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Can I take 20 and Isosorbide mononitrate together?

Drug interaction guide

Taking sildenafil (Viagra) and isosorbide mononitrate together can cause a sudden and life-threatening drop in blood pressure. This can lead to fainting, dizziness, a heart attack, or a stroke.

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Why this happens

Both medicines work by widening your blood vessels. Isosorbide mononitrate increases a chemical called cyclic GMP to relax the vessels, and sildenafil prevents this chemical from being broken down. When used together, they cause the blood vessels to relax too much, causing blood pressure to crash.

You must NOT take sildenafil if you are using isosorbide mononitrate. This combination is strictly forbidden. If you have already taken both, seek emergency medical help immediately. Talk to your doctor about alternative treatments for erectile dysfunction that do not interfere with your heart medication.

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Taking multiple medicines? Our Medicines Interaction Checker helps you check whether your prescriptions, over-the-counter medicines, and supplements are safe to take together. Simply search for your medicines to see potential interactions and what to do about them.

Disclaimer

This information is for general educational purposes only and should not be relied upon as a substitute for professional medical advice. Always consult your GP, pharmacist, or another qualified healthcare professional before making decisions about your medications. Individual circumstances may vary, and only a healthcare professional who knows your medical history can provide personalised guidance.

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Article history

The information on this page is written and peer reviewed by qualified clinicians.

  • 14 Mar 2026 | Originally published
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