CLARINASE 24Hr Tablets are contraindicated in those who have shown sensitivity or idiosyncrasy to their components or to adrenergic agents. CLARINASE 24Hr Tablets also are contraindicated in patients receiving MAO inhibitor therapy or within two weeks of discontinuing such treatment and in patients with narrow angle glaucoma, urinary retention, severe hypertension, severe coronary artery disease and hyperthyroidism.