Isosorbide Mononitrate
Imdur is the brand-name version of isosorbide mononitrate, a nitrate medicine that prevents angina by relaxing the heart’s blood vessels. It comes in four tablet strengths, from 20 mg to 60 mg.
Key points
- Prevents, does not treat. Isosorbide mononitrate stops angina attacks from starting; it will not relieve one already in progress.
- Never combine with PDE5 inhibitors. Sildenafil, tadalafil and vardenafil taken alongside this medicine can cause a severe and possibly fatal drop in blood pressure.
- Unlike nitroglycerin, isosorbide is well absorbed through the gut without being broken down by the liver first, which is why it works as a standard daily tablet.
How does isosorbide mononitrate work?
Isosorbide mononitrate releases nitric oxide in the walls of blood vessels. Nitric oxide relaxes the smooth muscle around veins, so more blood pools in the legs and less returns to the heart. The heart then pumps against a lower volume and needs less oxygen. Arteries in the heart also widen, improving blood flow to the muscle itself. Together these effects reduce the strain that triggers angina pain.