Adult: Dosage must be individualised according to clinical response. Prophylaxis and long-term treatment: As immediate-release tab: 20 mg 2 or 3 times daily. Dose may range from 20-120 mg daily in divided doses. Prophylaxis: As extended-release/prolonged-release tab or cap: Initially, 30-60 mg once daily in the morning. Doses may be increased to 120 mg once daily if necessary. Use the lowest effective dose.
Oral Congestive heart failure
Adult: Adjunctive therapy in cases not responding to cardiac glycosides and/or diuretics: As immediate-release tab: 20 mg 2 or 3 times daily depending on individual needs and continuous haemodynamic monitoring.
Administration
Should be taken on an empty stomach.
Contraindications
Severe hypotension, hypertrophic obstructive cardiomyopathy, constrictive pericarditis, cardiac tamponade, aortic or mitral valve stenosis, acute circulatory failure/shock, circulatory collapse, cardiogenic shock, acute MI with low left ventricular filling pressure, conditions associated with increased intracranial pressure (e.g. cerebral haemorrhage, head trauma), closed-angle glaucoma, marked anaemia, hypovolaemia. Concomitant use with phosphodiesterase-5 (PDE-5) inhibitors (e.g. sildenafil) or riociguat.
Special Precautions
Patient with recent history of MI, inferior wall MI and suspected right ventricular infarctions; hypothyroidism, hypoxaemia, malnutrition, hypothermia. Not indicated for the treatment of acute angina attacks. Avoid abrupt withdrawal. Severe renal and hepatic impairment. Elderly. Pregnancy and lactation.
Adverse Reactions
Significant: Severe hypotension accompanied by paradoxical bradycardia and increased angina pectoris; orthostatic hypotension, syncope; increased intracranial pressure; drug tolerance, CNS depression, headache. Cardiac disorders: Tachycardia. Ear and labyrinth disorders: Vertigo. Gastrointestinal disorders: Nausea, vomiting, diarrhoea, gastrointestinal disturbance. General disorders and administration site conditions: Asthenia, tiredness. Nervous system disorders: Dizziness, restlessness. Psychiatric disorders: Somnolence, sleep disturbance. Skin and subcutaneous tissue disorders: Rash, pruritus, increased sweating. Respiratory, thoracic and mediastinal disorders: Transient hypoxaemia. Vascular disorders: Pallor, flushing.
This drug may cause dizziness, blurred vision, and postural hypotension; if affected, do not drive or operate machinery.
Monitoring Parameters
Monitor blood pressure and heart rate.
Overdosage
Symptoms: Hypotension, headache, dizziness, nausea, vomiting, excitation, tachycardia, sweating, syncope, vertigo, restlessness, flushing, blurred vision, confusion, increased intracranial pressure, and neurological deficits. Rarely, methaemoglobinaemia in very high doses. Management: Symptomatic treatment. Administer activated charcoal within 1 hour of ingesting toxic doses; perform gastric lavage if necessary. To treat hypotension, place the patient in a supine position with the legs raised; administer normal saline IV infusion as necessary. For severe hypotension, may administer inotropes (e.g. dopamine, dobutamine). In case of methaemoglobinaemia, give 1-2 mg/kg IV methylene blue.
Drug Interactions
Increased risk of orthostatic hypotension with Ca channel blockers. Additive hypotensive effect with other vasodilators, β-blockers, angiotensin II receptor antagonists, ACE inhibitors, aldesleukin, alprostadil, and TCAs. May increase the plasma levels and hypertensive effects of dihydroergotamine. Potentially Fatal: Severe hypotension may occur when used with PDE-5 inhibitors (e.g. sildenafil, tadalafil, vardenafil) or riociguat.
Food Interaction
Increased risk of hypotension with alcohol. May reduce the rate but not the extent of absorption with food.
Lab Interference
May cause falsely low serum cholesterol determination with Zlatkis-Zak colour reaction.
Action
Description: Isosorbide mononitrate is a vasodilator and the major active metabolite of isosorbide dinitrate. It serves as an exogenous source of nitric oxide which causes vascular smooth muscle relaxation and consequent dilation of peripheral arteries and veins. This effect decreases the left and right ventricular end-diastolic pressures and volume, thereby improving the subendocardial blood flow. Onset: Within 20-45 minutes. Duration: ≥6 hours (immediate-release); ≥12-24 hours (extended-release). Pharmacokinetics: Absorption: Readily and completely absorbed from the gastrointestinal tract. May reduce the rate but not the extent of absorption with food. Bioavailability: Approx 100%. Time to peak plasma concentration: 30-60 minutes. Distribution: Distributed into the blood cells and saliva. Volume of distribution: Approx 0.6 L/kg. Plasma protein binding: <5%. Metabolism: Metabolised in the liver into nitric oxide (active) and other inactive metabolites, such as isosorbide and isosorbide glucuronide. Excretion: Mainly via urine (2% as unchanged drug); faeces (1%). Elimination half-life: Approx 5 hours.
Chemical Structure
Isosorbide mononitrate Source: National Center for Biotechnology Information. PubChem Compound Summary for CID 27661, Isosorbide mononitrate. https://pubchem.ncbi.nlm.nih.gov/compound/Isosorbide-mononitrate. Accessed Aug. 24, 2020.
Storage
Store between 20-30°C. Protect from light and moisture.
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