Isosorbide

1 medicine

Isosorbide is a nitrate that widens blood vessels to relieve and prevent angina chest pain. It must never be combined with PDE5 inhibitors such as sildenafil or with riociguat, because together they cause a dangerous drop in blood pressure.

Imdur

Isosorbide

20/30/40/60mg

Imdur is a heart blood pressure medication containing Isosorbide, available as 20/30/40/60mg tablets.

from $0.57 / tablet View

Key facts

  • Isosorbide (isosorbide dinitrate or isosorbide mononitrate, sold as Monoket and other brands) is a nitrate. It releases nitric oxide, which relaxes and widens blood vessels.
  • It is used to prevent and relieve angina, and longer-acting forms are taken with a nitrate-free interval each day so the medicine does not lose effect.
  • Never take isosorbide with a PDE5 inhibitor (sildenafil, tadalafil, vardenafil, avanafil) or the drug riociguat. Combined, they can cause a severe, sometimes fatal, drop in blood pressure.
  • Seek urgent care for chest pain that does not ease with rest and your usual fast-acting dose, or for fainting.

What isosorbide treats

Isosorbide treats and prevents angina, chest pain or pressure that occurs when the heart muscle does not get enough oxygen-rich blood, often during exertion. A fast-acting tablet or spray placed under the tongue relieves an angina attack as it starts; longer-acting tablets are taken regularly to prevent attacks. It is sometimes added to other medicines in heart failure to ease the heart's workload. It is not a general painkiller and does not treat a heart attack once it has started.

How isosorbide works

Isosorbide is converted in the body to nitric oxide, a signal molecule that relaxes the smooth muscle in blood vessel walls. This widens veins more than arteries, reducing the amount of blood returning to the heart and lowering its workload, and it also widens the coronary arteries, improving blood flow to the heart muscle itself.

Before you take it

  • Do not use isosorbide if you take a PDE5 inhibitor or riociguat, or if you have severe anaemia, very low blood pressure, or raised pressure inside the skull.
  • Tell your prescriber about a recent heart attack, a bleeding stroke, or narrowing of the heart valves; these can make nitrates unsafe.
  • Alcohol adds to the blood-pressure-lowering effect and can cause dizziness or fainting.
  • If you take a long-acting nitrate regularly, do not stop it abruptly. Stopping suddenly after prolonged use can bring on rebound chest pain; your prescriber will advise how to reduce the dose if it needs to stop.

Side effects

Common effects include headache, flushing, light-headedness and a fast heartbeat, especially when starting treatment or increasing the dose.

Stop and seek urgent medical care for any of these:

  • Chest pain that does not ease with rest and your usual fast-acting dose.
  • Fainting or severe dizziness.
  • A very fast or irregular heartbeat.

Safety essentials

  • The nitrate rule is absolute: no isosorbide within the recommended window of any PDE5 inhibitor dose (at least 24 hours, longer for tadalafil), and no PDE5 inhibitor while isosorbide is in your system. Tell any emergency team you have taken a nitrate if chest pain occurs during sex.
  • If you use long-term nitrate tablets or patches, do not stop them suddenly; your prescriber will taper the dose to avoid rebound angina.
  • Headache is common early in treatment; do not stop the medicine on your own account, since it usually eases as your body adjusts.

This page is educational and does not replace advice from a doctor or pharmacist who knows your health history.