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Organic nitrate Pregnancy: Safety and efficacy during pregnancy or lactation have not been established.

Isosorbide mononitrate

Brand names: Imdur, Monomil, Ismo, Elantan

Isosorbide mononitrate is an oral long-acting nitrate used for the prophylaxis of angina pectoris and as an adjunct in chronic heart failure.

Auto-extracted from the source labelling — not yet independently clinician-verified. These values were distilled from the UK SPC (or the US label where noted) but have not had a clinician sign-off. Confirm against the current SmPC before prescribing.

Adult dose

Dose: One prolonged-release tablet (60 mg) once daily in the morning; the dose may be increased to 120 mg (two tablets) daily, both taken once daily in the morning
Route: Oral - tablets must not be chewed or crushed; swallow whole with a small amount of water
Frequency: Once daily in the morning
Max: 120 mg (two tablets) daily, taken once daily in the morning - the highest dose stated in this SPC
SOURCE SCOPE: the SPC fetched is 'Carmil XL 60 mg Tablets' (Monomil XL / Carmil XL prolonged-release tablets), so the regimen above is for the once-daily modified-release preparation. Standard (immediate-release) isosorbide mononitrate tablets follow a different, twice-daily regimen and are NOT covered by this source. Titration: the dose can be titrated to minimise the possibility of headache by initiating treatment with 30 mg for the first 2 to 4 days. The score line on the tablet is not intended to divide the tablet into equal halves. Not indicated for the relief of acute angina attacks - in the event of an acute attack, sublingual or buccal glyceryl trinitrate tablets should be used (SPC section 4.4). Paediatric: safety and efficacy in children have not been established. Elderly: no evidence of a need for routine dosage adjustment, but special care may be needed in those with increased susceptibility to hypotension or marked hepatic or renal insufficiency. The tablet core is insoluble in digestive juices and the matrix may very occasionally be visible in the stool after all active substance has been released. Contains lactose. Cross-check only (openFDA, US labelling for immediate-release isosorbide mononitrate tablets, not this UK prolonged-release SPC): recommended regimen 20 mg twice daily with the doses seven hours apart; a starting dose of 5 mg may be appropriate for persons of particularly small stature but should be increased to at least 10 mg by the second or third day; doses above 20 mg twice daily have not been adequately studied - this US figure has NOT been used for the dose field.

Dose adjustments

Renal

No routine dosage adjustment is specified, but special care may be needed in patients with marked hepatic or renal insufficiency (stated in the elderly paragraph of SPC section 4.2).

Dose auto-extracted from UK Summary of Product Characteristics (SPC) via the eMC; US FDA prescribing information (openFDA / DailyMed) — cross-check; US labelling may differ from UK — not yet clinician-verified. Always confirm against the product SmPC and your local formulary before prescribing.

Contraindications

  • Hypersensitivity to the active substance or to any of the excipients
  • Constrictive cardiomyopathy and pericarditis
  • Aortic stenosis, mitral stenosis, cardiac tamponade
  • Severe anaemia
  • Must not be given with phosphodiesterase type 5 inhibitors (e.g. sildenafil)
  • Severe cerebrovascular insufficiency or hypotension are relative contraindications

Side effects

  • Headache (common) - may occur when treatment is initiated but usually disappears after 1-2 weeks
  • Dizziness (common); fainting (rare)
  • Hypotension and tachycardia (common)
  • Nausea (common); vomiting and diarrhoea (uncommon)
  • Rash, pruritus (rare); myalgia (very rare)

Interactions

  • Phosphodiesterase type 5 inhibitors (e.g. sildenafil) - concomitant administration can potentiate the vasodilatory effect with potential for serious side effects such as syncope or myocardial infarction; must not be given concomitantly

Clinical monograph

How it works

It is converted to nitric oxide, which raises smooth-muscle cyclic GMP to produce venous and arterial dilatation, reducing cardiac preload and afterload and so lowering myocardial oxygen demand.

Prescribing in practice

  • It is contraindicated with phosphodiesterase-5 inhibitors (such as sildenafil) because the combination can cause profound, potentially life-threatening hypotension.
  • A daily nitrate-free interval is essential to prevent tolerance, so dosing should be asymmetric rather than evenly spaced around the clock.
  • Headache and postural hypotension are common, especially on initiation and dose increases.

Monitoring

Monitor for symptomatic benefit and for hypotension, with blood pressure review particularly after initiation or dose change.

Counselling the patient

  • Do not use erectile-dysfunction medicines such as sildenafil while taking nitrates.
  • Headaches are common at first and usually ease with continued treatment; tell your doctor if they persist.
  • Stand up slowly, as this medicine can make you feel dizzy or faint.

Evidence & guidelines

Long-acting nitrates are an established second-line antianginal option in NICE guidance for stable angina, used where beta-blockers or calcium-channel blockers are insufficient or unsuitable.

Reference: NICE NG185; Drug verified in RxNorm (NLM); confirm dosing against the manufacturer SPC (eMC). Verify against your local formulary and current prescribing references before prescribing. The structured dose values shown have been reviewed by a clinician. Monograph status: clinician-reviewed (2026-07-04).

Related

Curated clinical cross-links plus same-class fallbacks.

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