Isosorbida

Isosorbida, or isosorbide, refers to a group of organic nitrates derived from sorbitol. The two main pharmaceutical forms are isosorbide dinitrate (ISDN) and isosorbide mononitrate (ISMN). Both act as vasodilators and are used primarily in the prevention of angina pectoris and as components of certain heart failure regimens.

Mechanism of action is widespread: these compounds release nitric oxide (NO) in vascular smooth muscle, activating guanylate cyclase and increasing cyclic GMP. This causes relaxation of smooth muscle, with a predominant effect on venous capacitance vessels and a modest arterial dilation. The result is reduced preload and, to a lesser extent, afterload, improved coronary perfusion, and lower myocardial oxygen demand.

Clinical uses and administration vary. ISDN and ISMN are used for long-term prophylaxis of angina in patients with coronary artery disease. They are available in oral, sublingual, and transdermal formats, with ISMN offering relatively consistent oral bioavailability compared with ISDN, which undergoes significant first-pass metabolism. Their routes and dosing schemes are chosen to balance anti-anginal efficacy with tolerance considerations.

Tolerance can develop with continuous exposure, so regimens typically include nitrate-free intervals to preserve effectiveness. Common adverse effects include headache, dizziness, flushing, and orthostatic hypotension. Important drug interactions include concurrent use with phosphodiesterase-5 inhibitors, which can cause dangerous hypotension. Nitrates are contraindicated in cases of severe hypotension, hypovolemia, or known hypersensitivity.