Which condition is a contraindication for administering Nitroglycerin?

• A. SBP < 90 mmHg or MAP < 65 mmHg or recent PDE-5 inhibitor use
• B. SBP > 180 mmHg
• C. No chest pain
• D. History of stable angina

Answer: (A)

Nitroglycerin is given to relieve chest pain by dilating veins and reducing preload, which lowers myocardial oxygen demand. A key safety rule is to avoid it when blood pressure is too low or when a PDE-5 inhibitor has been used recently. If systolic blood pressure is under about 90 mmHg or mean arterial pressure under about 65 mmHg, further vasodilation can cause dangerous hypotension and worsen perfusion, so nitroglycerin is contraindicated. Similarly, PDE-5 inhibitors (such as sildenafil or tadalafil) potentiate the BP-lowering effect of nitrates by increasing and preserving cGMP, which can lead to a severe, potentially life‑threatening drop in blood pressure; this combination is a clear contraindication. By contrast, having high blood pressure, no chest pain at the moment, or a history of stable angina does not in itself forbid nitroglycerin use.