BNF Sildenafil: When to Seek Medical Help

Understanding when sildenafil (generic Viagra) requires immediate medical attention is crucial for safe treatment. This quick reference guide covers emergency situations, when to contact your GP, and important safety information from the British National Formulary. EverydayMeds offers both branded Viagra and generic sildenafil options, ensuring you have the right treatment with proper medical guidance for erectile dysfunction management.

  • Erection lasting over 4 hours requires immediate A&E attention
  • Chest pain or breathing difficulties need urgent medical help
  • Sudden vision or hearing loss warrants immediate GP contact
  • Severe allergic reactions require emergency treatment
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Not sure which one? Here's the honest comparison.

Sildenafil
~60 min
~4 hrs
you like to plan ahead
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Tadalafil (as-needed)Most prescribed
~30 min
up to 36 hrs
you want a whole weekend covered
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Tadalafil Daily
always active
continuous
you never want to think about timing
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Vardenafil
~15–30 min
~8 hrs
you want the fastest onset
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How ED treatment works in your body.

Increases blood flow

Increases blood flow

When PDE5 is suppressed, blood is able to flow more freely through the body—including to the (you guessed it) penis.

Increase erections

Increase erections

More blood flow to the penis means harder, more satisfying erections once you're sexually stimulated.

Emergency Situations and When to Seek Help

Immediate Emergency (Call 999 or A&E)

Certain situations with sildenafil require immediate emergency medical attention. Priapism, an erection lasting more than 4 hours, is a medical emergency that can cause permanent damage if not treated promptly. Similarly, severe chest pain, difficulty breathing, or signs of heart attack whilst taking sildenafil necessitate immediate emergency care. The BNF emphasises that nitrate medications should never be given to patients who have taken sildenafil within 24 hours due to dangerous blood pressure drops.

Urgent GP Contact Required

Several symptoms warrant contacting your GP immediately or calling NHS 111. Sudden vision loss or changes, particularly in one eye, may indicate non-arteritic anterior ischaemic optic neuropathy (NAION). Sudden hearing loss or ringing in the ears also requires prompt medical assessment. Severe allergic reactions including facial swelling, difficulty swallowing, or widespread rash need urgent attention. EverydayMeds patients can access clinical support through our UK-licensed prescribers for medication-related concerns.

Routine Medical Review

Regular monitoring helps ensure sildenafil remains appropriate for your health status. Contact your prescriber if you experience persistent side effects like headaches, flushing, or indigestion that don't improve. Changes in your medical conditions, new medications, or cardiovascular symptoms require medication review. The BNF recommends periodic assessment of treatment effectiveness and tolerability. EverydayMeds offers both Viagra (branded) and sildenafil (generic) options, with clinical reviews available to optimise your treatment.

Pre-existing Conditions Requiring Caution

Certain medical conditions require careful monitoring when using sildenafil. Cardiovascular disease, including recent heart attack or stroke, may contraindicate sildenafil use. Liver or kidney impairment may require dose adjustments as outlined in the BNF. Men with anatomical penile abnormalities, blood disorders like sickle cell anaemia, or retinal problems need specialist oversight. Always inform healthcare providers about all medications and health conditions before starting sildenafil treatment.

What you need to know about erectile dysfunction

It's one of the most common conditions we treat, and one of the most treatable.

What is Erectile Dysfunction?
ED means finding it hard to get or keep an erection firm enough for sex. It's not unusual to have an off night; the point at which it's worth doing something is when it's happening regularly, or when it's starting to bother you.
How will I feel when I take ED medication?
For most men, nothing feels different day to day. The medication works in the background — when you're sexually aroused, it helps blood flow where it's needed, so erections come more easily and last longer. It doesn't cause arousal on its own. Some men notice mild, short-lived effects like a headache, facial flushing or a stuffy nose, which usually pass as the dose wears off.
Why do I need a prescription for ED medication?
ED treatments are prescription-only medicines in the UK because they aren't suitable for everyone — for example, alongside certain heart conditions or medications like nitrates. That's why we ask you to complete a short online consultation first. A UK-registered prescriber reviews your answers to make sure your chosen treatment is safe and right for you before it's dispensed.
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