Safety of intravenous nitroglycerin after administration of sildenafil citrate to men with coronary artery disease: A double-blind, placebo-controlled, randomized, crossover trial*

OBJECTIVE: Although contraindicated, there are situations when a patient who has recently taken a phosphodiesterase 5 inhibitor (e.g., sildenafil) might need intravenous nitroglycerin (NTG) treatment. This study determined if, and at what dose, intravenous NTG could be administered safely to men with coronary artery disease who had recently ingested sildenafil. DESIGN: Double-blind, placebo-controlled, randomized, crossover trial. SETTING: Four clinical practice sites in Canada, Scotland, and the United States. PATIENTS: A total of 34 men (>or=35 yrs) with a history of angina pectoris and coronary artery disease (>50% stenosis of at least one coronary artery), most of whom were taking antihypertensives. INTERVENTIONS: Sildenafil (100 mg) or placebo (single dose; crossover after 3-7 days) followed 45 mins later by escalating doses of intravenous NTG (160 microg/min maximum). MEASUREMENTS AND MAIN RESULTS: After sildenafil, there were slightly greater maximum (supine) blood pressure decreases and heart rate increases (e.g., 4 to 6 mm Hg [systolic] and <or=1 beat/min, at NTG doses of <or=80 microg/min) than after placebo. The median maximum tolerated NTG dose (range) was 80 (0-160) microg/min for sildenafil vs. 160 (20-160) microg/min for placebo (adjusted mean +/- se, 77 +/- 7 vs. 127 +/- 7; p < .0001; analysis of variance), and NTG 160 microg/min was tolerated by eight (25%) and 19 (59%) men, respectively (p = .0008). Treatment-related adverse events were mostly mild/moderate hypotension, headache, and dizziness, which are often associated with NTG alone. Sildenafil and metabolite plasma concentrations were lower than previously reported in healthy men. CONCLUSIONS: With close monitoring of blood pressure and heart rate, men with stable coronary artery disease who have taken sildenafil may tolerate intravenous NTG (<or=160 microg/min) with low starting dosage and gradual upward titration. The hemodynamic response might be different in subgroups not specifically examined in the study (e.g., men presenting with acute coronary symptoms). The explanation for the lower than expected plasma concentrations remains uncertain.