Isosorbide mononitrate
- Class: Nitrate
- Used for: angina
- Say it: eye-soh-SOR-bide mon-oh-NYE-trate
- Forms: tablet
ISOSORBIDE MONOnitrate = MONO, ONE dose a day, taken to PREVENT the angina — never to stop an attack.
Its long action is for background prevention. Reaching for it during chest pain is the error: that is nitroglycerin's job, under the tongue.
A long-acting nitrate for prevention, not for an attack in progress. It needs a daily nitrate-free gap, or the vessels simply stop responding to it.
Side effects
Common: headache, dizziness, flushing
Serious: severe pressure drop with sildenafil
Typical dose
30–60 mg once daily, up to 120 mg
The once-daily modified-release form builds its own nitrate-free window; immediate-release needs the doses bunched in the day.
Check yourself
Why does isosorbide mononitrate need a daily nitrate-free interval?
- Without one, tolerance develops and the drug stops working
- To protect the kidneys
- To prevent physical dependence
- To let the blood pressure recover overnight
Show answer
A. Without one, tolerance develops and the drug stops working
Uninterrupted exposure blunts the vessels' response within a few days. A nitrate-free gap restores it — which is why the dosing schedule is deliberately asymmetric.
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