What is the most important mechanism of action of isosorbide mononitrate used for treating angina pectoris?

Isosorbide mononitrate primarily exerts its effects through increased cyclic guanosine monophosphate (cGMP) production. This drug belongs to a class of medications known as nitrates, which are effective in the treatment of angina pectoris due to their ability to induce vasodilation.

When isosorbide mononitrate is administered, it is converted in the body to nitric oxide (NO), a potent vasodilator. The release of nitric oxide leads to the activation of guanylate cyclase, an enzyme that catalyzes the conversion of guanosine triphosphate (GTP) into cGMP. Increased levels of cGMP in smooth muscle cells induce relaxation, resulting in vascular smooth muscle dilation. This effect primarily decreases the myocardial oxygen demand by reducing both preload and afterload, which alleviates the symptoms of angina.

The significance of the cGMP pathway is crucial in understanding how nitrates like isosorbide mononitrate provide relief from chest pain induced by ischemic heart disease. By promoting vasodilation and improving blood flow to the heart, cGMP acts as the essential mechanism through which isosorbide mononitrate functions in treating angina.