Like all medicines, haloperidol can cause side effects, although not everyone gets them.
Common side effects
These common side effects of haloperidol happen in more than 1 in 100 people. They're usually mild and go away by themselves. There are things you can do to help cope with them:
Feeling dizzy or low blood pressure
Stop what you're doing and sit or lie down until you feel better. Do not drive, cycle or use tools or machinery.
This may improve as your body gets used to the medicine. If it does not improve, talk to your doctor. They may suggest changing to a different medicine, or taking a medicine for low blood pressure.
Constipation
Get more fibre into your diet, such as fresh fruit, vegetables and cereals, and drink plenty of water. Try to exercise more regularly, for example, by going for a daily walk or run. If this does not help, talk to your pharmacist or doctor.
Dry mouth
Try chewing sugar-free gum or sucking sugar-free sweets.
Blurred vision
Do not drive, cycle or use tools or machinery while this is happening. If it lasts for more than a day or 2, or it bothers you, speak to your doctor.
Feeling sleepy or drowsy
Do not drive, cycle or use tools or machinery. It's best not to drink alcohol, as it will make you feel more tired.
This may get better as your body gets used to the medicine. Talk to your doctor if it carries on for longer than a week. They may be able to suggest a different medicine.
Problems sleeping (insomnia)
Avoid having a big meal, smoking, or drinking tea or coffee in the evening. Try to go to bed and wake up at the same time each day. Try not to watch television or use your mobile phone before going to bed. Instead, try to relax for an hour before bedtime.
Speak to a doctor or pharmacist if the advice on how to cope does not help and a side effect is still bothering you or does not go away.
Serious side effects
Serious side effects are rare and happen in less than 1 in 10,000 people.
Call your doctor or call 111 straight away if you get:
- severe constipation, sometimes with severe stomach pain
- muscle stiffness or shaking
- problems with your movement, such as feeling restless or problems controlling the movement of your arms or legs
- uncontrollable movements of your face or tongue
- a sudden high temperature or an infection
- a fast or irregular heartbeat (your heart feels like it's pounding)
Immediate action required: Call 999 or go to A&E now if:
- you have had a seizure or fit
- you have a painful erection that lasts more than 2 hours – this may happen even when you're not having sex
Serious allergic reaction
In rare cases, it's possible to have a serious allergic reaction (anaphylaxis) to haloperidol.
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
Some people taking haloperidol for a long time get a movement disorder called tardive dyskinesia, which causes rhythmic movements of your tongue, face, mouth or jaw. Talk to your doctor if you get these symptoms.
Other side effects
These are not all the side effects of haloperidol. For a full list see the leaflet inside your medicines packet.
You can report any suspected side effect using the Yellow Card safety scheme.