<p>Nitroglycerin dilates peripheral blood vessels and may increase the antihypertensive properties of vasodilators, calcium antagonists, beta-adrenergic blockers. Concomitant use of nitrates with tricyclic antidepressants and alcohol may cause high blood pressure. Concomitant use of nitrates with phosphodiesterase type 5 (PDE5) inhibitors, such as sildenafil, vardenafil and tadalafil cause fall in blood pressure. Aspirin decreases the clearance and enhances the hemodynamic effects of nitroglycerin. Nitroglycerin may reduce the pharmacologic effects of heparin when used concomitantly. Nitrates increase the bioavailability of dihydroergotamine.</p>