pharmacology
|October 1, 1992
Summary
Individual ethanol elimination rates vary significantly between people. Using a single average rate to calculate past blood alcohol levels can lead to substantial errors, highlighting the need for personalized pharmacokinetic assessments.
Area of Science:
- Pharmacokinetics
- Toxicology
- Human Physiology
Background:
- Ethanol elimination rate (k0) is crucial for determining blood alcohol concentrations.
- Significant inter-subject variability in ethanol kinetics is suspected.
- Accurate back-extrapolation of ethanol concentrations is vital for forensic and clinical applications.
Purpose of the Study:
- To assess the accuracy of back-extrapolating plasma ethanol concentrations using individual and population mean elimination rates.
- To quantify the variability and error associated with ethanol concentration back-extrapolation.
- To investigate the impact of extrapolation period length on accuracy.
Main Methods:
- 24 male volunteers received a single oral dose of ethanol (710 mg kg-1).
- Plasma ethanol concentrations were measured for 9 hours.
- Zero-order kinetics were assumed to back-extrapolate concentrations using individual and fixed k0 values.
Main Results:
- The mean ethanol elimination rate (k0) was 186 +/- 26 mg l-1 h-1.
- Back-extrapolation errors were small but highly variable, increasing with extrapolation period.
- Using a fixed population mean k0 (150 mg l-1 h-1) led to under-estimation, while a high individual k0 (238 mg l-1 h-1) caused over-estimation.
Conclusions:
- Substantial inter-subject variability in ethanol kinetics complicates accurate back-calculation of blood alcohol levels.
- A single, fixed slope value is insufficient for reliable ethanol concentration back-extrapolation.
- Personalized pharmacokinetic data is essential for minimizing errors in estimating past ethanol exposure.