Interactions between alcohol and cardiovascular medications

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

The manifestations of interactions between alcohol and cardiovascular medications depend on the condition for which the patient is being treated, the seriousness of that condition, and the amount of alcohol consumed or otherwise taken into the body. A patient being treated for mild hypertension may perceive no effect after consuming alcohol, whereas a patient being treated for heart failure or arrhythmia may experience a life-threatening situation as a result of even moderate alcohol consumption.

INOTROPIC MEDICATIONS

A heart functioning normally beats at an adequate rate and contracts forcefully and in a synchronized manner to propel the blood through the cardiac cavities and the circulatory system. Inotropic medications are used to enhance the heart's ability to contract at times when that ability has become impaired, such as when the heart's cavities have become enlarged and during heart failure.

Some of the most frequently prescribed inotropic medications are digitalis glycosides. Digoxin and digitoxin are used in the treatment of heart failure and in some supraventricular rhythm disorders. These two medications regulate heartbeat and improve the heart's ability to contract. Frey and Vallee (1979) found that alcohol dehydrogenase, the major alcohol-metabolizing enzyme, oxidizes, in vitro, the pharmacologically active metabolites of digoxin and digitoxin. The researchers determined that these metabolites compete with alcohol for the same binding sites on the enzyme. (Substances must bind to an enzyme before they can be metabolized by it.)

Although digitalis is relatively toxic, there have been no clinical reports of an alcohol-digitalis interaction, other than the mention by Limas and co-workers (1974) that ouabain (another digitalis glycoside) failed to improve ventricular function in seven alcoholics with cirrhosis. It may be prudent to select a nondigitalis medication for the treatment of cardiac failure in alcoholics or abstinent alcoholics.

ANTIANGINAL MEDICATIONS

The heart, like all tissues of the body, must receive an adequate supply of blood. When the blood supply to the heart muscle is inadequate--a condition known as ischemia--minor damage occurs, accompanied by pain, or angina. If the insufficiency intensifies, the heart muscle will die, which is essentially what occurs during a heart attack. Organic nitrates and nitrites have the double effect of increasing the blood supply to the heart muscle and also reducing myocardial oxygen consumption, both of which help alleviate angina. These medications increase the blood supply by relaxing the smooth muscles layer of blood vessels, particularly coronary vessels, but also systemic vessels. Myocardial oxygen consumption declines as the cardiac workload lessens in response to peripheral vasodilation.

Nitroglycerin is a commonly prescribed organic nitrate. In studies of alcohol-nitroglycerin interactions, healthy subjects taking nitroglycerin and alcohol were found to have significantly lower maximum (systolic) blood pressure and ventricular wall stress than did healthy subjects taking nitroglycerin and not alcohol (Kupari et al. 1984). Alcohol enhances the blood-pressure-lowering action of nitroglycerin, sometimes dangerously, as in the case of the 71-year-old patient cited earlier.