Sildenafil BNF: Essential Clinical Information

Sildenafil is a PDE5 inhibitor prescribed for erectile dysfunction, available as both branded Viagra and generic sildenafil. This prescription-only medicine requires clinical assessment and proper medical guidance. Understanding dosages, contraindications, and safety information is crucial for appropriate treatment. EverydayMeds offers both branded and generic options following online consultation with UK-licensed prescribers for eligible patients.

  • Available in 25mg, 50mg, and 100mg strengths with 50mg typical starting dose
  • Take 30-60 minutes before sexual activity, maximum once per 24 hours
  • Contraindicated with nitrates, severe heart disease, and certain medications
  • Requires prescription following clinical assessment by qualified prescriber
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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.

Complete Sildenafil Clinical Reference Guide

Mechanism of Action and Clinical Effects

Sildenafil functions as a phosphodiesterase type 5 (PDE5) inhibitor, selectively blocking the enzyme responsible for breaking down cyclic guanosine monophosphate (cGMP). This mechanism increases blood flow to penile tissue during sexual arousal, facilitating erectile function. The medication requires sexual stimulation to be effective and does not cause automatic erection. Clinical effects typically begin within 30-60 minutes and may persist for 4-6 hours, though this refers to the therapeutic window rather than duration of erection.

Dosage and Administration Guidelines

Sildenafil is available in three strengths: 25mg, 50mg, and 100mg tablets. The standard starting dose is 50mg, taken approximately one hour before anticipated sexual activity. Based on individual response and tolerability, the dose may be increased to 100mg or reduced to 25mg. The maximum frequency is once per 24-hour period. Food intake, particularly high-fat meals, may delay absorption and onset of action. EverydayMeds provides both branded Viagra and generic sildenafil options, allowing patients to choose based on preference and budget following clinical assessment.

Contraindications and Safety Considerations

Several absolute contraindications exist for sildenafil use. Concurrent nitrate therapy represents a dangerous interaction due to potentially fatal hypotension. Patients with severe cardiovascular disease, recent myocardial infarction or stroke (within six months), severe hepatic impairment, or hypotension should not use sildenafil. Additional contraindications include riociguat therapy, hereditary retinal disorders, and known hypersensitivity to sildenafil or excipients.

Drug Interactions and Precautions

Critical drug interactions require careful consideration. Alpha-blockers may cause symptomatic hypotension when combined with sildenafil, necessitating dose adjustment or timing modifications. CYP3A4 inhibitors such as ketoconazole, ritonavir, or erythromycin may increase sildenafil concentrations, requiring dose reduction. Patients should inform prescribers of all medications, including over-the-counter preparations and herbal supplements, during clinical assessment.

Accessing Treatment Through EverydayMeds

EverydayMeds facilitates access to both branded Viagra and generic sildenafil through comprehensive online consultation with UK-licensed prescribers. The clinical assessment evaluates medical history, current medications, cardiovascular health, and treatment suitability. Eligible patients can choose between branded and generic formulations at checkout, with discrete delivery throughout the UK. All treatments are dispensed from registered UK pharmacies following appropriate clinical oversight and safety protocols.

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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