The anticholinergic activity of oxybutynin is increased by concurrent use of other anticholinergics or drugs with anticholinergic activity, such as amantadine and other anticholinergic antiparkinsonian drugs (e. g. biperiden, levodopa), antihistamines, antipsychotics (e. g. phenothiazines, butyrophenones, clozapine), quinidine, tricyclic antidepressants, atropine and related compounds like atropinc antispasmodics, dipyridamole.