Drug Interaction Report

MONITOR: Coadministration with beta-2 adrenergic agonists may potentiate the hypokalemic effects of potassium-wasting diuretics. Beta-2 agonists can cause clinically significant but usually transient decreases in serum potassium concentrations. Since QT prolongation is a possible side effect of beta-2 agonists, exacerbation of hypokalemia may increase the risk of torsade de pointes and other serious arrhythmias. The interaction may be more likely with systemic or nebulized formulations of beta-2 agonists, high dosages of inhaled beta-2 agonists, or concomitant theophylline or corticosteroid therapy.

MANAGEMENT: Caution is advised when beta-2 agonists are used with potassium-wasting diuretics. Serum potassium level and cardiovascular status should be monitored, especially if the beta-2 agonist is administered systemically or by nebulizer. Patients should be advised to notify their physician if they experience potential signs and symptoms of hypokalemia such as fatigue, weakness, myalgia, muscle cramps, numbness, tingling, abdominal pain, constipation, palpitation, and irregular heartbeat.

GENERALLY AVOID: Use of anticholinergic agents with alcohol may result in sufficient impairment of attention so as to render driving and operating machinery more hazardous. In addition, the potential for abuse may be increased with the combination. The mechanism of interaction is not established but may involve additive depressant effects on the central nervous system. No effect of oral propantheline or atropine on blood alcohol levels was observed in healthy volunteers when administered before ingestion of a standard ethanol load. However, one study found impairment of attention in subjects given atropine 0.5 mg or glycopyrrolate 1 mg in combination with alcohol.

MANAGEMENT: Alcohol should generally be avoided during therapy with anticholinergic agents. Patients should be counseled to avoid activities requiring mental alertness until they know how these agents affect them.