Requests for estimates of blood alcohol concentrations (BACs) are often made when blood samples are taken some hours after the time of interest. Many believe that such estimates are not reliable because the subject's alcohol clearance rate is never known and often there is uncertainty as to whether the subject was postabsorptive at the time in question. In order to evaluate the potential errors associated with BAC estimates under these non-ideal conditions, BAC estimates were compared with empirical data obtained from 24 healthy males, ranging in age from 22 to 56 years, who took part in a three hour social drinking session. One blood sample for alcohol analysis was taken from each subject approximately 1 hour after drinking stopped and another was taken approximately 3.5 hours after drinking stopped. Estimations of BACs at the blood sampling time points were made assuming each person had a constant blood alcohol clearance rate in the range of 10 to 20 mg/dL/h (0.01 to 0.02 g/dL/h) over the whole of the experimental period. A variety of methods were used to estimate the volume of distribution for alcohol. All BAC estimations were made assuming complete absorption and full equilibration of the total alcohol dose. The results showed that actual BACs were usually within or very close to the range of “forward” estimates based on the known alcohol doses. Furthermore, most BACs measured about an hour after cessation of drinking were within or very close to the predicted range based on back extrapolation from the actual 3.5 hour BAC result.

Blood alcohol concentrations (BAC) and corresponding breath alcohol concentrations (BrAC) were determined for 21,582 drivers apprehended by New Zealand police. BAC was measured using headspace gas chromatography, and BrAC was determined with Intoxilyzer 5000 or Seres Ethylometre infrared analysers. The delay (DEL) between breath testing and blood sampling ranged from 0.03 to 5.4 h. BAC/BrAC ratios were calculated before and after BAC values were corrected for DEL using 19 mg/dL/h as an estimate of the blood alcohol clearance rate. Calculations were performed for single and duplicate breath samples obtained using the Intoxilyzer (groups I-1 and I-2) and Seres devices (groups S-1 and S-2). Before correction for DEL, BAC/BrAC ratios for groups I-1, I-2, S-1, and S-2 were (mean+/-SD) 2320+/-260, 2180+/-242, 2330+/-276, and 2250+/-259, respectively. After BAC values were adjusted for DEL, BAC/BrAC ratios for these groups were (mean+/-SD) 2510+/-256, 2370+/-240, 2520+/-280, and 2440+/-260, respectively. Our results indicate that in New Zealand the mean BAC/BrAC ratio is 19-26% higher than the ratio of the respective legal limits (2000).

A study was undertaken to examine the relationship between blood acetaldehyde levels and clinical responses in volunteers receiving the anti-alcohol drugs disulfiram and calcium cyanamide. In the first part of this study volunteers received different doses of disulfiram (125 mg and 500 + 250 mg), of calcium cyanamide (25 mg, 50 mg and 100 mg) and of ethanol (0.2 g/kg orally and 0.5 g/kg intravenously). The ensuing interactions ranged from no reaction at all to an intense hypotensive cyanamide-ethanol reaction (CER). A blood acetaldehyde concentration-effect relationship was suggested. In the second part of this study seven subjects received 50 mg of calcium cyanamide 4 hr prior to an intravenous ethanol dose of 0.2 g/kg. The maximum blood level of acetaldehyde ranged from 16 to 241 microM. Aversive interactions started to occur at acetaldehyde levels around 40-60 microM. Changes in flushing reaction and diastolic blood pressure appeared best to reflect changing blood acetaldehyde levels. As a rule, however, the expected cyanamide-ethanol and disulfiram-ethanol reactions are more clearly registered as an increase in acetaldehyde levels than as the ensuing physiological responses.

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4-methylpyrazole (4-MP), an inhibitor of alcohol dehydrogenase, rapidly abolished the accumulation of acetaldehyde following alcohol ingestion both in volunteers pretreated with the Antabuse analog calcium carbimide and in an antabuse-treated alcoholic. 4-MP also attenuated other typical symptoms, including facial flushing and tachycardia, thus suggesting its usefulness in the acute treatment of severe disulfiram-alcohol reactions.