Contraindications for the administration of nitroglycerin include a patient:

A. Who is 22 years of age.
B. Who recently took Viagra.
C. Who is suffering from hypertension.
D. Who has already taken one dose without relief.

Answer: B. Who recently took Viagra.
Nitroglycerin should not be given if the patient's baseline systolic blood pressure is below 90 mmHg or the systolic blood pressure has decreased more than 30 mmHg from the baseline. It should also be avoided if the heart rate is less than 50 bpm or greater than 100 bpm, if the patient has a suspected head injury, if the patient is an infant or a child, or if the patient has already taken three doses. Additionally, if the patient has taken tadalafil (Cialis), vardenafil (Levitra), or sildenafil (Viagra) within the past 24 hours, administration of nitroglycerin is contraindicated, as it may create a precipitous drop in blood pressure.