What is the primary action of Ranexa (ranolazine) in treating chronic stable angina?

Ranexa (ranolazine) primarily acts by improving myocardial energy metabolism, which is especially beneficial in treating chronic stable angina. It does this by inhibiting the late sodium current in cardiac myocytes. This action helps to reduce intracellular sodium levels and minimizes calcium overload, which can lead to increased myocardial oxygen demand and ischemia.

In the context of the choices provided, while it is often thought that ranolazine could act as a substitute for beta blockers due to its effects on the heart, it is not a direct replacement but rather serves as an alternative or adjunctive therapy for patients who cannot tolerate beta-blockers or for those that still experience angina despite optimal beta-blocker therapy. Ranolazine does not typically lower blood pressure, reduce heart rate significantly, or directly prevent myocardial infarction, which makes it a distinctive option that typically complements other antianginal therapies rather than substituting them outright.