What Is Viagra & How Does It Work? | Cured Pharmacy

Clinically Proven UK Registered Pharmacy

What Is Viagra and How Does It Work?

UK-registered clinical team
Confidential and secure
No GP visit needed
Fast and discreet delivery
Start Your Free Consultation

Takes less than 2 minutes to complete 100% online

Ednew 20% off for new customers
Genuine Products
UK-licensed only
Fast Delivery
Next-day available
Expert Advice
UK pharmacists
Man using Cured Pharmacy online consultation for erectile dysfunction treatment
From £0.45 Starting dose — clinically approved
LIVE PRICING

Our Pricing

Pricing Disclaimer: Prices on some pages may not be up to date — the live pricing table below and pricing shown during consultation are official current prices and take precedence over any other figures on the site.

Sildenafil - UK-licensed prescription Treatment
Treatment

Sildenafil

From £0.45

Future orders save 5%
Start Assessment
Tadalafil - UK-licensed prescription Treatment
Treatment

Tadalafil

From £9.99

Future orders save 5%
Start Assessment
Sildenafil Eropid - UK-licensed prescription Treatment
Treatment

Sildenafil Eropid

From £8.99

Future orders save 5%
Start Assessment
Tadalafil (Teva) - UK-licensed prescription Treatment
Treatment

Tadalafil (Teva)

From £9.99

Future orders save 5%
Start Assessment
Avarante Tablets Tadalafil Tablets 10mg - UK-licensed prescription Treatment
Treatment

Avarante Tablets Tadalafil Tablets 10mg

From £11.49

Future orders save 5%
Start Assessment
Viagra Connect 50mg - UK-licensed prescription Treatment
Treatment

Viagra Connect 50mg

From £11.49

Future orders save 5%
Start Assessment

What Is Viagra and How Does It Work?

Understanding what is viagra and how does it work is essential for men considering treatment for erectile dysfunction. Viagra contains sildenafil citrate, a PDE5 inhibitor that enhances blood flow to the penis, helping achieve and maintain erections when sexually stimulated. At Cured Pharmacy, our UK-registered clinical team provides expert guidance and genuine UK-licensed treatments from £0.45, with transparent pricing and discreet delivery.

What Is Viagra and How Does It Work?

Viagra is the brand name for sildenafil citrate, the first oral treatment for erectile dysfunction licensed by the MHRA in 1998 [1]. It belongs to a class of medications called phosphodiesterase type 5 (PDE5) inhibitors, which work by blocking the enzyme that regulates blood flow in the penis.

When a man is sexually aroused, nitric oxide is released in the penile tissue, triggering a cascade that produces cyclic guanosine monophosphate (cGMP). This chemical relaxes smooth muscle cells in blood vessels, allowing increased blood flow to the corpus cavernosum — the erectile tissue of the penis [2]. PDE5 normally breaks down cGMP, limiting the duration of erections. By inhibiting PDE5, sildenafil allows cGMP to accumulate, enhancing and prolonging the erectile response.

It's crucial to understand that Viagra does not cause automatic erections. Sexual stimulation is required to initiate the nitric oxide release that starts the process [1]. The medication simply amplifies the body's natural erectile mechanism when arousal occurs.

How Effective Is Viagra for Erectile Dysfunction?

Clinical trials demonstrate that sildenafil significantly improves erectile function across diverse patient populations. In pivotal studies involving over 3,000 men with erectile dysfunction of various causes, 69-82% of patients reported improved erections on the 100mg dose, compared to 18-25% on placebo [3].

The medication works for men with ED caused by psychological factors, diabetes, cardiovascular disease, spinal cord injury, and post-prostatectomy [3]. However, efficacy varies based on underlying cause — men with nerve damage from radical prostatectomy typically see lower response rates (43-60%) compared to those with vasculogenic or psychogenic ED [4].

Onset of action occurs within 30-60 minutes for most men, with peak plasma concentrations reached around 60 minutes after oral administration [2]. Effects typically last 4-5 hours, though this varies based on individual metabolism, age, and hepatic function. Our superintendent pharmacist, Tarun Kumar (GPhC 2233073), advises patients that consistent results often improve after several attempts as confidence builds and anxiety diminishes.

Factors That Influence Viagra's Effectiveness

High-fat meals can delay absorption by up to 60 minutes, though overall bioavailability remains unchanged [2]. Alcohol consumption may impair erectile function independently of the medication, potentially reducing effectiveness. Age-related changes in drug metabolism mean older patients may experience prolonged effects, while those with severe hepatic or renal impairment require dose adjustments.

Psychological factors play a significant role in treatment outcomes. Performance anxiety, relationship stress, and depression can all interfere with the medication's efficacy, even when the physiological mechanism is working correctly. Our UK prescribers assess these factors during consultation to ensure comprehensive treatment planning.

Viagra vs Sildenafil: Understanding the Difference

Viagra is the original branded version of sildenafil manufactured by Pfizer, while generic sildenafil contains the identical active ingredient at the same strength and formulation. When Pfizer's patent expired in 2013, multiple pharmaceutical manufacturers began producing licensed generic versions approved by the MHRA.

Both Viagra and generic sildenafil are bioequivalent, meaning they deliver the same amount of active drug to the bloodstream at the same rate [5]. Clinical efficacy, safety profile, and side effects are identical. The primary differences are price, packaging, and inactive ingredients (such as tablet colourants), which do not affect therapeutic action.

At Cured Pharmacy, we offer both branded Viagra Connect and generic sildenafil options. Generic sildenafil provides the same clinical benefits at a significantly lower cost, with prices starting from £0.45. All medications dispensed are genuine UK-licensed products sourced from MHRA-approved manufacturers, ensuring quality and safety regardless of whether you choose branded or generic treatment.

Treatment Active Ingredient Duration Starting Price
Sildenafil Sildenafil citrate 4-5 hours From £0.45
Viagra Connect Sildenafil citrate 4-5 hours From £11.49
Tadalafil Tadalafil Up to 36 hours From £9.99
Cialis Tadalafil Up to 36 hours From £53.00
Sildenafil Eropid Sildenafil citrate 4-5 hours From £8.99

How to Take Viagra Safely and Effectively

Viagra is available in 25mg, 50mg, and 100mg tablets. The standard starting dose recommended by NICE is 50mg, taken approximately one hour before sexual activity [6]. Based on efficacy and tolerability, your UK prescriber may adjust the dose to 25mg or increase it to the maximum 100mg dose.

The tablet should be swallowed whole with water and can be taken with or without food, though high-fat meals may delay onset. Viagra should not be taken more than once in a 24-hour period. For optimal results, take the medication on an empty stomach or after a light meal, and allow adequate time for absorption before sexual activity.

Sexual stimulation is essential for the medication to work — Viagra does not produce erections without arousal. Many patients find that the first few attempts yield better results as anxiety decreases and they become familiar with the medication's effects and timing.

Who Should Not Take Viagra

Viagra is contraindicated in men taking nitrate medications (such as glyceryl trinitrate for angina) due to risk of severe hypotension [1]. It should also be avoided in those taking riociguat for pulmonary hypertension. Men with severe cardiovascular disease, recent stroke or heart attack, or uncontrolled blood pressure require careful assessment before treatment.

Certain medications interact with sildenafil, including alpha-blockers, some antifungals, HIV protease inhibitors, and other drugs metabolised by the CYP3A4 enzyme pathway [2]. During your free online consultation at Cured Pharmacy, our UK prescribers review your complete medication history to identify potential interactions and determine the safest treatment approach.

Common Side Effects and How to Manage Them

The most frequently reported side effects of Viagra include headache (16% of patients), facial flushing (10%), dyspepsia (7%), nasal congestion (4%), and visual disturbances such as blue-tinted vision or increased light sensitivity (3%) [3]. These effects are generally mild to moderate, dose-dependent, and resolve within a few hours as the medication is metabolised.

Headaches occur because PDE5 inhibitors cause mild vasodilation throughout the body, not just in penile tissue. Taking the medication with adequate hydration and a mild analgesic like paracetamol can help manage this effect. Visual disturbances result from weak inhibition of PDE6 in the retina and are temporary, typically lasting 2-3 hours [2].

Serious adverse effects are rare but require immediate medical attention. These include priapism (erection lasting more than 4 hours), sudden vision loss, sudden hearing loss, and severe allergic reactions. If you experience chest pain during sexual activity after taking Viagra, stop and seek emergency medical care — do not take nitrates, as the combination can cause life-threatening hypotension [1].

Alternative Erectile Dysfunction Treatments Available

While sildenafil remains the most widely prescribed ED treatment in the UK, several alternatives offer different pharmacokinetic profiles that may better suit individual lifestyles and preferences. Tadalafil (the active ingredient in Cialis) has a significantly longer half-life of 17.5 hours, providing a window of up to 36 hours for spontaneous sexual activity [7]. This eliminates the need for precise timing before intercourse.

Tadalafil is also available as a low-dose daily medication (2.5mg or 5mg), allowing men to maintain continuous readiness without planning around tablet timing [7]. This approach may benefit those who prefer spontaneity or engage in sexual activity more than twice weekly. At Cured Pharmacy, we offer both on-demand and daily tadalafil options, with prices starting from £0.45.

Other PDE5 inhibitors include vardenafil and avanafil, though these are less commonly prescribed in UK clinical practice. For men who do not respond adequately to oral medications, alternative treatments include vacuum erection devices, intracavernosal injections, intraurethral suppositories, and penile prosthesis surgery. Your UK prescriber can discuss these options if first-line oral therapy proves insufficient.

Choosing Between Viagra and Tadalafil

The choice between sildenafil and tadalafil often comes down to lifestyle factors rather than efficacy, as both medications show similar success rates in clinical trials [7]. Men who prefer planned sexual activity and want effects to wear off relatively quickly may prefer sildenafil's 4-5 hour window. Those seeking weekend-long flexibility or who find timing stressful often prefer tadalafil's extended duration.

Cost is another consideration. Generic sildenafil typically offers the lowest per-dose price, making it economical for occasional use. Daily low-dose tadalafil may be more cost-effective for frequent sexual activity. Our transparent pricing at Cured Pharmacy allows you to compare options before completing your consultation, with no hidden fees or surprise charges at checkout.

Scientific References

  1. Boolell, M., Allen, M. J., Ballard, S. A., Gepi-Attee, S., Muirhead, G. J., Naylor, A. M., Osterloh, I. H., & Gingell, C. (1996). Sildenafil: an orally active type 5 cyclic GMP-specific phosphodiesterase inhibitor for the treatment of penile erectile dysfunction. International Journal of Impotence Research, 8(2), 47–52.
  2. Nichols, D. J., Muirhead, G. J., & Harness, J. A. (2002). Pharmacokinetics of sildenafil after single oral doses in healthy male subjects: absolute bioavailability, food effects and dose proportionality. British Journal of Clinical Pharmacology, 53(Suppl 1), 5S–12S. https://doi.org/10.1046/j.0306-5251.2001.00027.x
  3. Goldstein, I., Lue, T. F., Padma-Nathan, H., Rosen, R. C., Steers, W. D., & Wicker, P. A. (1998). Oral sildenafil in the treatment of erectile dysfunction. New England Journal of Medicine, 338(20), 1397–1404. https://doi.org/10.1056/NEJM199805143382001
  4. Montorsi, F., Nathan, H. P., McCullough, A., Brock, G. B., Broderick, G., Ahuja, S., Whitaker, J. S., Hoover, A., & Novack, D. (2004). Tadalafil in the treatment of erectile dysfunction following bilateral nerve sparing radical retropubic prostatectomy: a randomized, double-blind, placebo controlled trial. The Journal of Urology, 172(3), 1036–1041. https://doi.org/10.1097/01.ju.0000136448.86147.22
  5. Medicines and Healthcare products Regulatory Agency. (2013). Sildenafil: Generic Products Approved. Drug Safety Update, 6(11), A1. https://www.gov.uk/drug-safety-update
  6. National Institute for Health and Care Excellence. (2024). Erectile dysfunction. NICE Clinical Knowledge Summaries. https://cks.nice.org.uk/topics/erectile-dysfunction/
  7. Carson, C. C., & Lue, T. F. (2005). Phosphodiesterase type 5 inhibitors for erectile dysfunction. BJU International, 96(3), 257–280. https://doi.org/10.1111/j.1464-410X.2005.05614.x

Information on this page is for educational purposes only and is not medical advice. All prescription treatments require clinical assessment by a UK-registered prescriber. Always consult a qualified healthcare professional before starting any new medication. Viagra and sildenafil may not be suitable for everyone, particularly those with certain cardiovascular conditions or taking nitrate medications. Side effects can occur, and individual results may vary.

How it Works?

Select from our recommended UK-licensed medications.

1

Choose your treatment

Step 1: Choose your treatment from Cured Pharmacy

Select safe UK treatments. Quick answers.

2

Answer quick questions

Step 2: Answer quick consultation questions

We will deliver direct to you as quickly as tomorrow.

3

Get it delivered fast

Step 3: Fast discreet delivery to your door

Start Your Assessment For Erectile Dysfunction

Start your journey to better health today.

  • Reviewed by UK-based prescribers
  • Takes under 3 minutes
  • Discreet Packaging

Start Your Journey To Better Health Today

Once you complete a short online assessment you will be able to choose your preferred treatment from safe medically approved options tailored to you.

Start My Assessment

Returning Customer?

Log in to Your Account

Faq

What is Viagra and how does it work in the body?
Viagra contains sildenafil, a PDE5 inhibitor that enhances blood flow to the penis by preventing the breakdown of cGMP, a chemical that relaxes blood vessels. Sexual stimulation is required for the medication to work.
How long does Viagra take to work?
Viagra typically begins working within 30-60 minutes after oral administration, with peak effects around 60 minutes. High-fat meals can delay onset by up to an hour, so taking it on an empty stomach may produce faster results.
How long do the effects of Viagra last?
The effects of Viagra typically last 4-5 hours, though this varies based on individual metabolism, age, and liver function. The medication should not be taken more than once in a 24-hour period.
Is generic sildenafil as effective as branded Viagra?
Yes, generic sildenafil is bioequivalent to branded Viagra, containing the same active ingredient at identical strength. Clinical efficacy, safety, and side effects are the same, with generic versions offering significant cost savings.
What is the difference between Viagra and Cialis?
Viagra (sildenafil) lasts 4-5 hours, while Cialis (tadalafil) can remain effective for up to 36 hours. Both are PDE5 inhibitors with similar efficacy rates, but tadalafil offers more flexibility for spontaneous sexual activity.
Can I take Viagra with alcohol?
Moderate alcohol consumption is generally safe with Viagra, but excessive drinking can impair erectile function independently and may reduce the medication's effectiveness. Alcohol also increases the risk of side effects like dizziness and low blood pressure.
What are the most common side effects of Viagra?
The most common side effects include headache (16%), facial flushing (10%), indigestion (7%), nasal congestion (4%), and temporary visual disturbances (3%). These effects are usually mild and resolve within a few hours.
Do I need a prescription for Viagra in the UK?
Yes, all sildenafil products (including Viagra and Viagra Connect) require a clinical assessment by a UK-registered prescriber. At Cured Pharmacy, our free online consultation takes under 3 minutes, and prescriptions are issued the same day subject to approval.
Tarun Kumar, Prescribing Pharmacist

Medically reviewed by

Tarun Kumar, Prescribing Pharmacist (GPhC 2233073)

Last reviewed: 17 July 2026