A contraindication of nitroglycerin is

• A. High blood pressure
• B. Low blood pressure
• C. Dehydration
• D. Tachycardia

Answer: (B)

Nitroglycerin works by dilating blood vessels, which lowers preload and afterload. In someone with low blood pressure, this further reduction can cause insufficient blood flow to vital organs, dizziness, fainting, or shock, so low blood pressure is a contraindication. High blood pressure isn’t a contraindication because nitroglycerin can still be used to relieve chest pain in some patients with hypertension, though it requires careful monitoring. Dehydration isn’t an outright contraindication, though it can contribute to low blood pressure. Tachycardia by itself isn’t a contraindication, although nitroglycerin can cause some reflex tachycardia. The key safety concern is the current low blood pressure, which is why that option is the correct choice.