Category: Pharmacology & Therapeutics
Keywords: nitroglycerin, hypotension, PDE5 inhibitors (PubMed Search)
Nitroglycerin is a potent vasodilator used most commonly for the treatment of angina and ACS. It can also be administered as a continuous infusion for acute management of a hypertensive emergency or sympathetic crashing acute pulmonary edema.
Most are aware of asking men for history of medications for erectile dysfunction (PDE5 inhibitors: sildenafil, tadalafil, vardenafil) but many overlook the fact that men and women may be on these medications chronically for pulmonary hypertension. Men can also be on these medications for the treatment of BPH. Be broad in your history taking and do not limit the discussion to erectile dysfunction or a specific gender.
-PDE5 inhibitors prevent the breakdown of cGMP
-Nitrates are nitric oxide donors that increase the production of cGMP
-The combination can lead to excessive vasodilation
If accidentally co-administered:
There is no antidote for this medication error. Support the patient with Trendelenburg positioning, fluid administration, and if needed, vasopressors such as norepinephrine until blood pressure stabilizes.
How long should you wait to administer nitrates after a patient takes a PDE5 Inhibitor?
Sildenafil and vardenafil: 24 h after last dose*
Tadalafil > 48 h after last dose*
*Even if acute ACS event
Schwartz BG, Kloner RA. Drug interactions with phosphodiesterase-5 inhibitors used for the treatment of erectile dysfunction or pulmonary hypertension. Circulation. 2010;122:88-95.