Drug Interaction Report

Anticholinergic agents may increase the absorption and oral bioavailability of nitrofurantoin. The proposed mechanism involves increased gastrointestinal transit time due to reduction of stomach and intestinal motility by anticholinergic agents. In six healthy volunteers, pretreatment with propantheline 45 minutes before a single 100 mg dose of nitrofurantoin significantly increased the oral bioavailability of nitrofurantoin as indicated by a 68% increase in urinary recovery. In another study, atropine 500 mcg given subcutaneously one-half hour before a single 100 mg dose of nitrofurantoin delayed the absorption and urinary excretion of nitrofurantoin but did not affect its overall bioavailability in ten healthy volunteers. The clinical significance of these changes is unknown.

GENERALLY AVOID: Alcohol may potentiate some of the pharmacologic effects of CNS-active agents. Use in combination may result in additive central nervous system depression and/or impairment of judgment, thinking, and psychomotor skills.

MANAGEMENT: Patients receiving CNS-active agents should be warned of this interaction and advised to avoid or limit consumption of alcohol. Ambulatory patients should be counseled to avoid hazardous activities requiring complete mental alertness and motor coordination until they know how these agents affect them, and to notify their physician if they experience excessive or prolonged CNS effects that interfere with their normal activities.