Which of the following is contraindicated when using nitroglycerin?

• A. SBP <90 mmHg or MAP <65, and use of PDE5 inhibitors within 24-48 hours
• B. A history of hypertension
• C. A pulse rate >100
• D. Allergy to aspirin

Answer: (A)

The key idea is that nitroglycerin safety hinges on blood pressure and potential drug interactions. Nitroglycerin dilates veins (and to some extent arteries), which lowers preload and systemic blood pressure. If the blood pressure is already very low—such as systolic under 90 mmHg or mean arterial pressure under 65 mmHg—adding nitroglycerin can cause dangerous hypotension and inadequate perfusion.

Another major risk is the interaction with phosphodiesterase-5 inhibitors (like sildenafil or similar drugs). When used within about 24–48 hours, these medications amplify nitrates’ vasodilatory effect, leading to a potentially life-threatening drop in blood pressure.

That combination is not considered safe, which is why it’s contraindicated. Other options listed aren’t automatic contraindications: a history of hypertension, a fast pulse, or an aspirin allergy do not by themselves rule out nitroglycerin use, though they may require separate assessment.