Isosorbide dinitrate
- Class: Nitrate
- Used for: angina
- Say it: eye-soh-SOR-bide dye-NYE-trate
- Forms: tablet, sublingual tablet
ISOSORBIDE DInitrate is dosed through the DAY — and that is exactly why it stops working by the end of the week.
Continuous nitrate exposure causes tolerance within about a day. The fix is not a bigger dose but a nitrate-free gap of 8 to 12 hours, usually overnight.
Nitrates become nitric oxide and dilate veins most of all. Less blood returning means less work for the heart and less oxygen demand — that, not opening the coronary artery, is how most of the relief comes.
Side effects
Common: headache, dizziness, flushing
Serious: severe pressure drop with sildenafil
Typical dose
10–40 mg two or three times daily
Dose it asymmetrically — for example 8 am, noon and 4 pm — so the night is nitrate-free.
Check yourself
Why is a patient on regular nitrates given a nitrate-free interval each night?
- Continuous exposure causes tolerance within about a day
- Nitrates accumulate and cause kidney damage
- The drug only works while the patient is asleep
- It allows potassium to recover overnight
Show answer
A. Continuous exposure causes tolerance within about a day
Nitrate tolerance appears fast and defeats the drug entirely. A gap of 8-12 hours restores responsiveness — which is why dosing is asymmetric rather than evenly spread around the clock.
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