The 2-carbon alcohol ethanol (CH3CH2OH), or beverage alcohol, is one of the most versatile drugs known to man, with multiple direct effects on a diverse range of neurochemical systems. Produced in nature, rewarding in its effects, and easy to manufacture, it has been taken by humans since the beginning of recorded history, is consumed by a large majority of people in the Western world, and is likely to contribute to more morbidity, mortality, and public health costs than all of the illicit drugs combined.
ETHANOL CONSUMPTION. Compared with other drugs, surprisingly large amounts of alcohol are required for physiological effects, resulting in its consumption more as a food than a drug. The alcohol content of beverages typically ranges from 4-6% (volume/volume) for beer, 10-15% for wine, and 40% and higher for distilled spirits (the "proof" of an alcoholic beverage is twice its percentage of alcohol; e.g., 40% alcohol is 80 proof). A glass of beer or wine, a mixed drink, or a shot of spirits contains ~14 g alcohol, or ~0.3 mol ethanol. Thus, alcohol is consumed in gram quantities, whereas most other drugs are taken in milligram or microgram doses.
Because the ratio of ethanol in end-expiratory alveolar air and ethanol in the blood is relatively consistent, blood ethanol concentrations (BECs) in humans can be estimated readily by the measurement of alcohol levels in expired air; the partition coefficient for ethanol between blood and alveolar air is approximately 2000:1. Because of the causal relationship between excessive alcohol consumption and vehicular accidents, there has been a near-universal adoption of laws attempting to limit the operation of vehicles while under the influence of alcohol. Legally allowed BECs in the U.S. typically are set at or below 80 mg% (80 mg ethanol per 100 mL blood; 0.08% w/v), which is equivalent to a concentration of 17 mM ethanol in blood. A 12-oz bottle of beer, a 5-oz glass of wine, and a 1.5-oz "shot" of 40% liquor each contains approximately 14 g ethanol, and the consumption of 1 of these beverages by a 70-kg person would produce a BEC of ~30 mg%. However, it is important to note that this is approximate because the BEC is determined by a number of factors, including the rate of drinking, gender, body weight and water percentage, and the rates of metabolism and stomach emptying (see "Acute Ethanol Intoxication" later in the chapter).
ABSORPTION. After oral administration, ethanol is absorbed rapidly into the bloodstream from the stomach and small intestine and distributes into total-body water (0.5-0.7 L/kg). Peak blood levels occur about 30 min after ingestion of ethanol when the stomach is empty. Because absorption occurs more rapidly from the small intestine than from the stomach, delays in gastric emptying (owing, e.g., to the presence of food) slow ethanol absorption. Because of ...