Pharmacological interactions Caution should be exercised in coadministration of fesoterodine with other antimuscarinic agents and medicinal products with anticholinergic properties (e. g. amantadine, tri-cyclic antidepressants, certain neuroleptics) as this may lead to more pronounced therapeutic- and side-effects (e. g. constipation, dry mouth, drowsiness, urinary retention).