What Is Viagra? Your Complete Guide to Sildenafil

Viagra — the world’s most recognised erectile dysfunction medication — has helped millions of men since its introduction in 1998. With over 65% of men reporting improved erections after taking it, Viagra (sildenafil) remains a first-line treatment for ED. But what exactly does Viagra do, how does it differ from generic sildenafil, do you need a prescription, and how do you take it safely? This comprehensive guide answers all of these questions.

What Does Viagra Do?

Viagra’s active ingredient, sildenafil, is a PDE5 inhibitor (phosphodiesterase type 5 inhibitor). Here is what happens after you take it:

• Sildenafil inhibits the PDE5 enzyme, which normally breaks down a compound called cyclic GMP (cGMP) in the smooth muscle of penile blood vessels
• When PDE5 is blocked, cGMP accumulates, causing smooth muscle to relax
• Relaxed smooth muscle allows blood vessels to widen (vasodilation)
• When sexually stimulated, this enables significantly increased blood flow into the erectile tissue of the penis
• The penis fills with blood and becomes erect
• Without sexual stimulation, Viagra has no effect — it enhances the natural response to arousal rather than bypassing it

Viagra vs Generic Sildenafil — Is There a Difference?

No. Branded Viagra and generic sildenafil are in complete bioequivalence — they contain the same active ingredient at the same dose, work through the same mechanism, last the same duration, and have the same side effect profile. Generic sildenafil became available in the UK after Pfizer’s patent expired in 2012 and is typically available at a significantly lower price.

Do You Need a Prescription for Viagra?

Since 2017, men can purchase sildenafil 50mg (Viagra Connect) without a prescription from a licensed UK pharmacy following a short pharmacist consultation. However, access to all doses and full clinical oversight requires a prescriber consultation. Access Doctor provides this online — our GPhC-registered pharmacist independent prescribers assess your health history, screen for contraindications, and issue prescriptions for the most appropriate dose.

How to Take Viagra Correctly

Who Should Not Take Viagra?

• Men taking nitrate medicines for chest pain (e.g., glyceryl trinitrate, isosorbide mononitrate) — this is an absolute contraindication due to the risk of severe blood pressure drop
• Men with severe cardiovascular disease or who have been advised to avoid sexual activity for cardiac reasons
• Men with severe liver or kidney disease
• Men with a known allergy to sildenafil
• Men with hereditary degenerative retinal disorders