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Medication guide
About sildenafil —
the active ingredient
30–60 min
Time to onset
4–6 hrs
Duration
25–200mg
Doses available
30+ yrs
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What is sildenafil?
Sildenafil citrate is the active ingredient in Viagra® and in every Cenforce tablet. It belongs to the class of drugs called PDE5 inhibitors. Originally developed by Pfizer, it became one of the most prescribed drugs in the world following FDA approval in 1998.
When the Pfizer patent expired, manufacturers worldwide were permitted to produce generic versions containing the exact same molecule — including Centurion Laboratories’ Cenforce range. The active ingredient is chemically identical; only the branding and price differ.
How sildenafil works
During sexual arousal, the body releases nitric oxide in penile tissue. This stimulates production of cGMP, which relaxes smooth muscle walls of blood vessels and allows blood to flow into the penis.
In men with ED, the enzyme PDE5 breaks down cGMP too quickly, reducing blood flow. Sildenafil blocks PDE5 — allowing cGMP to accumulate and blood flow to be maintained during sexual stimulation. Crucially, sildenafil only works with sexual arousal. It does not cause automatic erections.
Which dose should I take?
25mg or 50mg
100mg (most common)
150mg
For men who have tried 100mg and found it insufficient. Use under medical guidance.
200mg
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Side effects
Sildenafil is generally well tolerated. Common side effects (affecting 1–10% of users) include headache, flushing, indigestion, and nasal congestion. These are usually mild and temporary.
Seek emergency care immediately if you experience chest pain, sudden vision loss, or a prolonged erection (over 4 hours).
Critical warning: Never take sildenafil with nitrate medications (used for chest pain such as nitroglycerin, isosorbide). This combination can cause a dangerous and potentially fatal drop in blood pressure.
Dr. James Mitchell, PharmD, MBA
Lead Pharmacist · Reviewed May 2025
The most common question I get is "will sildenafil work for me?" For most men with no serious cardiovascular contraindications, the answer is yes — PDE5 inhibitors are effective in over 90% of ED cases. Start with 50–100mg, give it a fair trial of 3–4 attempts, and ensure you're taking it correctly: on a light stomach, with minimal alcohol, and with adequate sexual stimulation. The most common reason it "doesn't work" is incorrect technique, not the medication.