Isosorbide mononitrate
Organic nitrates
Organic nitrates
The active metabolite of isosorbide dinitrate, given by mouth to prevent angina. It has no first-pass loss, so its effect is more predictable.
Quick facts
- Group
- Organic nitrates
- Target
- Soluble guanylate cyclase (activated by nitric oxide)
- Key effects
- Headache · Dizziness · Lightheadedness on standing
- Monitor
- Blood pressure
- ATC
- C01DA14
No doses: the clinician sets them by the current guideline.
Mechanism of action
Isosorbide mononitrate releases nitric oxide, which activates soluble guanylate cyclase; cGMP rises and vascular smooth muscle relaxes, mostly in veins. Lower preload and wall tension reduce the oxygen the heart needs, so exertional angina occurs less often.
- Isosorbide mononitrate releases nitric oxide
- cGMP rises and venous smooth muscle relaxes
- Less preload means less oxygen demand and fewer attacks
Indications
- Prevention of angina pectoris due to coronary artery disease Stable angina →
Adverse effects
Common
- Headache
- Dizziness
- Lightheadedness on standing
- Nausea
Contraindications
- Hypersensitivity or idiosyncratic reaction to nitrates or nitrites
- Combination with PDE5 inhibitors such as sildenafil is avoided (severe hypotension)
Key interactions
- Sildenafil and other PDE5 inhibitors
- Severe hypotension
- Calcium channel blockers
- Marked orthostatic hypotension
- Alcohol and other vasodilators
- Additive hypotension
What is monitored
- Blood pressure, lying and standing
- Angina frequency and exercise tolerance
Administration and safety
- Immediate-release and extended-release products follow different schedules: the product is checked.
- The regimen leaves a daily nitrate-free period to prevent tolerance.
- Not a rescue medicine: sublingual glyceryl trinitrate is used for acute pain.
Pregnancy and breastfeeding
Human data are limited; it is used in pregnancy only when the benefit justifies the risk.
Nursing care
- Check blood pressure and ask about dizziness on standing.
- Ask about PDE5 inhibitors before giving it.
- Teach not to stop it suddenly and to keep sublingual glyceryl trinitrate for attacks.
Pharmacokinetics
- Absorption
- Near-complete oral bioavailability with no first-pass metabolism
- Distribution
- Spreads into total body water
- Elimination
- Kinetics are similar in kidney or liver disease and heart failure
- Onset and duration
- Too slow to abort an acute attack
Test yourself
Think of the answer, then tap the question to see it.
Why is the effect of isosorbide mononitrate more predictable than that of the dinitrate?
It is not subject to first-pass metabolism, so oral bioavailability is near complete.
What prevents tolerance with once-daily extended-release isosorbide mononitrate?
The schedule leaves a period each day with low nitrate levels.
Which drug combination with isosorbide mononitrate can cause severe hypotension?
PDE5 inhibitors such as sildenafil (and other vasodilators, alcohol or calcium channel blockers to a lesser degree).
Connections
← Back to the class: Organic nitrates
Educational content on how drugs work; not a prescribing guide and no substitute for a health professional's advice. No doses are given.
Sources: DailyMed - ISOSORBIDE MONONITRATE tablet, extended release (DailyMed (U.S. National Library of Medicine), 2026); Isosorbide: MedlinePlus Drug Information (MedlinePlus (U.S. National Library of Medicine), 2026); ATCDDD - ATC/DDD Index (WHO Collaborating Centre for Drug Statistics Methodology, 2026).
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Representative model, for educational purposes only.