Inhibited metabolism by ketoconazole, quinidine, itraconazole, erythromycin, fluoxetine. Reduced levels by rifampicin, phenytoin, carbamazepine, alcohol. Interfered w/ medications having anticholinergic activity. Synergistic activity w/ succinylcholine, other neuromuscular blockers or cholinergic agonists, β-blockers.