Abstract
According to the theoretical pharmacokinetical considerations put forward by Wehner et al. the BACven/BrAC conversion factor Q is not a constant value and varies depending on the pharmacokinetic phase deduced from the alcohol concentration curve. Based on these considerations we propose that Q must be inversely proportional to the BrAC during the postabsorptive linear elimination phase, expressed as the hyperbola Q=1/κ+(CT)/BrAC. The constants κ or 1/κ and (CT)—where (CT) consists of different parameters which remain constant during the linear elimination phase—can be experimentally determined from the linear relationship BrAC=κBACven−κ(CT). To test this hypothesis 12 human volunteers received parenteral doses of ethanol. During the elimination phase, BAC and BrAC of each volunteer were measured between 18 and 34 times in a BrAC range between 0.65 mg/l and 0.12 mg/l. The conversion factor Q was either expressed in the form of the hyperbola Q=1/κ+(CT)/BrAC or directly calculated from the ratio BACven/BrAC and the results obtained using both methods were found to be very similar. The values of 1/κ of the hyperbolic functions varied between 1.808 and 2.165 and those of (CT) between 0.004 and 0.127. For a BrAC of 0.25 mg/l, an average value of 2.308±0.080 could be calculated for the conversion factor Q0.25. On average, the value of Q0.40 amounted to 2.207±0.048 and that of Q0.55 to 2.160±0.056.
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H.T. Haffner and M. Graw have contributed equally to the manuscript.
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Haffner, H.T., Graw, M., Dettling, A. et al. Concentration dependency of the BAC/BrAC (blood alcohol concentration/breath alcohol concentration) conversion factor during the linear elimination phase. Int J Legal Med 117, 276–281 (2003). https://doi.org/10.1007/s00414-003-0384-5
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DOI: https://doi.org/10.1007/s00414-003-0384-5