What are the indications for administering nitroglycerin?

Nitroglycerin is primarily indicated for patients experiencing chest pain that is suspected to be of cardiac origin, such as angina or myocardial infarction (MI). This medication works by dilating blood vessels, which improves blood flow to the heart muscle. In the context of a cardiac event, this can help relieve pain and reduce the heart's workload by decreasing oxygen demand. The rapid onset of action makes it effective for acute management of chest pain, allowing for prompt treatment while awaiting further medical assistance.

The other options do not align with the primary uses of nitroglycerin. For instance, it's not indicated for managing severe allergic reactions, as other medications like epinephrine would be required in those cases. Similarly, while nitroglycerin can affect blood pressure, it is not specifically used for pain relief related to muscle cramps or for the treatment of hypertension unless it falls under the necessary protocol for a cardiac patient.