Interactions between alcohol and cardiovascular medications

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

activity of propranolol (Grabowski et al. 1980).

Atenolol

Atenolol is a beta-adrenergic blocking medication used in the treatment of high blood pressure and chronic stable angina. Guevara (1983) found that in nonalcoholic hypertensive patients treated with atenolol, alcohol contributed significantly to the lowering of arterial blood pressure, probably because of additive effects of alcohol and atenolol.

Filipek and colleagues (1989a) conducted a study using rats to examine the effect of alcohol on the antiarrhythmic action of atenolol. Concurrent administration of alcohol and atenolol led to inhibition of atenolol's antiarrhythmic effect at lower doses (of atenolol). At higher doses of atenolol, alcohol inhibition was not apparent. When rats were fed alcohol for 5 days previously, the effects of alcohol on atenolol's antiarrhythmic effect were similar at low doses of atenolol. However, the highest dose of atenolol produced an antiarrhythmic effect that was actually stronger than that expected in a case without alcohol. Moreover, animal mortality increased. Although these results may not be applicable to humans, care should be exercised when prescribing or using atenolol.

Verapamil

Verapamil is a calcium channel blocker; that is, a medication that impedes the flow of calcium ions into the muscle cells of the heart and blood vessels. Interference with the calcium ion flow lessens cardiac contractility, which weakens the force of the heartbeat, and leads to dilation of the blood vessels, and, generally, to lower blood pressure.

Verapamil is used as a vasodilator in the treatment of angina and, occasionally, in the treatment of high blood pressure. It also has antiarrhythmic effects and is used to treat rapid heart-beat. The antiarrhythmic effect of verapamil was studied by Posner and colleagues (1986) using tissue samples from the sinoatrial nodes and atria of rats who were fed either sucrose or alcohol. The researchers found that verapamil slowed the rate of electrical discharge in tissues taken from the alcohol-fed rats more than in tissues taken from sucrose-fed rats. These experimental findings suggest that the use of alcohol with verapmail will enhance verapamil's heart-rate-slowing effect.

ANTIHYPERTENSIVE MEDICATIONS

High blood pressure, or hypertension, is treated with several types of medications, most of which are used to treat other cardiovascular disorders as well. Alcohol produces effects similar to those of diuretics, which stimulate the production of urine, and vasodilators, which dilate blood vessels. The net effects of alcohol's interactions with these types of medications is probably negligible. Adrenergic-inhibiting medications, which counteract activities of various types of adrenergic receptors, may produce stronger interactions with alcohol. The beta-adrenergic blockers were discussed earlier; we therefore limit the following discussion to three other inhibitors, clonidine, guanethidine, and reserpine.

Clonidine

Clonidine lowers blood pressure by acting on adrenergic receptors located in the brainstem. Alcohol and clonidine are physiologic antagonists (Abdel-Rahman 1989): clonidine depresses activity in the central sympathetic nervous system (the brain and spinal cord), whereas alcohol enhances sympathetic activity. Also, clonidine increases reflex heart rate in response to signals originating from pressure sensors, whereas alcohol impairs this reflex response.