Academic journal article Alcohol Research

Alcohol and Medication Interactions

Academic journal article Alcohol Research

Alcohol and Medication Interactions

Article excerpt

Most people who consume alcohol, whether in moderate or large quantities, also take medications, at least occasionally. As a result, many people ingest alcohol while a medication is present in their body or vice versa. A large number of medications - both those available only by prescription and those available over the counter (OTC) - have the potential to interact with alcohol. Those interactions can alter the metabolism or activity of the medication and/or alcohol metabolism, resulting in potentially serious medical consequences. For example, the sedative effects of both alcohol and sedative medications can enhance each other (i.e., the effects are additive), thereby seriously impairing a person's ability to drive or operate other types of machinery.

Most studies assessing alcohol-medication interactions focus on the effects of chronic heavy drinking. Relatively limited information is available, however, on medication interactions resulting from moderate alcohol consumption (i.e., one or two standard drinks(1) per day). Researchers, physicians, and pharmacists must therefore infer potential medication interactions at moderate drinking levels based on observations made with heavy drinkers. In addition, moderate alcohol consumption may directly influence some of the disease states for which medications are taken (see sidebar, pp. 52-53, for further discussion of alcohol's influences on various disease states). This article discusses alcohol absorption, distribution, and metabolism within the body; the sites where potential alcohol-medication interactions can occur; and possible adverse effects from various alcohol-medication combinations, including OTC or herbal products.


Gastrointestinal Absorption and Metabolism

When alcohol is ingested through the mouth, a small amount is immediately broken down (i.e., metabolized) in the stomach. Most of the remaining alcohol is then absorbed into the bloodstream from the gastrointestinal tract, primarily the stomach and the upper small intestine. Alcohol absorption occurs slowly from the stomach but rapidly from the upper small intestine. Once absorbed, the alcohol is transported to the liver through the portal vein. A portion of the ingested alcohol is metabolized during its initial passage through the liver; the remainder of the ingested alcohol leaves the liver, enters the general (i.e., systemic) circulation, and is distributed throughout the body's tissues.

Alcohol metabolism (or the metabolism of any other substance) that occurs in the gastrointestinal tract and during the substance's initial passage through the liver is called "first-pass metabolism" [ILLUSTRATION FOR FIGURE 1 OMITTED]. For example, the mucosa lining the stomach contains enzymes that can metabolize alcohol as well as other substances; some of those enzymes, including alcohol dehydrogenase (ADH) and cytochrome P450 are described in more detail in the section "Alcohol Metabolism in the Liver."

The contribution of stomach (i.e., gastric) enzymes to first-pass alcohol metabolism, however, is controversial. Whereas some researchers have proposed that gastric enzymes play a major role in first-pass metabolism (Lim et al. 1993), other investigators consider the liver to be the primary site of first-pass metabolism (Levitt and Levitt 1998). Furthermore, some gender differences appear to exist in the overall extent of, and in the contribution of, gastric enzymes to first-pass metabolism. For example, the extent of first-pass metabolism is less in women than in men and some studies also have found lower gastric ADH activity in women (Thomasson 1995).

First-pass metabolism is readily detectable after consumption of low alcohol doses(2) that leave the stomach slowly (e.g., because they have been consumed with a meal). Thus, under such conditions of delayed gastric emptying, more alcohol can be metabolized in the stomach or absorbed slowly from the stomach and transported to the liver for first-pass metabolism. …

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