How it works
What does duloxetine do?
Duloxetine is a serotonin and 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 and 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 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
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:
- tingling feelings like pins and needles, or electric shocks (particularly in the head and down the back)
- sleep disturbances (vivid dreams, nightmares, not being able to sleep)
- feeling anxious, restless, agitated or irritable
- feeling sick or being sick
- 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 March 2020.