Final answer:
One contraindication to nitrate use in a patient with ongoing chest discomfort and possible STEMI is the use of phosphodiesterase inhibitors within the previous 24 hours.
Step-by-step explanation:
In the case of acute MI, administering nitroglycerine is a common treatment option. However, there are contraindications for its use. One of the contraindications to nitrate use in a patient with ongoing chest discomfort and possible STEMI is the use of phosphodiesterase inhibitors within the previous 24 hours. Phosphodiesterase inhibitors, such as sildenafil (Viagra), can interact with nitrate medications and cause a dangerous drop in blood pressure.