Like all medicines, loperamide can cause side effects, but many people have no side effects or only minor ones.
Common side effects
These common side effects of loperamide happen in more than 1 in 100 people. There are things you can do to help cope with them:
Constipation
If you have difficulty doing a poo, stop taking loperamide.
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.
Feeling sick (nausea)
Try taking loperamide with or after a meal or snack. It may also help if you avoid rich or spicy food.
Headaches
Make sure you rest and drink plenty of fluids. Try to avoid drinking alcohol. Ask your pharmacist to recommend a painkiller.
Talk to your doctor if the headaches last longer than a week or are severe.
Farting
Avoid foods that cause farting (flatulence) like lentils, beans and onions. It might also help to eat smaller and more frequent meals, eat and drink slowly, and exercise regularly.
There are products you can buy from a pharmacy to help with farting. Loperamide can be bought mixed with simeticone, a medicine that helps relieve bloating, farting and cramping.
Speak to a pharmacist or doctor 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
It's rare to have a serious side effect with loperamide.
Stop taking loperamide and speak to a doctor or call 111 straight away if you:
- feel faint or less alert, or if you pass out (faint)
- start moving in a clumsy, uncoordinated way
- have stomach pain or tenderness, a high temperature, a fast pulse, or are being sick – these may be symptoms of an inflamed pancreas
- have severe constipation
- are having difficulties peeing
Serious allergic reaction
It happens rarely, but it's possible to have a serious allergic reaction (anaphylaxis) to loperamide.
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 loperamide. For a full list, see the leaflet inside your medicines packet.
You can report any suspected side effect using the Yellow Card safety scheme.