Also sold as Viagra · Written by the Lyng Pharmacy team, based on NHS and BNF guidance · Updated August 2026
Also sold asViagra, Viagra Connect
Type of medicinePDE5 inhibitor
Available asTablets
How you get itPharmacy (Viagra Connect) and prescription
Sildenafil improves blood flow to the penis in response to arousal — it does not create desire, and it does nothing without stimulation. It is available from pharmacies as Viagra Connect after a short consultation, and the consultation is not a formality: there are combinations that are genuinely dangerous.
How to take it
Take one tablet around an hour before sex, though it can work from about 30 minutes. It stays effective for around four hours.
A heavy or fatty meal delays absorption noticeably — take it on a relatively empty stomach if you can. Alcohol in quantity makes it less likely to work.
Take no more than one dose in 24 hours. If it does not work the first time, it is worth trying on several occasions before concluding it is ineffective, and the dose may need adjusting.
The interaction that matters
Never take sildenafil with nitrates — including GTN spray or tablets, isosorbide mononitrate or dinitrate — or with nicorandil, or recreational “poppers” (amyl nitrite). The combination causes a catastrophic drop in blood pressure and can be fatal.
Also tell us before use if you take alpha blockers such as tamsulosin, riociguat, some antifungals, HIV medicines, or clarithromycin.
Who should not take it
Recent heart attack or stroke, or unstable angina
Severely low blood pressure, or uncontrolled high blood pressure
Severe liver disease
A previous non-arteritic anterior ischaemic optic neuropathy — sudden loss of vision in one eye
Certain inherited eye conditions such as retinitis pigmentosa
If exercise makes you breathless or brings on chest pain, get that assessed before using sildenafil — sex is exercise.
Side effects, and why it is worth seeing a GP
Headache, flushing, indigestion, a blocked nose, dizziness and blue-tinged or blurred vision are the common effects and usually mild.
Seek urgent help for an erection lasting more than four hours, sudden loss of vision or hearing, or chest pain during sex — and if chest pain occurs, tell the paramedics you have taken sildenafil, because nitrates must be avoided.
Erectile dysfunction is frequently an early sign of cardiovascular disease, and is also associated with diabetes, low testosterone, depression and medication side effects. Treating it without investigating the cause misses something worth knowing. Ask your GP for a check even if the tablets work.
Always read the label. This page is general information, not advice for your situation. Doses, warnings and interactions differ between products and between people. Check the leaflet inside your medicine, and ask our pharmacist if anything is unclear — that conversation is free and takes two minutes.
Questions about Sildenafil?
1 Lyng Lane, West Bromwich B70 7RW · Mon–Fri 8:30am–6pm, Sat 9am–1pm · 0121 500 5756
Yes — Viagra Connect is available from pharmacies after a short consultation with the pharmacist.
What must I never take with sildenafil?
Nitrates such as GTN spray, isosorbide, nicorandil, or recreational poppers. The combination causes a dangerous drop in blood pressure and can be fatal.
How long before sex should I take sildenafil?
About an hour, though it can work from 30 minutes and lasts around four hours. A fatty meal delays it.
Should I see a GP about erectile dysfunction?
Yes. It is often an early sign of cardiovascular disease and is linked to diabetes, low testosterone and depression — worth investigating even if the tablets work.
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