CriticalOrganic nitrate×Phosphodiesterase type 5 inhibitors (PDE5)
Updated · Methodology
Mechanism
Sildenafil blocks phosphodiesterase-5, slowing breakdown of cGMP – the intracellular mediator of vascular relaxation. Nitroglycerin raises cGMP production. Co-administration sharply amplifies vasodilation – severe systemic hypotension develops. Fatal cases have been reported.
Symptoms
Sudden drop in blood pressure: dizziness, visual greying, syncope, shock. In ischaemic heart disease, risk of myocardial infarction from coronary perfusion collapse.
Management
The combination is not prescribed. After sildenafil, nitrates are permitted only after 24 hours. After tadalafil (long-acting), only after 48 hours. In acute coronary syndrome after recent sildenafil, replace nitrates with morphine and oxygen; for preload reduction, use furosemide.
Check the full regimen, not just this pair
Opens the checker with these two drugs prefilled. Add the rest of the regimen and recompute additive risks.
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Sources
- AHA/ACC: Use of Sildenafil (Viagra) in Patients With Cardiovascular Disease (2018)
- AEMPS: Ficha técnica: Nitroglicerina (nº registro 60314), sección 4.3 (2025)– AEMPS, CIMA, nº registro 60314, revisión 09/2025, sección 4.3