Since antimuscarinics tend to delay gastric emptying they may alter the absorption of other medication given concomitantly.
Analgesics: increased risk of antimuscarinic side effects when antimuscarinics are given with nefopam. The absorption of paracetamol has been reported to be reduced and retarded.
Anti-arrhythmics: increased risk of antimuscarinic side effects with disopyramide.
Antidepressants: increased risk of antimuscarinic side effects when antimuscarinics are given with MAOIs or tricyclics or tricyclic-related antidepressants.
Antifungals: antimuscarinics reduce absorption of ketoconazole.
Antihistamines: increased risk of antimuscarinic side effects when antimuscarinics are given with antihistamines.
Anti-infectives: the absorption of nitrofurantoin has been reported to be enhanced.
Antimuscarinics: excessive muscarinic blockade may occur if Pro-Banthine is given concomitantly with belladonna alkaloids, synthetic and semi-synthetic antimuscarinic agents or other drugs with antimuscarinic activity.
Antipsychotics: antimuscarinics possibly reduce effects of haloperidol; increased risk of antimuscarinic side effects when antimuscarinics are given with clozapine; antimuscarinics reduce plasma concentration of phenothiazines, but risk of antimuscarinic side effects is increased.
Digoxin: concurrent use of Pro-Banthine with slow-dissolving tablets of digoxin may cause increased serum digoxin levels.
Domperidone: antimuscarinics antagonise effects of domperidone on gastrointestinal activity.
Dopaminergics: increased risk of antimuscarinic side effects when antimuscarinics are given with amantadine; antimuscarinics possibly reduce absorption of levodopa.
Memantine: effects of antimuscarinics possibly enhanced by memantine.
Metoclopramide: antimuscarinics antagonise effects of metoclopramide on gastrointestinal activity.
Nitrates: antimuscarinics possibly reduce effects of sublingual tablets of nitrates (failure to dissolve under tongue owing to dry mouth).
Parasympathomimetics; antimuscarinics antagonise effects of parasympathomimetics.