Drug Interaction Report

MONITOR: Theoretically, anticholinergic agents and other agents with significant anticholinergic activity (e.g., antihistamines, antispasmodics, neuroleptics, phenothiazines, skeletal muscle relaxants, tricyclic antidepressants, class IA antiarrhythmics especially disopyramide) may antagonize the effects of topically administered cholinergic agents such as acetylcholine, carbachol, demecarium, echothiophate, isoflurophate, physostigmine, and pilocarpine. The proposed mechanism involves opposing pharmacodynamic action on muscarinic receptor sites in ocular tissue. This interaction is sometimes desirable and is the basis for using atropine in the treatment of excessive muscarinic side effects and cholinergic crisis induced by cholinergic overdose.

MANAGEMENT: Patients receiving long-term therapy with anticholinergic agents should be monitored for potentially diminished therapeutic (miotic) response to ophthalmic cholinergic therapy, and dosages adjusted as necessary.

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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.

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