Alpha/Beta Blockers

The final category of sympatholytic medications is alpha/beta blockers. These medications treat hypertension, as well as heart failure, in conjunction with digoxin, ACE inhibitors, and diuretics. Alpha/beta blockers have also been found to prolong clients’ chance of survival following a myocardial infarction (MI).

Prototype and Other Medications

The prototype medication for the alpha/beta blockers category is carvedilol. Another medication in this category is labetalol.

Expected Pharmacologic Action

Alpha/beta blockers act by blocking both alpha and beta receptors in the heart, arterioles, and kidney. Blocking the innervation of peripheral alpha₁ receptors causes dilation of the arterioles. Blocking the innervation of cardiac beta₁ receptors decrease the rate of the heart and its contractility. Blocking the innervation of kidney beta₁ receptors decreases the release of renin. Altogether, these actions cause decreased resistance in the blood vessels, decreased cardiac output, and increased excretion of water and sodium.

Adverse Drug Reactions

The side effects of alpha and beta blockers are similar to either one in isolation. Dizziness and hypotension, as well as bradycardia, may occur due to blockade of beta1 receptors in the heart. As stated earlier, blockade of beta1 receptors in the heart may lead to reduced cardiac output. Postural hypotension and exacerbation of asthma are also possible adverse drug reactions.

Interventions

Monitor the blood pressure of clients on alpha/beta blockers, and report hypotension to the provider. Also, monitor clients’ heart rate, and report to the provider a rate below 60 beats per minute or another pre-arranged parameter.

Safety Alert

Alpha/beta blockers, along with other medications that treat hypertension such as beta-adrenergic blockers, adrenergic neuron blockers, centrally acting alpha2 agonists, and cardiac glycosides can cause bradycardia. When administering one of these medications it is very important to check the client’s heart rate to make sure it is above 60 beats per minute. If it is not, giving the medication could drop the rate even more and actually cause a life-threatening bradycardia or heart block. Take the pulse apically for a full minute to ensure you get an accurate rate. If the client’s rate is below 60 beats per minute, hold the medication and notify the provider. If the rate is much lower than 60 beats per minute or the client is symptomatic, prepare to administer atropine and isoproterenol to increase the rate.

Administration

The prototype alpha/beta blocker, carvedilol, is available for oral use only. Give it with food to minimize orthostatic hypotension.

Client Instructions

Instruct clients who are taking an alpha/beta blocker to report dizziness or syncope to the provider. Reinforce the need to move slowly from a lying to a standing position to prevent falls. Remind them to avoid performing hazardous activities, such as driving, until they know the medication’s effects. Teach them how to check their pulse rate daily before taking their medication, and to report to the provider a pulse that is less than 60 beats per minute, or another parameter prearranged by the provider.

Contraindications and Precautions

Don’t give alpha/beta blockers to clients who have severe, unstable heart failure, asthma, or another type of bronchospastic disorder, heart block or severe bradycardia, or cardiogenic shock. They are also contraindicated in pregnancy and lactation. Use them with caution in children under the age of 18, and in clients with diabetes mellitus, renal or hepatic disorders, and peripheral vascular disease.

Interactions

The use of the prototype alpha/beta blocker, carvedilol, concurrently with insulin or an oral hypoglycemic will alter the effectiveness of the hypoglycemic medication. Dosages may need to be altered. Clients taking digoxin are at higher risk of bradycardia. Giving carvedilol with MAO inhibitor antidepressants can cause bradycardia or hypotension. Cimetidine can increase the blood levels of alpha/beta blockers, and their use with other antihypertensive medications may increase clients’ risk for hypotension. For an overview of the alpha-beta blocker prototype medication, click on the button below to access a medication information table.