Phosphodiesterase-5 and Nitrates
Phosphodiesterase-5 inhibitors may markedly increase the hypotensive effects of nitrates. Both nitrates and phosphodiesterase-5 inhibitors exert their effects by potentiating the vasodilatory effects of cyclic guanosine monophosphate, which is believed to be responsible for the hypotensive effects when these agents are administered concomitantly.
Phosphodiesterase-5 inhibitors are contraindicated in patients already receiving nitrates. However, 2013 guidelines for management of ST-segment elevation myocardial infarction and unstable angina/non-ST-segment elevation myocardial infarction published by the American College of Cardiology Foundation and American Heart Association support the administration of nitrates when medically necessary at least 24 hours after sildenafil (Viagra) or vardenafil (Levitra) or 48 hours after tadalafil (Cialis).
Am Fam Physician. 2019;99(9):558-564. © 2019 American Academy of Family Physicians