Like all medicines, lamotrigine can cause side effects, although not everyone gets them.
Most side effects of lamotrigine wear off, but it can take several weeks or months.
When you start taking lamotrigine, it's important to increase the dose slowly as this will help reduce or stop some side effects happening.
Lamotrigine can also cause some unpredictable side effects no matter what dose you take, and these can happen at any time.
Speak to your pharmacist or doctor if you're concerned about side effects.
Common side effects
These common side effects of lamotrigine may happen in more than 1 in 10 people. There are things you can do to help you cope:
Headaches
Make sure you rest and drink plenty of fluids. Do not drink too much alcohol. Ask your pharmacist to recommend a painkiller.
Talk to your doctor if your headaches last longer than a week or are severe.
Feeling drowsy, sleepy or dizzy
As your body gets used to lamotrigine, these side effects should wear off. Do not drive, ride a bike or operate machinery until you feel more alert.
If they do not go within a week or two, your doctor may reduce your dose or increase it more slowly. If that does not work, speak to your doctor. You may need to switch to a different medicine.
Aggression, or feeling irritable or agitated
Talk to your doctor.
Shaking or tremors
Talk to your doctor if this is bothering you. These symptoms can be a sign that the dose is too high for you. It may help to change your dose or take your medicine at a different time of day.
Difficulty sleeping
Talk to your doctor.
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. Speak to a doctor if symptoms get worse or last longer than a week.
If you take contraceptive pills and you have severe diarrhoea for more than 24 hours, your contraception may not protect you from pregnancy. Check the pill packet to find out what to do.
Feeling or being sick (nausea or vomiting)
Stick to simple meals and do not eat rich or spicy food. It might help to take your lamotrigine after a meal or snack. If you're being sick, take small, frequent sips of water or squash to avoid dehydration.
Speak to a doctor if symptoms get worse or last longer than a week.
If you take contraceptive pills and you're being sick, your contraception may not protect you from pregnancy. Check the pill packet to find out what to do.
Mild skin rash
If you get a mild rash speak to your doctor for advice as your treatment may need to be changed.
Also see our serious side effects information.
If this advice does not help and you are bothered by any of these side effects, keep taking the medicine but tell your doctor or pharmacist.
Serious side effects
Skin rashes
It's common to get a skin rash with lamotrigine. Most skin rashes are not serious.
Stevens-Johnson syndrome is a rare side effect of lamotrigine.
It causes flu-like symptoms, followed by a red or purple rash that spreads and forms blisters. The affected skin eventually dies and peels off.
It's more likely to happen in the first 8 weeks of starting lamotrigine, or when the dose is increased too quickly.
It can also happen if lamotrigine is stopped suddenly for a few days and then restarted at the same dose as before, without reducing the dose and then increasing it slowly again.
Stevens-Johnson syndrome is more common in:
- children
- people who have developed a rash before with a different epilepsy medicine
- people who are allergic to an antibiotic called trimethoprim
- people also taking a medicine called sodium valproate
To help reduce the chance of you getting a rash that could be confused with Stevens-Johnson syndrome, it's best to not try any new medicines or food during the first 3 months of treatment with lamotrigine.
Immediate action required: Go to A&E now if:
- you get a severe rash with flushing, blisters or ulcers – these can be signs of Stevens-Johnson syndrome
Other serious side effects
Very few people taking lamotrigine have any serious problems as any serious reaction is quite rare.
Tell a doctor or call 111 straight away if you have a serious side effect, including:
- worsening fits or seizures (if you take lamotrigine for epilepsy)
- unexpected bruising or bleeding, a high temperature or sore throat – these could be signs of a blood disorder
Immediate action required: Go to A&E or call 999 now if:
- you have thoughts of harming or killing yourself – a small number of people taking lamotrigine for bipolar disorder have had suicidal thoughts, and this can happen after only a few weeks of treatment
- you have a stiff neck, headaches, feel or are being sick, a high temperature and extreme sensitivity to bright light – these could be signs of meningitis
Serious allergic reaction
In rare cases, it's possible to have a serious allergic reaction (anaphylaxis) to lamotrigine.
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.
Long-term side effects
There have been reports of osteoporosis and osteopenia in people taking lamotrigine for a long time. Both these conditions increase your risk of breaking a bone.
Your doctor can arrange for tests to check your bone strength.
Regular exercise and a good diet can also help keep your bones strong.
Other side effects
These are not all the side effects of lamotrigine. For a full list, see the leaflet inside your medicine packet.
You can report any suspected side effect using the Yellow Card safety scheme.