Drug Interaction Report

MONITOR: Beta-blockers may antagonize the cardiostimulatory effects of pressor agents by blocking beta-1 adrenergic receptors in the heart. Vasopressors may be less effective if the patient is receiving, or has recently received, a beta-blocking drug. In addition, peripheral vascular resistance may increase due to unopposed alpha-adrenergic effects of pressor agents in the presence of beta-blockade. Theoretically, the interaction may also occur with beta-blocker ophthalmic preparations, since they may be systemically absorbed and can produce clinically significant systemic effects even at low or undetectable plasma levels.

MANAGEMENT: No specific intervention is necessary, but clinicians should be alert to the potential for diminished cardiac response when pressor agents are used in patients treated with beta-blockers, including ophthalmic formulations. A beta-blocker such as propranolol may be used to treat cardiac arrhythmias that occur during administration of pressor agents like mephentermine, metaraminol, norepinephrine, or phenylephrine.

GENERALLY AVOID: Moderate-to-high dietary intake of potassium, especially salt substitutes, may increase the risk of hyperkalemia in some patients who are using angiotensin II receptor blockers (ARBs). ARBs can promote hyperkalemia through inhibition of angiotensin II-induced aldosterone secretion. Patients with diabetes, heart failure, dehydration, or renal insufficiency have a greater risk of developing hyperkalemia.

MANAGEMENT: Patients should receive dietary counseling and be advised to not use potassium-containing salt substitutes or over-the-counter potassium supplements without consulting their physician. If salt substitutes are used concurrently, regular monitoring of serum potassium levels is recommended. Patients should also be advised to seek medical attention if they experience symptoms of hyperkalemia such as weakness, irregular heartbeat, confusion, tingling of the extremities, or feelings of heaviness in the legs.

MONITOR: Coadministration of two or more sympathomimetic agents may increase the risk of adverse effects such as nervousness, irritability, and increased heart rate. Central nervous system (CNS) stimulants, particularly amphetamines, can potentiate the adrenergic response to vasopressors and other sympathomimetic agents. Additive increases in blood pressure and heart rate may occur due to enhanced peripheral sympathetic activity.

MANAGEMENT: Caution is advised if two or more sympathomimetic agents are coadministered. Pulse and blood pressure should be closely monitored.