The interaction of sildenafil
(Viagra) and nitrates has resulted in protracted and profound
hypotension leading to death in some cases. An expert panel of the
More than 3,700 patients received sildenafil in controlled studies. Some had
cardiovascular disease but none were taking long-acting nitrates.
More than 3.6 million prescriptions have been filled. Of 69 reported
deaths, 21 were due to unknown causes, 2 to stroke, and 46 to
cardiovascular causes. Twelve deaths were possibly related to an
interaction between Viagra and nitrates. Although data are scarce,
the panel states that nitrates are contraindicated in patients who
have taken sildenafil in the previous 24 hours. The
interaction period is longer for patients with renal or hepatic
dysfunction or who are taking any drugs that inhibit or use the cytochrome P450 3A4 pathway (e.g., erythromycin and clotrimazole). In patients with acute coronary syndromes,
other anti-ischemic therapies should be used. Twenty-four hours
after sildenafil use, low-dose IV
nitroglycerin can be tried under full monitoring and with the
ability to provide fluid resuscitation and alpha agents.
Comment: There is evidence that physicians seek information
about sildenafil use infrequently before
initiating nitroglycerin therapy. Questioning patients is necessary
to avoid a potentially preventable bad outcome.
— JM Christenson
Published in Journal Watch Emergency Medicine July 1, 1999
Source
Chietlan MD et al. Use of Sildenafil (Viagra) in patients with cardiovascular
disease. J Am Coll Cardiol
1999 Jan 33 273-282