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Isosorbide Mononitrate (Imdur / Elantan) Side Effects in Pakistan

A complete guide to Isosorbide Mononitrate side effects — from common vasodilation effects to the critical PDE5 inhibitor interaction warning. Headache usually improves — if sildenafil or tadalafil is being used together, IMMEDIATE medical attention is required.

Compiled by the PakVita Editorial Team · AI-assisted drafting with editorial review · Sourced from DRAP, WHO, BNF · Last updated: 2026-06-17

Side Effects

Quick Answer

Common side effects of Isosorbide Mononitrate include headache (very common due to vasodilation — usually improves after 1-2 weeks), dizziness, flushing, and nausea. The most serious interaction is with PDE5 inhibitors (sildenafil, tadalafil) which can cause FATAL hypotension — this combination is absolutely contraindicated. Persist with headache — it usually settles with continued use.

Side Effects at a Glance

Common

Headache
Hypotension / dizziness on standing (orthostatic hypotension)
Flushing
Reflex tachycardia
Nausea
Palpitations

Serious — See a Doctor

Severe hypotension — especially with PDE5 inhibitors (sildenafil/tadalafil) — POTENTIALLY FATAL
Syncope / fainting
Methaemoglobinaemia (rare — high dose)

When to See a Doctor Immediately

If sildenafil, tadalafil, vardenafil, or avanafil was accidentally taken together — IMMEDIATE EMERGENCY
Severe dizziness or fainting
Chest pain worsening despite treatment — may indicate unstable angina
Severe headache not better after 2 weeks — discuss with doctor
Rapid or irregular heartbeat that is disturbing

Isosorbide Mononitrate (Imdur / Elantan) Side Effects (Nuksanat)

Isosorbide Mononitrate is generally well-tolerated when used at the correct dose and with a nitrate-free interval. Headache is common but usually improves. The sildenafil/tadalafil combination must be STRICTLY avoided.

Common Side Effects (Aam Nuksanat)

Headache
Hypotension / dizziness on standing (orthostatic)
Flushing
Reflex tachycardia
Nausea

Regarding headache — persevere: it usually improves within 1-2 weeks. Do not stop the medicine on your own. If unbearable, see a doctor.

Serious Side Effects (Sanjeedah Nuksanat)

Severe hypotension with PDE5 inhibitors (sildenafil, tadalafil) — POTENTIALLY FATAL — EMERGENCY
Syncope / fainting — see a doctor immediately
Methaemoglobinaemia (rare, high dose) — EMERGENCY

CRITICAL INTERACTION WARNING

> Sildenafil (Viagra), tadalafil (Cialis), vardenafil, avanafil must NEVER be taken with Isosorbide Mononitrate. Both medicines lower blood pressure — the combination can cause BP to drop so severely that the patient can collapse or die. This combination is ABSOLUTELY CONTRAINDICATED. If a patient has taken both — IMMEDIATELY go to the emergency room.

When to See a Doctor (Kab Doctor Se Milna Zaroori Hai)

PDE5 inhibitor accidentally taken together — IMMEDIATE EMERGENCY
Severe dizziness or fainting
Chest pain worsening
Severe headache not better after 2 weeks
Rapid / irregular heartbeat

Warnings and Precautions (Ihtiyat)

Don't combine with PDE5 inhibitors — FATAL
Avoid alcohol — additive hypotension
Exercise caution when driving — especially with the first dose
SR tablets must not be broken or crushed

Side Effects Summary Table

Type	Side Effect	Action
Common	Headache	Persevere — usually improves within 1-2 weeks
Common	Dizziness / BP low	Rise slowly from sitting/lying
Common	Flushing	Monitor — normal side effect
Serious	Severe hypotension (PDE5 combo)	IMMEDIATE EMERGENCY
Serious	Fainting	See a doctor

Reporting Side Effects

If you notice any unexpected side effect, report it on the DRAP pharmacovigilance portal: https://www.dra.gov.pk/pharmacovigilance

The information in this guide is for educational purposes only. If you notice any side effect, contact your doctor or pharmacist.

Frequently Asked Questions

Isosorbide Mononitrate se sar dard kyun hota hai?

Headache is the most common side effect of nitrates — vasodilation causes blood vessels in the brain to dilate which causes the headache. It usually improves after 1-2 weeks when the body adjusts. Persevere — do not stop the medicine.

Kya headache improve hoti hai Isosorbide Mononitrate se?

Yes — in most patients, headache significantly improves or resolves after 1-2 weeks of regular use. If still severe after 2 weeks, see a doctor.

Kya Isosorbide Mononitrate sildenafil ke sath le sakte hain?

ABSOLUTELY NOT — this is ABSOLUTELY CONTRAINDICATED. Both are vasodilators — combining them can cause blood pressure to drop to an extreme level (severe hypotension) which can be FATAL. If accidentally taken together, go to the emergency room IMMEDIATELY.

Kya Isosorbide Mononitrate se fainting ho sakti hai?

Yes — orthostatic hypotension can cause dizziness or fainting. After the first dose, remain sitting or lying down. Monitor blood pressure.

Kya Isosorbide Mononitrate liver ya kidney ko affect karta hai?

Significant hepatic or renal toxicity is uncommon at normal doses. It is metabolised in the liver. In liver disease, always consult a doctor. There is no significant direct effect on the kidneys.

Sources

DRAP Registered Products Database — Drug Regulatory Authority of Pakistan
WHO Model List of Essential Medicines, 23rd ed. (2023) — World Health Organization
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.