Sildenafil

How it works

Sildenafil is a phosphodiesterase type-5 (PDE5) inhibitor. When you’re sexually stimulated, your body releases nitric oxide; sildenafil blocks the enzyme that breaks down the signal which relaxes blood vessels, so more blood flows into the penis and an erection becomes easier to get and keep. It only works alongside arousal — it isn’t an aphrodisiac and won’t cause an erection on its own.

Dosage & how to take it

Starting dose

50 mg, taken as needed about 1 hour before sex (anywhere from 30 minutes to 4 hours before).

Adjusting

Your prescriber may raise it to 100 mg or lower it to 25 mg based on effect and tolerance.

Maximum

100 mg, and no more than once in any 24-hour period.

With food

Can be taken with or without food; a heavy or high-fat meal may slow how quickly it works.

Duration

Typically effective for around 4–6 hours.

Important safety information — who should not take it

Common side effects

Most are mild and pass quickly. They include headache, facial flushing, a blocked or runny nose, indigestion, dizziness, and temporary changes to vision such as a blue tinge or light sensitivity. Stop and contact a clinician if side effects are severe or persistent.

Ingredients

Active ingredient: sildenafil (as sildenafil citrate), 25 mg, 50 mg or 100 mg per film-coated tablet. Inactive ingredients vary by licensed manufacturer and are listed on the patient information leaflet enclosed with every order.