Like all medicines, sildenafil can cause side effects, although not everyone gets them.
Common side effects
Common side effects of sildenafil happen in more than 1 in 100 people.
If you're taking it for erection problems you're unlikely to get side effects as you're only taking it for a short time.
If you're taking sildenafil for pulmonary hypertension and get these side effects, there are things you can do to help cope with them:
Headaches
Make sure you rest and drink plenty of fluids. Do not drink too much alcohol. Ask your pharmacist to recommend a painkiller. Headaches should usually go away after the first week of taking sildenafil. Talk to your doctor if they last longer than a week or are severe.
Feeling sick (nausea)
It may help if you avoid rich or spicy food. If you're taking sildenafil for pulmonary hypertension, it may help to take it after a meal or snack.
Flushing including hot flushes
Try cutting down on coffee, tea and alcohol. It might help to keep the room cool and use a fan. You could also spray your face with cool water or sip cold or iced drinks.
The flushing should go away after a few days. If it does not go away, or if it's causing you problems, contact your doctor.
Indigestion
If you need something to ease the discomfort, try taking an antacid, but do not put off going to the doctor if it bothers you. They may be able to prescribe an extra medicine to protect your stomach.
Stuffy nose
Speak to a pharmacist or doctor. They may be able to recommend a nasal spray that helps.
Feeling dizzy
If sildenafil makes you feel dizzy when you stand up, try getting up very slowly or stay sitting down until you feel better. If you begin to feel dizzy, lie down so that you do not faint, then sit until you feel better. Do not drive, cycle or use tools or machinery if you feel dizzy.
Tell your doctor or pharmacist if the advice on how to cope does not help or the side effects get worse.
Serious side effects
Serious side effects are rare and happen in less than 1 in 1,000 people.
Stop taking sildenafil and call your doctor or call 111 straight away if you have a sudden decrease or loss of vision.
Immediate action required: Call 999 or go to A&E now if:
- you or someone around you has a seizure or fit
- you have a prolonged or sometimes painful erection, especially if it lasts for more than 2 hours
Immediate action required: Call 999 now if:
- you get any chest pain
If this happens during or after sex and you are taking nitrates, do not take them to treat your chest pain.
Serious allergic reaction
In rare cases, it's possible to have a serious allergic reaction (anaphylaxis) to sildenafil.
Immediate action required: Call 999 now if:
- your lips, mouth, throat or tongue suddenly become swollen
- you're breathing very fast or struggling to breathe (you may become very wheezy or feel like you're choking or gasping for air)
- your throat feels tight or you're struggling to swallow
- your skin, tongue or lips turn blue, grey or pale (if you have black or brown skin, this may be easier to see on the palms of your hands or soles of your feet)
- you suddenly become very confused, drowsy or dizzy
- someone faints and cannot be woken up
- a child is limp, floppy or not responding like they normally do (their head may fall to the side, backwards or forwards, or they may find it difficult to lift their head or focus on your face)
You or the person who's unwell may also have a rash that's swollen, raised, itchy, blistered or peeling.
These can be signs of a serious allergic reaction and may need immediate treatment in hospital.
Other side effects
These are not all the side effects of sildenafil. For a full list, see the leaflet inside your medicine packet.
You can report any suspected side effect using the Yellow Card safety scheme.