Glutethimide, phenobarb, phenytoin, carbamazepine, rifampicin, alcohol abuse, long-term use of paracetamol, concomitant use of paracetamol & zidovudine, probenecid, cholestyramine, tri- & tetracyclic antidepressants, antihistamines, antipsychotics, quinidine, amantadine, tiotropium, ipratropium, atropine-like compd, metoclopramide, β-adrenergics.