LETTERS TO THE EDITORS
The Correct Dosage
To the Editors:
Robert S. Gable's essay "The Toxicity of Recreational
Drugs" (Macroscope, May-June) provides information
that has significant societal relevance at the present time. I
would, however, point out that Dr. Gable's determination of the
ethanol (ethyl alcohol, or "alcohol") content of several
beverages is inaccurate.
Specifically, Dr. Gable says that "approximately 33 grams of
ethyl alcohol" would allow a normal, healthy 70-kilogram adult
to "achieve a relaxed affability." He adds, "This
effective dose can come from two 12-ounce beers, two 5-ounce glasses
of wine or two 1.5-ounce shots of 80-proof vodka." I assume
that fluid ounces are intended in these measurements. Of these three
beverages, the only one whose alcohol concentration is specified is
vodka, which at 80 proof contains 40 percent alcohol by volume, or
40 milliliters of alcohol per 100 milliliters of vodka.
The number of grams of alcohol in two 1.5-fluid ounce shots of vodka
is essentially 28 grams, about 15 percent less than the 33 grams
reported by Dr. Gable. The amount can be calculated using
dimensional analysis, or the unit-factor method, as shown in the
diagram below. In this calculation, the units of fluid ounces (fl
oz) of vodka, milliliters (mL) of vodka, and mL alcohol
"cancel" each other via the operation of division, so that
the desired unit of grams (g) of alcohol" remains.
Similar calculations for two 12-fluid-ounce beers containing five
percent alcohol by volume (or 0.05 milliliters of alcohol per 1
milliliter of beer) and two 5-fluid-ounce glasses of wine containing
12 percent alcohol by volume (or 0.12 milliliters of alcohol
per 1 milliliter of wine) yield 28 grams of alcohol as well.
I would submit that the "effective dose" of approximately
33 grams of alcohol specified by Dr. Gable would be obtained from
approximately 2.4 shots of vodka at 1.5-fluid ounces each, 2.4 beers
at 12 fluid ounces each or 2.4 glasses of wine at 5 fluid ounces
each. Therefore, approximately 24 shots of vodka would be nearly
equivalent to the 330-gram median lethal dose of alcohol cited by
I would emphasize that the quantitative fine-tuning of Dr. Gable's
presentation that is offered here does not minimize the timely
message of his essay.
Dominick A. Labianca
The City University
of New York
Dr. Gable responds:
Dr. Labianca's "quantitative fine-tuning," as he described
his comments, provides a valuable opportunity to emphasize the
variability in ethanol content among common alcohol beverages. My
statement that "approximately 33 grams of ethyl alcohol
… can come from two 12-ounce beers, two 5-ounce glasses of
wine, or two 1.5-ounce shots of 80-proof vodka" was a rough
approximation. Dr. Labianca's letter, noting that the 80-proof vodka
will yield only 28 grams (not 33 grams) of alcohol, is gratefully
received, and I regret my imprecision.
However, in my view, 33 grams of alcohol is not an unreasonable
general estimate for two containers of beer or malt beverage. Many
of these drinks have alcohol greater than the 5 percent by volume
that I mentioned as a sample in my article. The published range of
alcohol concentration for theses beverages is 2.92 to 15.66 percent.
Wine is often over 12 percent. The commonly seen label for table
wine that states "alcohol 12.5% by volume" can legally
represent a range from 11 to 14 percent. The legal range for
sherries is 17 to 20 percent. Thus, the alcohol in these beverages,
for the quantities I mentioned, can be considerably greater than 33 grams.
Given the variability within various categories of legal alcohol
beverages, users of illicit substances should be even more wary of a
potential overdose. Dr. Labianca's letter has usefully prompted
attention to this hazard.