Like all medicines, duloxetine can cause side effects in some people. But most people have no side effects or only minor ones.
Some of the common side effects of duloxetine will gradually improve as your body gets used to it.
Common side effects
These common side effects of duloxetine can happen in up to 1 in 10 people. There are things you can do to help cope with them:
Difficulty sleeping
Try taking duloxetine first thing in the morning.
Headaches
Make sure you rest and drink plenty of fluids. Try not to drink too much alcohol. Ask your pharmacist to recommend a painkiller. Talk to your doctor if the headaches last longer than a week or are severe.
Feeling dizzy
If duloxetine makes you feel dizzy when you stand up, try getting up very slowly or stay sitting down until you feel better. If you begin to feel dizzy, lie down so you do not faint, then sit until you feel better. Do not drive, cycle or use tools or machinery if you feel dizzy.
Blurred vision
Avoid driving, cycling or using tools or machinery while this is happening. If it lasts for more than a day or two, your doctor may need to change your treatment.
Constipation
Try to get more fibre into your diet, such as fresh fruit and vegetables and cereals, and drink plenty of water. Try to exercise more regularly, for example by going for a daily walk or run.
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 the progestogen-only pill and you have severe diarrhoea for more than 24 hours, your contraception may not protect you from pregnancy. Check the pill packet for advice.
Feeling or being sick (nausea or vomiting)
Stick to simple meals and do not eat rich or spicy food. Make sure you take duloxetine in the morning with some food. Try small, frequent sips of water if you're being sick to avoid dehydration. Signs of dehydration include peeing less than usual or having dark, strong-smelling pee.
If you take the combined contraceptive pill or the progestogen-only pill and you're being sick, your contraception may not protect you from pregnancy. Check the pill packet for advice.
Dry mouth
Chew sugar-free gum or suck sugar-free sweets.
Sweating
Try wearing loose clothing, use a strong anti-perspirant, and keep cool using a fan if possible. If this does not help, you may need to try a different type of antidepressant.
Tiredness
Do not drive, cycle or use tools or machinery if you're feeling this way. Try taking duloxetine 1 hour before bedtime. Cut down the amount of alcohol you drink as alcohol will make you feel more tired.
If the tiredness does not go away after 2 weeks, ask your doctor for advice.
Less appetite than usual and weight loss
This side effect should get better as your body gets used to the medicine. It may also help to eat smaller meals more often and eat foods you really enjoy. If your appetite does not improve or you lose a lot of weight, ask your doctor for advice.
Feeling less interested in sex, or having problems keeping an erection or reaching orgasm
Speak to your doctor if you get this side effect and it does not go away.
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 100 people.
Book an appointment with your doctor if you get changes in your periods, such as heavy bleeding, spotting or bleeding between periods.
Call a doctor or call 111 straight away if you have:
- hallucinations (seeing or hearing things that are not real), or you become aggressive and angry
- feelings of euphoria, excessive enthusiasm or excitement, or feeling restless so that you cannot sit or stand still
- constant headaches, long-lasting confusion or weakness, or frequent muscle cramps – these can be signs of low sodium levels in your blood
- yellowing of the whites of your eyes, or your skin although this may be less obvious on brown or black skin – these can be signs of a liver problem
- eye pain or blurred vision
- black or red poo or blood in your vomit – these can be signs of bleeding from your gut
- coughed up blood or have blood in your pee
- bleeding from your gums, or bruises that appear without a reason or get bigger
Immediate action required: Call 999 or go to A&E now if you get:
- tightness in your chest or shortness of breath
- any heavy bleeding that you cannot stop, such as cuts or nosebleeds that do not stop within 10 to 15 minutes
- painful erections that last longer than 2 hours – this may happen even when you're not having sex
- thoughts about harming yourself or ending your life
Serious allergic reaction
In rare cases, it's possible to have a serious allergic reaction (anaphylaxis) to duloxetine.
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 duloxetine. For a full list, see the leaflet inside your medicines packet.
You can report any suspected side effect using the Yellow Card safety scheme.