Understanding the PDE5 Inhibition Mechanism
The Biological Process of Erectile Function
To understand how sildenafil works, it's essential to understand normal erectile function. When sexually aroused, the brain sends signals that trigger the release of nitric oxide in penile blood vessels. This nitric oxide activates an enzyme called guanylate cyclase, which produces cyclic guanosine monophosphate (cGMP). The cGMP causes smooth muscle relaxation in blood vessels, allowing increased blood flow into the penis to create an erection.
How PDE5 Enzyme Affects Erections
Phosphodiesterase type 5 (PDE5) is an enzyme that naturally breaks down cGMP, ending the erection. In men with erectile dysfunction, this process may occur too quickly or the initial blood flow response may be insufficient. Research published in medical journals shows that sildenafil selectively inhibits the PDE5 enzyme, preventing the premature breakdown of cGMP and maintaining improved blood flow for longer periods.
Sildenafil's Mechanism of Action
Sildenafil citrate works by binding to the PDE5 enzyme and blocking its activity. This selective inhibition allows cGMP levels to remain elevated for longer, promoting sustained blood vessel dilation in the penis. Clinical studies demonstrate that sildenafil is highly selective for PDE5, with minimal effects on other phosphodiesterase enzymes, which explains its targeted effectiveness for erectile dysfunction whilst reducing unwanted side effects.
Timeline and Effectiveness
Scientific studies show sildenafil typically begins working within 30-60 minutes of oral administration. Peak plasma concentrations occur approximately 60 minutes after taking the medication on an empty stomach. The effects can last 4-6 hours, though this doesn't mean an erection persists for this duration. The medication simply makes it easier to achieve and maintain erections when sexually aroused during this timeframe.
Dosage and Personalisation
EverydayMeds offers sildenafil in three strengths: 25mg, 50mg, and 100mg. The standard starting dose is typically 50mg, taken approximately one hour before sexual activity. Based on effectiveness and tolerability, the dose may be adjusted. Clinical evidence supports taking no more than one dose per 24-hour period. Our UK-licensed prescribers evaluate individual circumstances during the online consultation to determine the most appropriate starting dose.
Branded Viagra vs Generic Sildenafil
Both branded Viagra and generic sildenafil contain the same active ingredient - sildenafil citrate - and work through identical mechanisms. Clinical studies confirm bioequivalence between branded and generic formulations. At checkout, patients can choose between Viagra (branded) or generic sildenafil, with the generic option typically offering cost savings whilst maintaining the same therapeutic effectiveness and safety profile.
