Sildenafil Side Effects Guide
Table of Contents
Key Takeaways
- Most common: Headache (10% of users), flushing, nasal congestion.
- Onset: Typically 30 mins–4 hours after taking.
- Duration: Mild effects last 4–12 hours; serious effects may persist longer.
- Emergency signs: Priapism (>4 hours), vision loss, or severe allergic reactions.
- Risk factors: Nitrate use, heart conditions, age >75.
Common Sildenafil Side Effects
Very Common (≥1 in 10 users)
- Headache Common
- Facial flushing Common
- Nasal congestion Common
Less Common (1 in 100–1,000 users)
- Dizziness Uncommon
- Blurred vision Uncommon
- Indigestion Uncommon
When Do Sildenafil Side Effects Start?
| Side Effect | Typical Onset | Peak Intensity |
|---|---|---|
| Headache/Flushing | 30 mins–1 hour | 1–2 hours |
| Vision changes | 1–4 hours | 4–6 hours |
| Priapism | Within 4 hours | Medical emergency |
| Allergic reaction | Immediate–30 mins | 1–2 hours |
How Long Do Side Effects Last?
| Side Effect | Duration | Management |
|---|---|---|
| Headache/Flushing | 4–12 hours | Hydration, rest |
| Vision changes | 12–24 hours | Medical review if persistent |
| Priapism | >4 hours (emergency) | Seek immediate help |
| Allergic reaction | Days (requires treatment) | Stop Sildenafil, use antihistamines |
Serious Side Effects Requiring Immediate Action
- Priapism: Erection lasting >4 hours (risk of permanent damage).
- Vision loss: Sudden decrease or blurred vision (NAION risk).
- Allergic reaction: Swelling (face/throat), difficulty breathing.
- Chest pain: Especially with nitrate use.
Risk Factors for Serious Reactions
- Heart disease: Recent heart attack/stroke.
- Nitrate use: GTN spray, isosorbide mononitrate.
- Retinitis pigmentosa: Rare eye condition.
FAQs
Why does Sildenafil cause headaches?
Headaches occur due to vasodilation (widening of blood vessels) in the brain. They typically:
- Start within 1 hour
- Last 4–12 hours
- Can be managed with paracetamol (avoid NSAIDs if on blood thinners)
Consult your doctor if severe or persistent.
Can Sildenafil cause permanent vision damage?
While rare, NAION ("eye stroke") has been reported in men with:
- Pre-existing optic nerve issues
- Heart disease or diabetes
- Age >50
Stop Sildenafil and seek immediate help if vision changes occur.
 | Authored by Nabeel |
Medical Content Manager
Nabeel is a co-founder, and medical content manager of Chemist Doctor. He works closely with our medical team to ensure the information is accurate and up-to-date.
 | Reviewed by Dr. Waqas (GMC:7928708) |
Medical Doctor
Dr. Waqas is a GMC-registered doctor at Chemist Doctor, specialising in general health. He balances clinical precision with cultural sensitivity.
 | Approved by Usman |
Medical Director
Usman is a co-founder, and medical director of Chemist Doctor. He leads the organisation's strategic vision, bridging clinical and operational priorities.
Review Date: 12 August 2025
Next Review: 14 February 2026
Published on: 11 August 2025
Last Updated: 12 August 2025
Popular Conditions
Useful Links
We Are Regulated
