What is the first-line treatment for stable angina?

Sublingual nitroglycerin is the first-line treatment for stable angina because it is a fast-acting nitrate that provides immediate relief from angina symptoms, which occur due to transient myocardial ischemia. Nitroglycerin works by causing vasodilation of coronary vessels, increasing blood flow to the heart muscle and reducing the heart's oxygen demand by decreasing preload and afterload.

In stable angina, patients often experience predictable episodes of chest pain and discomfort related to exertion or stress. When they use sublingual nitroglycerin at the onset of symptoms, it effectively alleviates the pain within minutes, allowing them to resume activities.

Other agents mentioned, such as phenytoin, valproate, and hydroxyurea, are not appropriate for treating stable angina. Phenytoin and valproate are anticonvulsants and are not indicated for angina management. Hydroxyurea is primarily used in the treatment of sickle cell disease and certain cancers. Thus, sublingual nitroglycerin stands out as the most effective and commonly used first-line therapeutic option for quick relief from stable angina symptoms.