Standard dosing
The standard starting dose is 50 mg taken 30–60 minutes before sexual activity. If 50 mg is well tolerated but not effective enough, the dose can be increased to 100 mg. If 50 mg causes side effects, reducing to 25 mg is appropriate. Do not take more than once in 24 hours.
Timing matters
Take sildenafil on an empty stomach or after a light, low-fat meal. A high-fat meal (e.g., fish and chips, cheeseburger) delays absorption significantly — you may not feel the effect for 2 hours or more. This is the most common reason sildenafil “doesn’t work” in real-world use.
Alcohol
Both alcohol and sildenafil lower blood pressure. Combining them raises the risk of dizziness and fainting. Limit alcohol to 1–2 units before taking sildenafil.
What not to take it with
Never combine sildenafil with nitrates (GTN spray, isosorbide mononitrate, recreational poppers). The combination can cause a severe, potentially fatal drop in blood pressure. Also avoid riociguat (a sGC stimulator used for pulmonary hypertension).
When it might not work
Sildenafil requires sexual stimulation to work. If there is no arousal response, the drug cannot produce an erection. Anxiety, relationship issues, and low testosterone are common reasons for apparent treatment failure. Give it 4–8 attempts before concluding it is not effective.
Henry Thomas is a licensed clinical pharmacist with 15 years of experience. He holds a B.Pharm and M.Pharm from Mahatma Gandhi University. At OnlineMeds, he reviews medicine and health content to help ensure it is accurate, evidence-based, and easy to understand.