[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [Pharmacology](https://durgical.com/en/pharmacology/) › [Organic nitrates](https://durgical.com/en/pharmacology/classes/organic-nitrates/) › Isosorbide mononitrate

# 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.

Updated Nov 1, 2026

## Quick facts

**Group**
[Organic nitrates](https://durgical.com/en/pharmacology/classes/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.

On this page

- The basics Mechanism of action
- Indications
- Adverse effects
- Pharmacokinetics
- Memory aid

- Safety Contraindications
- Key interactions
- What is monitored
- Administration and safety
- Pregnancy and breastfeeding
- Nursing care

- Study Test yourself

- Connections Connections

## 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 →](https://durgical.com/en/conditions/stable-angina/)

## Adverse effects

### Common

- Headache
- Dizziness
- Lightheadedness on standing
- Nausea

### Serious (rare, important)

- Severe hypotension, especially with PDE5 inhibitors
- Methaemoglobinaemia (rare)
- Rebound angina if stopped abruptly

## 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

## Memory aid

Mono means one step done: it is already the active metabolite, so no first pass and steady levels.

## 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).

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[More Pharmacology questions →](https://durgical.com/en/practice/?f=pharmacology)

## Connections

## Related drugs 2

- [Isosorbide dinitrate](https://durgical.com/en/pharmacology/isosorbide-dinitrate/)
- [Glyceryl trinitrate](https://durgical.com/en/pharmacology/glyceryl-trinitrate/)

## Related conditions 1

- [Stable angina](https://durgical.com/en/conditions/stable-angina/)

[← Back to the class: Organic nitrates](https://durgical.com/en/pharmacology/classes/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](https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=6a582db5-eb45-4320-98c1-55517d7d8c38) (DailyMed (U.S. National Library of Medicine), 2026); [Isosorbide: MedlinePlus Drug Information](https://medlineplus.gov/druginfo/meds/a682348.html) (MedlinePlus (U.S. National Library of Medicine), 2026); [ATCDDD - ATC/DDD Index](https://atcddd.fhi.no/atc_ddd_index/?code=C01DA14) (WHO Collaborating Centre for Drug Statistics Methodology, 2026).

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Representative model, for educational purposes only.

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Source: https://durgical.com/en/pharmacology/isosorbide-mononitrate/
License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/pharmacology/isosorbide-mononitrate/