How BNF Sildenafil Works for Erectile Dysfunction

Sildenafil, listed in the British National Formulary (BNF), is a clinically proven treatment for erectile dysfunction that works by increasing blood flow to the penis. Understanding how this PDE5 inhibitor functions can help patients make informed decisions about their treatment. EverydayMeds offers both branded Viagra and generic sildenafil options, allowing patients to choose their preferred treatment following a clinical consultation with our UK-licensed prescribers.

  • Blocks PDE5 enzyme to improve blood flow during sexual arousal
  • Requires sexual stimulation to work effectively
  • Takes 30-60 minutes to become active in the body
  • Effects may last 4-6 hours but don't cause prolonged erections
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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.

The Science Behind BNF Sildenafil Treatment

How Sildenafil Works in the Body

Sildenafil, as detailed in the BNF (British National Formulary), belongs to a class of medications called PDE5 inhibitors. When a man becomes sexually aroused, nitric oxide is released in the penis, which increases levels of cyclic GMP. This chemical causes the smooth muscles in blood vessels to relax, allowing increased blood flow to the penis. The enzyme PDE5 normally breaks down cyclic GMP, but sildenafil blocks this process, helping to maintain the improved blood flow needed for an erection.

Clinical Mechanism and Onset

The BNF indicates that sildenafil typically becomes effective within 30-60 minutes of taking the tablet. The medication requires sexual stimulation to work - it doesn't cause automatic erections. Food, particularly fatty meals, may delay the onset of action. The effects can last for 4-6 hours, providing a window of opportunity for sexual activity, though this doesn't mean an erection will last this entire duration.

Dosage and Administration According to BNF Guidelines

The BNF recommends starting with a 50mg dose of sildenafil, taken approximately one hour before sexual activity. Depending on effectiveness and tolerability, this may be adjusted to 25mg or increased to a maximum of 100mg. Only one dose should be taken within any 24-hour period. EverydayMeds provides both branded Viagra and generic sildenafil in all BNF-approved strengths (25mg, 50mg, 100mg).

Who May Benefit from BNF Sildenafil

According to BNF guidance, sildenafil is suitable for adult men experiencing erectile dysfunction when prescribed following appropriate clinical assessment. Our UK-licensed prescribers evaluate cardiovascular health, current medications, and medical history to ensure safe prescribing. Patients can choose between branded Viagra or cost-effective generic sildenafil during checkout, as both contain the same active ingredient.

Important Safety Considerations

The BNF highlights several contraindications for sildenafil use. It must not be taken with nitrate medications (such as GTN spray) due to dangerous blood pressure interactions. Men with severe heart conditions, recent strokes, or significant liver problems may not be suitable candidates. Our clinical assessment process ensures these safety factors are carefully evaluated before prescribing either branded or generic options.

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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