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Isosorbide Mononitrate Dosage Guide in Pakistan

The correct dosing of Isosorbide Mononitrate (ISMN) is critical for preventing nitrate tolerance. This guide covers the correct use of the SR tablet, the reason for morning dosing, and missed dose guidance.

Compiled by the PakVita Editorial Team · AI-assisted drafting with editorial review · Sourced from DRAP, WHO, BNF · Last updated:

Dosage Guide

Quick Answer

Isosorbide Mononitrate SR tablet is taken once daily in the morning as prescribed by your doctor. SR tablets must be swallowed whole — do not crush or chew. Taking in the morning provides a natural overnight nitrate-free interval which prevents tolerance. Never combine with sildenafil or tadalafil.

Dose at a Glance

Adult Dose

As prescribed — once daily SR in morning

Once daily (SR formulation)

Max: Do not exceed the recommended limit — confirm with your doctor

Child Dose (Typically adult use only)

Not typically indicated for children

Consult doctor if prescribed for child

Missed Dose

If you miss a dose, take it as soon as you remember. If the next dose is close, skip the missed dose. Never take a double dose. If forgotten at night — skip it and take the regular dose in the morning.

Overdose

An excessive dose can cause severe hypotension, throbbing headache, and fainting. Contact your doctor or emergency room immediately. NEVER take with sildenafil or tadalafil.

Isosorbide Mononitrate Dosage (Kitni leni hai)

The correct dosing of Isosorbide Mononitrate SR Tablet is essential for preventing nitrate tolerance. Always follow the doctor's prescription.

Adult Dose (Baalgon ke liye)

  • As prescribed — typically once daily SR tablet in morning
  • Do not exceed the recommended limit
  • If you forget a dose, take it as soon as you remember. If you remember at night, skip it. Never take a double dose.

Starting Dose: As prescribed (typically 20-40mg SR once daily)

Usual Dose: As prescribed — dose strength is determined by the doctor

Max Daily Dose: As prescribed — an overdose can cause severe hypotension

SR Tablet — Critical Instruction

Breaking, chewing, or crushing the SR (Sustained Release) tablet is ABSOLUTELY FORBIDDEN. Swallow the whole tablet with water. If the tablet breaks, the entire dose is released at once — risk of severe hypotension.

Why Morning Dose? (Subah kyun lena hai)

There is a specific scientific reason for taking Isosorbide Mononitrate in the morning:

1. Take the SR tablet in the morning → angina prevention throughout the day 2. Nitrate-free interval overnight (10–12 hours) — naturally achieved 3. Tolerance does not develop

If taken at night or in the evening — nitrate remains active through the night — tolerance can develop — the medicine's effectiveness diminishes.

How to Take (Kaise leni hai)

  • Take after waking in the morning
  • Swallow whole with water
  • Can be taken with or without food
  • After the first dose, sit or lie down — to avoid hypotension

Missed Dose (Dose chhoot jaye to kya karein)

  • If remembered during the day: Take it
  • If remembered at night: Skip it — take the regular dose in the morning
  • Never take a double dose

Overdose (Zyada Dose)

Severe headache, extreme dizziness, fainting, severe hypotension. Contact your doctor or emergency room immediately. Never take sildenafil or tadalafil together with this medicine — FATAL combination.

Dose Summary Table

PatientDoseNotes
Adult (angina prophylaxis)As prescribed — once daily SR, morningSwallow the SR tablet whole
ChildTypically not indicatedConsult the doctor

The information in this guide is for educational purposes only. Always confirm the dose with your doctor or pharmacist.

Frequently Asked Questions

Isosorbide Mononitrate SR ki standard dose kya hai?

The SR (sustained release) formulation is typically taken once daily in the morning — confirm the exact dose with your doctor. Swallow the SR tablet whole — do not break or chew.

Agar dose miss ho jaye to kya karein?

Take it as soon as you remember — but if you remember at night, skip it (taking it at night destroys the overnight nitrate-free interval — tolerance can develop). Resume the regular dose in the morning.

Kya SR tablet torna ya pisna sahi hai?

ABSOLUTELY NOT — breaking, chewing, or crushing the SR tablet is strictly forbidden. Doing so destroys the sustained release mechanism and the entire dose can be released at once — risk of severe hypotension.

Subah lene ki wajah kya hai?

Taking the SR formulation in the morning provides a natural overnight nitrate-free interval (10–12 hours). This interval prevents nitrate tolerance — if taken continuously for 24 hours, the medicine's effectiveness diminishes.

Kitne din tak Isosorbide Mononitrate lena chahiye?

It is a long-term daily medication — for angina management. Do not stop on your own — adjust only on the doctor's advice. Sudden discontinuation can cause rebound angina.

Sources

  1. DRAP Registered Products Database — Drug Regulatory Authority of Pakistan
  2. WHO Model List of Essential Medicines, 23rd ed. (2023) — World Health Organization
  3. British National Formulary (BNF) — BMJ Group & Pharmaceutical Press

Medical disclaimer

This page is for educational use only and does not replace professional medical advice. Always confirm diagnosis, dose, and interactions with a qualified doctor or pharmacist before starting or changing any medicine.