Drug Interactions Newsletter

Volume 3, Issue 38, 10/11/2011

Question

How does the use of nitrates (nitroglycerin) in patients taking type 5 phosphodiesterase (PDE5) inhibitors, sildenafil (Viagra), tadalafil (Cialis), and vardenafil (Levitra) lower the blood pressure?

Answer

Nitroglycerin, regardless of the dosage form, is converted to nitric oxide (NO) once in the body.  It is commonly used in the treatment of angina (chest pain) in patients with underlying ischemic heart disease (IHD).  Since IHD can result in decreased coronary blood perfusion to the heart, the use of nitroglycerin can help vasodilate these vessels to increase coronary perfusion, thereby reducing the severity of angina.

Nitric oxide causes vasodilation through a combination of cellular processes.  The first is by....

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