Final answer:
The most common side effect of nitroglycerin, a medication used to treat chest pain or angina, is a headache, but it may also cause dizziness, lightheadedness, or fainting due to lowered blood pressure.
Step-by-step explanation:
After administration of nitroglycerin to a patient with chest pain, the most common side effect you might expect to see is headache. Nitroglycerin is a medication that works by dilating blood vessels, which helps to improve blood flow to the heart muscle and relieve chest pain, also known as angina. However, as it decreases blood pressure, it may also lead to other side effects such as dizziness, lightheadedness, or fainting, particularly if the patient stands up too quickly after taking the drug - a condition called orthostatic hypotension.