Duloxetine

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.

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

In studies, 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.

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.

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.

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 and confusion 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 amfetamines 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.

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. MAOIs include drugs such as moclobemide, isocarboxazid, phenelzine and tranylcypromine.

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.

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
• 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.

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.

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 but go back to your doctor as soon as possible to discuss whether 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 breast milk. 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.

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 positive 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.

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.

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.