Interactions between alcohol and cardiovascular medications

Alcohol Health & Research World, Summer, 1990 by Barbara A. Thomas, Timothy J. Regan

It is interesting to note that a drug [digitalis] whose use in even moderately large doses is supposed to be fraught with some danger, can be given in one-half-ounce doses [to alcoholics] without producing any of the ordinary symptoms of digitalis poisoning (p. 337).

A possible explanation for this puzzling effect of alcohol on digitalis was found years later. Frey and Vallee (1979) determined that digitalis is metabolized by alcohol dehydrogenase, the principal enzyme involved in alcohol metabolism.

Alcohol influences the body in many ways that can modify the effects of medications. Alcohol can affect the gastrointestinal absorption, hepatic metabolism (metabolism in the liver), serum protein binding (binding to proteins in blood), and urinary excretion of a medication. Several factors can modify the nature of alcohol interactions. Generally, alcohol at low blood-levels will interact with other substances differently than will alcohol at high blood-levels; however, precise and predictable correlations have not been established. Interactions also depend on the amount of time between alcohol intake and administration of the medication. Kupari and colleagues (1984) found that alochol consumed 1 hour before taking nitroglycerin enhanced the medication's blood-pressure-lowering effect. However, alcohol consumed just before taking nitroglycerin did not lead to an enhanced effect.

Finally, the intensity and chronicity of a subject's drinking habits affect alcohol-medication interactions. Many of the medications with which alcohol interacts are processed in the liver by the same enzymes that process alcohol, and therefore compete with alcohol for processing. Alcohol has a competitive advantage in this regard, however, because it is ingested in much larger amounts. Chronic use of alcohol leads to increased production of alcohol-processing enzymes, which means that more alcohol can be processed. This also means that greater amounts of other substances normally handled by such enzymes can also be processed, especially when alcohol is not present in the blood. This is one reason why alcohol-medication interactions vary widely in occasional drinkers, in chronic heavy drinkers, and in abstinent alcoholics.

INTERACTIONS WITH SPECIFIC

CARDIOVASCULAR MEDICATIONS

It is convenient to arrange a discussion of interactions between alcohol and cardiovascular medications according to their use in cardiology practice. (1) Inotropic medications, which improve the contraction of the heart, are used to treat cardiac insufficiency or failure. (2) Antianginal medications, which cause the coronary blood vessels supplying the heart tissue to dilate, thereby increasing the myocardial blood supply, are given for cardiac chest pain, or angina. (3) Antiarrhythmics slow a rapid heart rate (tachycardia, flutter, fibrillation) or regularize an irregular heartbeat. (4) Antihypertensives lower blood pressure. (5) Anticoagulant and platelet-inhibiting medications impede, respectively, clot formation and thrombus formation.