Like all medicines, varenicline can cause side effects, although not everyone gets them.
Common side effects of varenicline
Varenicline can have side effects, but there are things you can do to help cope with them.
Sore or swollen (inflamed) nose or throat
Try taking an anti-inflammatory medicine like ibuprofen for a few days.
Headaches
Make sure you rest and drink plenty of fluids. Try not drink too much alcohol. Painkillers such as paracetamol and ibuprofen can also help. Talk to your doctor if the headaches last several days or are severe.
Diarrhoea
Drink lots of fluids, such as water or squash, to avoid dehydration. Signs of dehydration include peeing less than usual or having dark* strong-smelling pee. Do not take any other medicines to treat diarrhoea without speaking to a pharmacist or doctor.
If you take the combined contraceptive pill or progestogen-only pill and you have severe, watery diarrhoea, or any diarrhoea that lasts for more than 24 hours, your contraception may not protect you from pregnancy. Check the pill packet for advice.
Heartburn (acid reflux)
It may help to avoid rich and spicy food, and not eating just before going to bed. Sleeping with the head of your bed raised, can also help symptoms. If these do not help, try asking a pharmacist about suitable antacids to take.
Difficulty sleeping (insomnia)
If you’re having difficulty sleeping, speak to a doctor.
Feeling dizzy
If you feel dizzy, sit or lie down until you feel better. If this continues and you cannot cope, your doctor may reduce your dose.
Do not drive, cycle or use tools or machinery until you feel OK again.
Try to avoid alcohol as it will make you feel worse.
A bad taste in your mouth
Talk to your doctor if this side effect bothers you or does not go away.
If this advice does not help and any of these side effects bother you, talk to your doctor or pharmacist.
Serious side effects
Serious side effects are rare but can happen.
Call a doctor or contact 111 now if you:
- start to feel irritable, aggressive, anxious or experience changes to your heart rate (palpitations)
Immediate action required: Call 999 or go to A&E if:
- you have thoughts about harming yourself or ending your life
- you have had a seizure or a fit
- you get weakness on one side of your body, trouble speaking or thinking, loss of balance or blurred eyesight - these can be signs of a stroke
- you get chest pain or shortness of breath - these may be signs of a heart attack
Do not drive yourself to A&E.
The person you speak to at 999 will give you advice about what to do.
Serious allergic reaction
In rare cases, it's possible to have a serious allergic reaction (anaphylaxis) to varenicline.
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.
Do not drive yourself to A&E.
The person you speak to at 999 will give you advice about what to do.
Other side effects
These are not all the side effects of varenicline. For a full list see the leaflet inside your medicines packet.
Reporting side effects
You can report any suspected side effect using the Yellow Card safety scheme.
Visit the Yellow Card website for more information about reporting side effects.