Duloxetine

How it works

What does duloxetine do?

Duloxetine is a type of serotonin-noradrenaline reuptake inihibitor (SNRI).

(N.B. Noradrenaline is sometimes known as norepinephrine.)

Research suggests that depression is more likely to occur when the brain doesn’t have enough of the chemicals serotonin (also called ‘5HT’) and noradrenaline.

Nerve endings in the brain release these chemicals and take them back up again after they have targeted their receptors in what is known as a recycling process.

Serotonin-noradrenaline reuptake inhibitors (SNRIs) – like duloxetine - work by blocking recycling of released serotonin and noradrenaline back into the nerve endings.

This increases the amount of serotonin and noradrenaline, which helps treat the symptoms.

How long does duloxetine take to start working?

It takes two to four weeks for duloxetine to start helping. It could take some weeks or months to get its full effect.

Scientists believe that at first the higher levels of serotonin (and possibly noradrenaline) have direct effects which do not help relieve the depression or anxiety. In fact, you are likely to feel a bit more anxious or on edge for a couple of weeks. After some days of regular treatment, the brain adapts, which leads to improvements in mood and anxiety.

Your doctor might start you on a low dose and then increase it slowly over two to four weeks to your full dose.

How long will I need to take duloxetine?

You and your doctor should talk about how long you need to take duloxetine before you begin your treatment.

If there has been no good effect after four weeks on duloxetine, it is probably not the best medicine for your condition.

People normally take duloxetine until they feel better (around one to two months) then continue to take it for a further six to 12 months, as advised by their doctor, to avoid symptoms returning.

Your doctor needs to know if...

You need to talk to your doctor or pharmacist before starting treatment with duloxetine if any of the following apply to you:

• you have eye problems, such as certain kinds of glaucoma (increased pressure in the eye)
• you have low sodium levels in your blood, seen in tests (hyponatremia)
• you tend to develop bruises or to bleed easily (bleeding disorders)
• you have experienced mania (feeling over-excited or unusually happy)
• you have bipolar disorder (feeling over-excited or extremely happy, and then sometimes feeling very low)
• you have kidney or liver problems
• you have heart problems
• you have had seizures (fits) in the past or have been diagnosed with epilepsy
• you have had thoughts of harming yourself and/or taking your own life, or you have harmed yourself or attempted to take your own life in the past
• you have an allergy to duloxetine or other ingredients in tablets and capsules

Taking duloxetine

You should only take duloxetine as agreed with your doctor

You will get the best effect from duloxetine if you take it regularly at the dose prescribed by your doctor.

Make sure that you know your dose. If it is not written on the label, check with your pharmacist or doctor.

People usually take duloxetine once a day at the same time. This could be a mealtime, or when you brush your teeth.

If you are taking duloxetine for depression, you are likely to start taking it at the standard treatment dose. If you are taking it for anxiety, you may be started on a lower dose, which gets increased gradually.

You can take duloxetine before or after food.

Swallow the capsule with a drink of water - if you chew it, it tastes bitter.

What if I miss a dose?

If you remember later during the day, take it as soon as possible.

If you forget to take it by the time of your next dose, only take the next dose.

Do not take a double dose. 

What will happen if I forget to take my duloxetine?

If you forget to take it for a few days, you may start getting withdrawal symptoms. Talk to your doctor if this is the case.

Stopping the use of duloxetine

Once you start taking a medicine like duloxetine, the brain adjusts to having new levels of serotonin and noradrenaline around. If you stop taking duloxetine all at once, the balance starts to change again. You could get some unpleasant symptoms from the change.

It is better to discuss stopping with a doctor who will reduce your dose gradually over at least four weeks.

Some of the symptoms you might get include:

• dizziness
• headaches
• tingling feelings like pins and needles, or electric shocks (particularly in the head)
• sleep disturbances (vivid dreams, nightmares, not being able to sleep)
• feeling anxious, restless, agitated or irritable
• feeling sick or being sick
• shaking
• feeling unusually tired or weary
• muscle pain
• diarrhoea (loose poo)
• excessive sweating
• vertigo (losing your balance)

These symptoms should stop after two weeks for most people, but some people can get them for two to three months or more.

Most people get mild symptoms, but for some people they can be very intense.

Go and speak to your doctor if you have missed a few doses or have decided to stop taking your medication.

When you agree with your doctor to stop the medicine, you will carry on with a lower dose for at least two weeks. This will lower your risk of getting withdrawal symptoms.

The information on this page was reviewed by the College of Mental Health Pharmacy in October 2019.

Safety headlines

If you have taken more duloxetine than the dosage recommended by the doctor who prescribed it to you, you must get medical help immediately – even if you do not feel any different.

As part of depression, some people think about hurting themselves or taking their own lives. Taking an antidepressant may not stop this. You must get urgent help if you are having these sorts of thoughts. Speak to someone who is looking after you or go straight to hospital with your tablets.

Do not take duloxetine if you have taken a monoamine oxidase inhibitor antidepressant (MAOI) like moclobemide, phenelzine, isocarboxazid or tranylcypromine in the last 14 days.

Stopping duloxetine suddenly can cause unpleasant withdrawal effects. Talk to your doctor if you want to stop, or if you are having these effects.

You may feel sleepy and your eyesight might be affected in the first few days after taking duloxetine. Do not drive a car, ride a bike or operate machines until you see how this affects you.

If you take duloxetine while you are pregnant, it may affect the developing baby. Use good contraception while you are taking duloxetine. It can also cause symptoms in newborn babies if you take it at the end of pregnancy. Talk to your doctor or midwife about this and get their help.

When to go to the hospital

If you have taken more duloxetine than the dosage recommended by the doctor who prescribed it to you, you must get medical help immediately – even if you do not feel any different. Go to A&E. Take your medicine with you to show to the doctors. Tell them how much you have taken. Get a friend or family member to go with you if you can in case you feel ill on the way. 

You might get any of the following signs:

• feeling sick or being sick
• having seizures (fits)
• an irregular heartbeat or a heart attack
• extreme sleepiness that could lead to a coma

You are also at risk of getting serotonin syndrome. Signs of serotonin syndrome include a high fever, agitation, confusion, trembling, feeling drunk or getting weird movements of your muscles. This is rare, but you should watch out for it.

Duloxetine can make some people think about hurting themselves or taking their own lives. This can happen to anyone, especially people who are under 18. You must go straight to hospital with your medicine if you have any of these thoughts. You must tell the doctor that you are taking duloxetine. There are other things you can take instead.

Stop taking duloxetine and go to a doctor or hospital straight away if you get any of the following symptoms:

• difficulty breathing; any rash and itching; or swelling of your face, lips, tongue or throat to the extent that you cannot swallow or breathe. This might be an allergic reaction 

Go to a doctor or hospital straight away, but do not stop taking your duloxetine, if you get any of the following symptoms

• a high temperature/fever, agitation, confusion, trembling or weird muscle movements. These may be signs of a rare condition called serotonin syndrome.
• tiredness, confusion and muscle twitching. You may have a low blood level of sodium
• your skin starts going red and blistering or peeling
• unexplained vaginal bleeding (like an unusual period)

Side effects

Most side effects that appear should get better after a few days. If they do not, you should go back to your doctor.

If you get any side effects not listed here please look at the patient leaflet in the medicine pack.

Do not stop taking the capsules until you talk to your doctor, or you may get withdrawal symptoms as well. 

Very common side effects of taking duloxetine (affecting more than one in ten people) include:

• headache
• feeling sleepy
• nausea (feeling sick)
• dry mouth

Common side effects of taking duloxetine (affecting one in ten people) include:

• loss of appetite 
• weight loss - Some children and young people aged under 18 who took duloxetine had some weight loss at first, but after six months of treatment they went back to normal compared with other people of the same age
• feeling nervous, anxious, restless, agitated or tense
• lower sex drive, or other sexual problems, including difficulty maintaining an erection (staying hard) and difficulty having an orgasm (coming)
• sleep problems, unusual dreams, tiredness or sleepiness
• feeling dizzy
• feeling sluggish (having low energy)
• uncontrollable shaking movements or feeling numb
• blurred eyesight
• feeling your heartbeat pumping in your chest, or higher blood pressure
• flushing red skin, sweating more
• yawning a lot
• tinnitus (ringing in the ears)
• indigestion, being sick, constipation or diarrhoea, stomach pain, or passing wind more often
• itchy skin rash, or skin prickling/tingling/numbness
• muscle pain or spasm
• going to wee more often, which may be painful
• falling (this happens mainly in older people) 

There are other side effects that you can get when taking this medicine. We have only included the most common ones here.

Please look at the leaflet inside your medicine box, or ask a doctor or pharmacist, if you want to know whether you are getting a side effect from your medicine.

If you do get a side effect, please think about reporting it via the Yellow Card Scheme.  

Body

A side effect of duloxetine can be not feeling as hungry as normal, which might lead to weight loss.

Some children and young people aged under 18 who took duloxetine had some weight loss at first, but after six months of treatment they went back to normal compared with other people of the same age.

It is very difficult to know how it will affect each person who takes it.

Talk to your doctor about this if it worries you.

Sleep

You can feel sleepy in the first few days of taking duloxetine. However, this should get better after the first week or two.

It can also give you sleep problems, including unusual dreams.

If you experience any of these side effects and have been taking duloxetine for more than a month, you should go back to the doctor and see what else you could do.

Sex and fertility

Sex

Duloxetine can have side effects that might affect your sex life. These include:

• problems getting an erection (getting hard) and ejaculating (coming)
• unusual bleeding from the vagina
• testicle pain
• changes in how you reach orgasm (come)
• you may have a lower sex drive
• growth of the breasts and some milk flow, regardless of gender

These effects should pass after the first couple of weeks. If they do not, and this is a problem for you, go back to the doctor and see what else you could try.

The good effects of duloxetine may, after a while, have a good effect on your sex life as your mood lifts and you become interested in life and relationships again.

Fertility

In tests, duloxetine did not affect male fertility, and only affected female fertility at doses much higher than we would normally see.

You should use good contraception when you are taking duloxetine. Talk to your doctor about your duloxetine if you are trying to get pregnant.

Pregnancy, post-natal and breastfeeding

Pregnancy

You should use good contraception when you are taking duloxetine. This is because we do not know for sure the effects of duloxetine on a developing baby (although when taken in usual doses there does not seem to be any link with malformations.

If you do become pregnant while you are on duloxetine, you should carry on taking the medicine and go back to your doctor as soon as possible, to see if you should stop or change your medicine.

Remember that you need to stay well through your pregnancy, and you may need a medicine to help you do that.

If you are planning a pregnancy, you should talk to your doctor about your options.

There may be a slight increase in the risk of miscarriage or premature birth.

If you and your doctor agree that you will carry on taking duloxetine, you should tell your midwife that you are taking it before you give birth.

Post-natal

If duloxetine is taken in the last five months of a pregnancy, it may cause a condition called persistent pulmonary hypertension of the new-born (PPHN). PPHN is linked more to SSRI antidepressants like citalopram and fluoxetine but it is included here because duloxetine has an overlap of drug action with SSRIs. PPHN can make the baby breathe faster and look a bit blue in colour. This happens in the first 24 hours after birth. You will need help from the midwife and doctors, so it is better if they are looking out for symptoms.

The newborn baby may also develop withdrawal effects that might include:

• irritability and crying a lot
• having difficulty sleeping or sucking

These might not happen straight away, so you should look out for them over the first few days after the baby is born. 

Breastfeeding

A small amount of duloxetine is passed to the baby in breastmilk. Breastfeeding can help with settling any withdrawal symptoms.

Talk to your doctor or midwife about your feeding options.

If your baby becomes restless, very sleepy or develops feeding problems, quickly seek help from your doctor.

Driving and transport

Taking duloxetine may affect your concentration, which could, in turn, affect your ability to do things like driving a car, riding a bike, using machines, or anything else that needs a lot of focus.

Duloxetine may also affect your eyesight and make you feel sleepy or dizzy.

It might be best to stop driving, riding a bike or operating machinery for the first few days, until you know how it affects you or until the effects pass.

Do not worry - most people drive as normal while taking duloxetine.

School and exams

Try not to take duloxetine for the first time just before your exams.

Taking duloxetine may affect your ability to do things that need a lot of focus, like exams.

Your eyesight may be affected, and you might have sleep problems or feel very sleepy during the day. You may also feel restless and find it hard to sit down and keep still.

You should talk to your doctor about any future exams if you are starting duloxetine.

You might decide together to delay starting it until you have done them. If they are more than a month away, however, you might find that it is better to start duloxetine to lift your mood and improve your motivation to study.

Do not worry - most people take exams as normal while taking duloxetine.

Friends and family

You may want to let your family and friends know you are taking duloxetine so they can support you and help you look out for side effects.

For guidance on this, check out our page on getting support with your medication.

Sport

Duloxetine is not a banned substance in sport.

Taking duloxetine may affect your ability to do things like riding a bike, competitive gymnastics, or anything else that needs a lot of focus. It can affect your eyesight, make you feel dizzy and sleepy, and make you feel restless and unable to sit still.

It might be best to stop such sports for the first few days, until you know how it affects you or the effects get better.

Do not worry - most people play sports as normal while taking duloxetine.

Alcohol, street drugs and smoking

Alcohol

You can continue to drink some alcohol while taking duloxetine.

Drinking alcohol every day, however, can make the symptoms of depression worse and you will not feel the benefit of your medicine.

During the first few days, it might be best to stop drinking alcohol until you see how the medicine affects you, or until the effects pass.

Street drugs

Be careful if you are also using street drugs.

Cannabis can make drowsiness, dizziness, confusion and difficulty worse when taken with duloxetine.

Cannabis and other drugs may have their own side effects on your mental health, like anxiety or psychosis. For more information, have a look at our drugs and alcohol page.

Methadone can make sleepiness worse with duloxetine. The duloxetine could increase the concentration of methadone in your body.

Duloxetine is likely to raise the effect of cocaine in your body, giving you a bigger reaction.

Taking duloxetine with cocaine or ecstasy or amphetamines could bring on serotonin syndrome. You could get a high temperature/fever, agitation, confusion, trembling or weird muscle movements. You need to go to hospital if this happens. Tell the doctor everything that you have taken.

Smoking

Cigarette smoke affects the amount of duloxetine in your body.

If you smoke, you will probably need a higher dose of duloxetine than someone who does not smoke.

Tell your doctor if you smoke, so that you get the right dose for you.

If you stop smoking, the level of duloxetine in the body rises, and you might need to reduce your dose of duloxetine slowly.

If you (re)start smoking, you will probably need to increase it again.

Go to your doctor for advice if you stop or start smoking.

It is the smoke, rather than nicotine, that has this effect so it should not be as much of a problem if you only vape.

Prescription medicines

Duloxetine does not mix well with some other medicines and drugs.

Do not take duloxetine if you take an antidepressant medicine called a monoamine oxidase inhibitor (MAOI), or if you have taken one in the last two weeks.

Always talk to the doctor if you are taking other medicines. Tell the pharmacist you are taking duloxetine if you buy medicines (including things you put on your skin) for common illnesses.

Other interactions

If you drink a lot of coffee, cola drinks or other caffeine drinks when taking duloxetine, it can put you at a higher risk of getting serotonin syndrome.

The symptoms are any combination of the following: high fever, agitation, confusion, trembling, sweating, diarrhoea (loose poo), fast heartbeat or weird movements of your muscles.

You need to go to a hospital straight away if you get these symptoms. 

Large doses of caffeine can bring on or worsen generalised anxiety and panic attacks, or bring on mania, so it may also make the underlying problem worse.

For all these reasons, it may be a good idea to limit caffeine while taking duloxetine.

References and further reading

For more helpful links and information, have a look at our references and further reading page.