Like all medicines, clonidine can cause side effects in some people, although not everyone gets them.
Side effects often improve as your body gets used to the new medicine.
Older people are more sensitive to the side effects of clonidine.
Common side effects
These common side effects of clonidine happen in more than 1 in 100 people. These side effects do not usually last long and there are things you can do to help cope with them:
Feeling sleepy, tired and weak
Make sure you rest and allow your body time to get used to clonidine.
Do not drive, cycle or use tools or machinery if you’re feeling sleepy.
Do not drink alcohol as it will make you feel worse.
If you take clonidine once a day and you get this side effect, you may prefer to take it around bedtime.
These side effects usually wear off, but if it bothers you or lasts more than a week, speak to your doctor.
Feeling dizzy or faint when you stand up
Speak to your doctor straight away if you have fainted.
If you're feeling dizzy when you stand up, stop what you're doing and sit or lie down until you feel better.
Do not drive, cycle or use tools or machinery if you're feeling dizzy.
Do not drink alcohol as this can also cause low blood pressure and will make you feel worse.
If the dizziness does not get better within a few days, speak to your pharmacist or doctor.
Dry mouth
Drink plenty of cool water, taking regular sips during the day and keep some water by your bed at night. Suck on ice cubes or ice lollies. Sip on cold, unsweetened drinks. Chew sugar-free gum or suck on sugar-free sweets.
Use lip balm if your lips are also dry. Brush your teeth twice a day and use alcohol-free mouthwash.
Ask a pharmacist about treatments you can buy to help keep your mouth moist, such as gels, sprays, tablets or lozenges.
Speak to your doctor if:
- your mouth is still dry after trying home or pharmacy treatments
- you're having difficulty chewing
- your sense of taste is affected
- your mouth is painful, swollen, red or bleeding
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.
Erection problems (erectile dysfunction or impotence)
Consider whether there may be other causes of erectile dysfunction that may be making the problem worse. Other causes could include stress, anxiety, tiredness, being overweight or drinking too much alcohol.
Make sure you eat a healthy diet, limit or avoid alcohol, and exercise daily. Try to reduce stress and anxiety, and quit smoking and lose weight if you’re overweight.
Speak to your doctor if erectile dysfunction continues for more than a few weeks. You may need to stop taking clonidine and try a different medicine. Do not stop taking clonidine suddenly as this can cause dangerously high blood pressure and other side effects.
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 clonidine. Talk to your doctor if they last longer than a week or are severe.
Depression
Speak to your GP if you have low mood, sadness or depression.
Difficulty sleeping
Avoid having a big meal, smoking, or drinking alcohol, tea or coffee in the evening. 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 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
Serious side effects of clonidine are uncommon and happen in less than 1 in 100 people.
Call a doctor or call 111 now if you get:
- heart problems such as an irregular heartbeat or heart palpitations, or an unusually slow heartbeat (bradycardia)
- feelings of confusion, problems understanding what is happening around you, or hallucinations (seeing or hearing things that are not real)
- stomach pain, vomiting and constipation symptoms all together – these can be symptoms of a rare condition called pseudo-obstruction of the large bowel
Serious allergic reaction
In rare cases, clonidine may cause a serious allergic reaction (anaphylaxis).
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 clonidine. For a full list see the leaflet inside your medicine packet.
You can report any suspected side effect using the Yellow Card safety scheme.