Drug Interaction Report

ADJUST DOSING INTERVAL: Anticholinergics, beta-agonists, and theophylline may inhibit the bronchial airway response to methacholine. Methacholine is a cholinergic agonist that binds muscarinic receptors in bronchial smooth muscle, which leads to bronchoconstriction. Since patients with asthma exhibit greater sensitivity to induced bronchoconstriction than healthy subjects, methacholine is used to diagnose bronchial airway hyperreactivity in the absence of clinically apparent asthma. Bronchodilation caused by anticholinergics, beta-agonists, and theophylline may counteract methacholine-induced bronchoconstriction, possibly leading to diagnostic failure.

MANAGEMENT: Treatment with anticholinergics, beta-agonists, and theophylline should be interrupted before methacholine administration for the following durations:
--Short-acting anticholinergics (e.g., ipratropium): 12 hours
--Long-acting anticholinergics (e.g., tiotropium): At least 168 hours
--Short-acting beta-agonists (e.g., albuterol): 6 hours
--Long-acting beta-agonists (e.g., salmeterol): 36 hours (some authorities recommend 48 hours for ultra-long-acting beta-agonists [e.g., indacaterol, olodaterol, vilanterol])
--Oral theophylline: 12 to 48 hours

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.