Which of the following is a contraindication to nitroglycerin administration?

• A. Systolic blood pressure less than 120 mm Hg
• B. History of aspirin allergy
• C. Recent head injury
• D. Renal failure

Answer: (A)

The main idea is that nitroglycerin lowers blood pressure by dilating veins and reducing preload. Giving it when systolic pressure is already low can tip the patient into dangerous hypotension, reducing coronary and cerebral perfusion. That’s why a low systolic blood pressure is a contraindication to nitroglycerin administration.

The other options don’t inherently prevent nitroglycerin use. An aspirin allergy doesn’t affect nitroglycerin’s action, so it isn’t a contraindication. Renal failure doesn’t by itself rule out nitroglycerin, and recent head injury isn’t an absolute ban in all protocols (though nitroglycerin should be used with caution in that scenario because of the risk of further lowering blood pressure and compromising perfusion).