Isordil (Isosorbide Dinitrate) Side Effects in Pakistan

A complete guide to the side effects of Isordil (ISDN). Headache is the most common but usually improves. The most important warning: the combination with PDE5 inhibitors is life-threatening — this awareness is essential.

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 Isordil include headache, low blood pressure, flushing, and palpitations. The most serious warning: NEVER take with PDE5 inhibitors (sildenafil/Viagra, tadalafil) — fatal hypotension can occur.

Side Effects at a Glance

Common

Headache
Hypotension / dizziness
Flushing
Reflex tachycardia
Palpitations
Nausea

Serious — See a Doctor

Severe hypotension — FATAL with PDE5 inhibitors (sildenafil/Viagra, tadalafil/Cialis) — ABSOLUTELY CONTRAINDICATED
Syncope / fainting
Methaemoglobinaemia (rare — high doses — bluish skin/lips, confusion, breathlessness)

When to See a Doctor Immediately

Severe dizziness, near-fainting, or loss of consciousness (hypotension) — see a doctor immediately
Chest pain not resolved after 3 sublingual doses (15 min) — IMMEDIATE EMERGENCY (possible heart attack)
Headache still severe after 2 weeks — dose adjustment necessary
Bluish skin or lips + confusion (methaemoglobinaemia — rare but emergency)
Rapid or irregular heartbeat (palpitations)
If sildenafil/tadalafil is also prescribed and isordil has been issued — inform your doctor IMMEDIATELY

Isordil (Isosorbide Dinitrate) Side Effects (Nuksanat)

Isordil (ISDN) is generally effective for angina management, but its side effects — particularly in the first few weeks — are quite common. The most important warning is the fatal interaction with PDE5 inhibitors.

CRITICAL WARNING — PDE5 INHIBITORS

Sildenafil (Viagra, Revatio), tadalafil (Cialis), vardenafil (Levitra), or any PDE5 inhibitor + Isordil = POTENTIALLY FATAL HYPOTENSION

This combination is ABSOLUTELY CONTRAINDICATED. If you are taking any medicine for erectile dysfunction or pulmonary hypertension, inform your doctor IMMEDIATELY before starting isordil.

Common Side Effects (Aam Nuksanat)

Headache — most common; pulsating/throbbing; more frequent in the first 1-2 weeks; usually resolves on its own; manage with paracetamol
Hypotension / dizziness — low blood pressure, dizziness; sit down after a dose
Flushing — redness of the face and skin — harmless but bothersome
Reflex tachycardia — rapid heartbeat
Palpitations — awareness of heartbeat
Nausea — mild; usually improves

Headache Management (Sar Dard Se Kaise Bachein)

Paracetamol (500mg-1g) can be taken for headache
Starting at a low dose reduces headache incidence
Usually improves within 1-2 weeks — do not stop the medicine

Serious Side Effects

Severe Hypotension (with PDE5 inhibitors — FATAL)

The combination with PDE5 inhibitors drops blood pressure to levels that can cause organ damage or death. This interaction is dose-independent — even a single tablet can be fatal in combination.

Syncope / Loss of Consciousness

Fainting can occur during a severe hypotension episode — hot weather, alcohol, or dehydration further increases the risk.

Methaemoglobinaemia (Rare)

At high doses — bluish/greyish skin and lips, confusion, breathlessness. EMERGENCY — go to hospital immediately.

When to See a Doctor

Chest pain not resolved after 3 sublingual doses — IMMEDIATE EMERGENCY (heart attack)
Severe dizziness or loss of consciousness
Headache still severe after 2 weeks
Palpitations / tachycardia
Bluish skin (methaemoglobinaemia)
PDE5 inhibitor has also been prescribed — INFORM DOCTOR IMMEDIATELY

Side Effects Summary Table

Type	Side Effect	Action
Very Common	Headache	Paracetamol; usually improves within 2 weeks
Common	Hypotension / dizziness	Sit down; rise slowly
Common	Flushing / tachycardia	Monitor; inform doctor if severe
CRITICAL	PDE5 inhibitor interaction	NEVER combine — FATAL
Rare	Methaemoglobinaemia	EMERGENCY

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

Isordil se sar dard kyun hota hai?

Nitrates cause cerebral vasodilation — this produces a pulsating headache. It is common in the first 1-2 weeks and usually improves. It can be managed with paracetamol. See a doctor for dose adjustment if the headache is severe.

Isordil lene ke baad chakkar kyon aata hai?

Nitrates dilate blood vessels — blood pressure can drop, especially on standing (postural hypotension). After the first dose, sit or lie down. Rise slowly.

Kya isordil ke saath sildenafil (Viagra) le sakte hain?

ABSOLUTELY NOT — this combination is ABSOLUTELY CONTRAINDICATED. Together they drop blood pressure to life-threatening levels. If both are prescribed, inform your doctor IMMEDIATELY — never use both at the same time.

Isordil ka sar dard kitne time mein theek hota hai?

Headache usually improves after 1-2 weeks of regular use as the body adapts to the vasodilation effects of nitrates. If still severe after 2 weeks, ask your doctor for dose adjustment.

Kya isordil se skin laal ho jaati hai?

Yes — flushing is a common side effect of the nitrate class. It occurs due to vasodilation and is generally harmless, but if accompanied by a severe drop in blood pressure, see a doctor.

Brand alternatives, same-class options, and other medicines used for the same conditions as Isordil Tablet.

Used for the same conditions

Other medicines commonly used for stomach pain (abdominal pain) and overlapping conditions.

Stomach Pain (Abdominal Pain) hub →

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.