Nitrate therapy, Viagra don’t mix
Viagra is absolutely contraindicated in individuals receiving any form of nitrate therapy, emphasizes Odette Comeau-Luis, RN, MS, CCRN, coordinator of the Emergency Cardiac Care Center at Loma Linda (CA) University Medical Center and Children’s Hospital.
This includes all forms of nitrates: short-acting tablets or sprays, long-acting nitrates, nitroglycerin patches, pastes, and amyl nitrite or nitrate (also known as the recreational drug "poppers"), says Comeau-Luis.
Nitrates vasodilate along the same pathway that Viagra does, and so there is a marked potentiation of the vasodilatory effects when both medications are presents, notes Comeau-Luis.
Viagra potentiates the vasodilatory effect of circulating nitric oxide (nitrate mechanism of action), resulting in a significant and potential fatal fall in blood pressure, warns Clyde Miyagawa, PharmD, clinical pharmacy specialist in critical care at the University Hospital in Cincinnati. "Case reports have been reported of patients with cardiovascular disease taking nitrates who then take Viagra and have developed severe hypotension with consequent myocardial ischemic events."
Here are some management tips regarding Viagra and nitrate therapy, according to Comeau-Luis:
• The use of Viagra in the chest pain patient should be assessed prior to the administration of nitrates.
• Patients taking nitrates should be informed about the interaction between nitrates and Viagra, even if they have not asked for it, cautions Comeau-Luis. "There is the potential for obtaining Viagra from a friend or through the black market’ or other source."
• Caution and education is warranted in patients who only occasionally take nitrates and wish to try Viagra. The potential pitfall is the patient who develops chest pain after engaging in sexual activity and reaches for the nitroglycerin.
• Patients must be informed of the 24-hour time window in which interactions may occur.
It has been reported that when healthy volunteers were given Viagra followed by nitroglycerin one hour later, they experienced large decreases in systolic blood pressure (25mmHg to 51 mmHg) as well as diastolic blood pressure (up to 26 mmHg),1 Comeau-Luis notes. Other symptoms included light-headedness, headache, and nausea.
Decreased blood pressure with the use of nitrates may occur within 24 hours after a dose of Viagra.1
In patients who may have inadvertently received nitrates after using Viagra and are hypotensive, some recommendations include (depending on clinical indication; may be used alone or in combination):
— discontinue nitrate therapy;
— place the patient in Trendelenburg position;
— provide fluid resuscitation;
— provide intravenous-adrenergic agonist such as phenylephrine;
— provide an-and-adrenergic agonist (norepinephrine) for blood pressure support;
— provide intra-aortic balloon counterpulsation.
The mechanism of action of nitrates is the release of endogenous nitric oxide, notes Miyagawa. "Therefore, other agents that result in nitric oxide release can also result in this interaction, [i.e., nitroprusside]," he says. "Nitrates and nitroprusside should be avoided in patients who have recently taken a dose of sildenafil."
The most common scenario in the ED is a patient who takes a dose of sildenafil, and during sexual intercourse develops some cardiovascular compromise, says Miyagawa. "The patient is taken to the ER to rule out an MI and placed on nitroglycerin [IV or sublingual] for chest pain. This combination then can cause a potentially fatal fall in blood pressure."
Nurses should ascertain from patient or family members if sildenafil is being used prior to starting nitroglycerin or nitroprusside, he stresses.
Reference
1. Cheitlin M, Hunter A, Brintis R, et al. Use of Sidenafil (Viagra) in patients with cardiovascular disease. J Am Coll Cardiol 1999; 33:273-82.
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