Sildenafil BNF Information for ED Treatment

Sildenafil, listed in the British National Formulary (BNF), is an effective prescription treatment for erectile dysfunction. As a PDE5 inhibitor, sildenafil helps increase blood flow to the penis during sexual arousal. Available as both generic sildenafil and branded Viagra, this medication requires a prescription following clinical assessment. Understanding BNF guidance helps patients make informed decisions about their ED treatment options.

  • Requires prescription following clinical assessment with UK-licensed prescriber
  • Available in 25mg, 50mg, and 100mg strengths with typical starting dose of 50mg
  • Works within 30-60 minutes and effects may last 4-6 hours
  • Choice between generic sildenafil and branded Viagra at checkout
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Not sure which one? Here's the honest comparison.

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

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.

Understanding Sildenafil: BNF Classification and Usage

What is Sildenafil According to BNF Guidelines?

The British National Formulary (BNF) classifies sildenafil as a phosphodiesterase type 5 (PDE5) inhibitor used for treating erectile dysfunction in adult men. Originally developed by Pfizer as Viagra, sildenafil is now available as both the branded version and generic alternatives. The BNF provides comprehensive guidance on prescribing, dosing, contraindications, and monitoring requirements for healthcare professionals.

How Sildenafil Works

Sildenafil works by blocking the PDE5 enzyme, which increases blood flow to the penis during sexual arousal. It's important to understand that sildenafil does not cause automatic erections - sexual stimulation is still required for the medication to be effective. The enhanced blood flow helps men achieve and maintain erections suitable for sexual activity.

BNF Dosage Recommendations

According to BNF guidance, sildenafil is available in three strengths: 25mg, 50mg, and 100mg tablets. The typical starting dose is 50mg, taken approximately 30-60 minutes before sexual activity. Based on effectiveness and tolerability, the dose may be adjusted to 25mg or increased to 100mg. The maximum recommended frequency is one dose per 24-hour period.

Contraindications and Precautions

The BNF lists several important contraindications for sildenafil use. Men taking nitrate medications (such as GTN spray or isosorbide tablets) should not use sildenafil due to potentially dangerous blood pressure drops. Other contraindications include severe cardiovascular disease, recent heart attack or stroke within six months, severe liver impairment, and very low blood pressure.

Drug Interactions

Healthcare professionals must carefully review potential drug interactions before prescribing sildenafil. The most serious interaction occurs with nitrates and nitric oxide donors, which can cause life-threatening hypotension. Other important interactions include alpha-blockers, some antifungal medications, and certain HIV protease inhibitors. The BNF provides detailed guidance on managing these interactions.

Clinical Assessment Requirements

Before prescribing sildenafil, healthcare providers must conduct a thorough clinical assessment. This includes evaluating cardiovascular health, reviewing current medications, assessing the severity of erectile dysfunction, and discussing lifestyle factors that may contribute to the condition. The assessment ensures sildenafil is both safe and appropriate for each individual patient.

Generic vs Branded Options

Patients can choose between generic sildenafil and branded Viagra, both containing the same active ingredient. Generic versions typically cost less while providing equivalent effectiveness. EverydayMeds offers both options, allowing patients to select their preferred choice during the checkout process following successful clinical assessment.

Side Effects and Monitoring

Common side effects listed in the BNF include headache, facial flushing, indigestion, and nasal congestion. Most side effects are mild to moderate and temporary. Serious side effects, though rare, include prolonged erections lasting more than four hours (priapism) and sudden vision or hearing changes. Patients should seek immediate medical attention if these occur.

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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