Alcohol (beverage ethanol) has diverse and widespread effects on the body, and impacts directly or indirectly on almost every neurochemical system in the brain. A large majority of patients in most clinical settings consume alcohol, with the highest proportions of drinkers of at least modest levels of alcohol seen in more educated and affluent patient groups. At even relatively low doses, this drug can exacerbate most medical problems and affect medications metabolized in the liver, and at higher doses can temporarily mimic many medical (e.g., diabetes) and psychiatric (e.g., depression) conditions. The lifetime risk for repetitive serious alcohol problems (e.g., alcohol use disorders as described below) in patients is about 20% for men and 10% for women, regardless of a person’s education or income. Although low doses of alcohol might have healthful benefits, greater than three standard drinks per day enhances the risk for cancer and vascular disease, and alcohol use disorders decrease the life span by about 10 years. Unfortunately, most clinicians have had only limited training regarding identifying and treating alcohol-related disorders. This chapter presents a brief overview of clinically useful information about alcohol use and associated problems.
PHARMACOLOGY AND NUTRITIONAL IMPACT OF ETHANOL
Ethanol blood levels are expressed as milligrams or grams of ethanol per deciliter (e.g., 100 mg/dL = 0.10 g/dL), with values of ~0.02 g/dL resulting from the ingestion of one typical drink. In round figures, a standard drink is 10–12 g, as seen in 340 mL (12 oz) of beer, 115 mL (4 oz) of nonfortified wine, and 43 mL (1.5 oz) (a shot) of 80-proof beverage (e.g., whisky); 0.5 L (1 pint) of 80-proof beverage contains ~160 g of ethanol (about 16 standard drinks), and 750 mL of wine contains ~60 g of ethanol. These beverages also have additional components (congeners) that affect the drink’s taste and might contribute to adverse effects on the body. Congeners include methanol, butanol, acetaldehyde, histamine, tannins, iron, and lead. Alcohol acutely decreases neuronal activity and has similar behavioral effects and cross-tolerance with other depressants, including benzodiazepines and barbiturates.
Alcohol is absorbed from mucous membranes of the mouth and esophagus (in small amounts), from the stomach and large bowel (in modest amounts), and from the proximal portion of the small intestine (the major site). The rate of absorption is increased by rapid gastric emptying (as seen with carbonation); by the absence of proteins, fats, or carbohydrates (which interfere with absorption); and by dilution to a modest percentage of ethanol (maximum at ~20% by volume).
Between 2% (at low blood alcohol concentrations) and 10% (at high blood alcohol concentrations) of ethanol is excreted directly through the lungs, urine, or sweat, but most is metabolized to acetaldehyde, primarily in the liver. The most important pathway occurs in the cell cytosol where alcohol dehydrogenase (ADH) produces acetaldehyde, which is then rapidly destroyed by aldehyde dehydrogenase (ALDH) ...