PDE-5 inhibitors and nitroglycerin interactions: which statement is true?

• A. Sildenafil within 24 hours is safe
• B. Sildenafil and vardenafil within 24 hours are contraindicated
• C. Tadalafil within 24 hours is safe
• D. There is no interaction between PDE-5 inhibitors and nitroglycerin

Answer: (B)

PDE-5 inhibitors and nitrates share a dangerous interaction because both boost vasodilation through the NO–cGMP pathway. PDE-5 inhibitors prevent breakdown of cGMP, so nitric oxide from nitrates (like nitroglycerin) produces an exaggerated vasodilatory response. The result can be a severe drop in blood pressure, dizziness, syncope, and potentially ischemia in patients with heart disease.

Because of this, a nitrate-free window is required after taking a PDE-5 inhibitor. Sildenafil and vardenafil should not be given with nitroglycerin within 24 hours due to the risk of profound hypotension. Tadalafil has a longer duration of action, so the safe window is longer (not within 24 hours). There is indeed an interaction, and the statement that sildenafil and vardenafil within 24 hours are contraindicated is the true one.