Sildenafil is a selective PDE5 inhibitor developed in the 1990s to improve blood flow through vasodilation.
It was initially researched for cardiovascular conditions but soon became widely used for treating erectile dysfunction (ED) due to its strong effect on penile circulation.
By blocking the enzyme PDE5, sildenafil increases the level of cyclic guanosine monophosphate (cGMP) — a molecule responsible for relaxing smooth muscle cells in the vascular walls.
This process allows for better blood flow to specific tissues, particularly in the corpus cavernosum of the penis, resulting in improved erectile response.
Besides sexual health, sildenafil is sometimes used off-label to improve exercise tolerance and pulmonary function in patients with certain vascular disorders.
Main effects of sildenafil
💊 Improves erectile function and duration
🩸 Enhances blood circulation through vasodilation
⚡ Increases nitric oxide signaling and vascular responsiveness
💪 Supports physical endurance and oxygen delivery
🧠 May improve confidence and psychological well-being
How to take sildenafil
Administration
Route: oral, with water
Take approximately 30–60 minutes before sexual activity
May be taken with or without food, though high-fat meals can delay onset
Duration of effect: up to 4–5 hours
Dosage
Standard dose: 50 mg as needed, not more than once daily
Depending on individual response, dosage may be adjusted to 25 mg or 100 mg
Do not combine sildenafil with nitrate medications or other PDE5 inhibitors, as this can cause a dangerous drop in blood pressure.
Possible side effects
Headache or facial flushing
Nasal congestion
Indigestion or mild stomach discomfort
Dizziness or light-headedness
Vision changes (blue tint or blurred vision)
Rare: priapism (prolonged erection), hearing loss, or allergic reaction
Contraindications
Concomitant use of nitrates or nitric oxide donors
Severe cardiovascular or hepatic conditions
Hypotension or uncontrolled hypertension
Recent stroke or myocardial infarction
Known hypersensitivity to sildenafil or any excipients
How to store
Store at 20–25 °C (68–77 °F)
Keep in a dry, dark place, away from moisture and heat
Do not use past the expiration date
Keep out of reach of children
How does sildenafil work
Sildenafil enhances nitric oxide–mediated vasodilation by inhibiting the phosphodiesterase type 5 (PDE5) enzyme.
Under sexual stimulation, nitric oxide (NO) is released in penile tissue, increasing cGMP concentration.
This molecule relaxes smooth muscle cells and allows blood to flow more easily into the corpus cavernosum, creating and maintaining an erection.
By preventing cGMP degradation, sildenafil prolongs the duration of vasodilation, resulting in improved erectile quality and performance.
Its effects are systemic but most prominent in vascular tissues rich in PDE5, such as the lungs and corpus cavernosum.
Because of its predictable pharmacokinetics and relatively short half-life (~4 hours), sildenafil remains one of the most commonly used and well-studied agents for safe, effective management of erectile dysfunction and related circulatory issues.
