Mirtazapine ("mir-TAZ-a-peen") is an antidepressant mainly used to treat depression

This page will give you general information about mirtazapine. It is not medical advice. Always talk to your doctor about your situation and whether this medication is for you.

What's it for?

Mirtazapine is licensed to treat the following conditions:

Taking sertraline, diazepam and mirtazapine: Clare's story

Clare shares how taking mirtazapine helped her with her depression and anxiety.

Read Clare's story

Name: mirtazapine ("mir-TAZ-a-peen")

Other names: Zispin ("ZISS-pin")

Medication type: antidepressant

What can it be used for?
If you are 18 or over, the doctor can prescribe mirtazapine for you as a licensed medicine for depression.

There is less research about its use and effectiveness in people aged under 18. Even so, specialists might prescribe it ‘off-label’ if they believe it is the best medicine for you

Ways to take it:

Tablets: 15mg, 30mg and 45mg strengths

Oral dispersible tablets: 15mg, 30mg and 45mg strengths

Liquid: 15mg in 1ml

How it works

What does mirtazapine do?

Mirtazapine is an antidepressant, which works by adjusting the levels of chemicals in your brain.

The brain has many naturally occurring chemical messengers (or "neurotransmitters"). Two of these - serotonin (sometimes called 5-HT) and noradrenaline - are important in the areas of the brain that control mood and thinking.

It is known that these chemical messengers are not as effective or active as usual in the brain when someone is feeling depressed. Mirtazapine increases the amount of these chemical messengers in the brain, which can help to improve mood.

How long does mirtazapine take to start working?

Antidepressants like mirtazapine can start to work on depression within the first two weeks of treatment, and the improvement continues over the following few weeks. It may take four weeks or a little longer for you to get the full effect.

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

How long will I need to take mirtazapine?

Keep taking mirtazapine as you get better, which can take a few months, and then continue taking it for another six to 12 months after that as advised by your doctor.

If your illness has come back, then you should keep taking mirtazapine for at least two years after getting better. This will help keep you well.

If you stop taking the mirtazapine too soon, there is more chance that your symptoms will come back.

Discuss with your doctor how long you should take mirtazapine before starting your treatment.

If you want to stop mirtazapine, speak to your doctor to make sure it is not too soon.

Your doctor needs to know if...

You need to talk to your doctor or pharmacist before starting treatment with mirtazapine if you have experienced any of the following:

  • seizures (fits)
  • liver disease, including jaundice
  • kidney disease
  • heart disease, or low blood pressure
  • schizophrenia
  • bipolar disorder
  • diabetes
  • eye disease, such as glaucoma (increased pressure in the eye)
  • difficulty urinating (weeing), which might be caused by an enlarged prostate

If you have ever tried to harm yourself or take your own life, or thought about harming yourself or taking your own life, you should tell your doctor, as these thoughts might come back early on in treatment.

The mirtazapine tablets that you swallow may not be suitable for you if you have problems eating some sugars or dairy (milk-based) foods, as they contain lactose.

The mirtazapine orodispersible (‘melt in your mouth’) tablets contain aspartame, which can be a problem for people who have a condition called phenylketonuria.

The oral solution contains a small amount of alcohol. It also contains maltitol, which can be a problem for anyone who has an intolerance to a sugar called fructose.

Mirtazapine medicines do not contain any animal products.

Taking mirtazapine

You should only take mirtazapine as agreed with your doctor

You will get the best effect from mirtazapine 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.

Mirtazapine is taken once a day. It is best to take it at bedtime because it can make you feel sleepy.

You can take your medicine before or after food.

For the plain tablets, swallow them whole with a drink of water or juice - if you chew them, they taste bitter. The plain tablets should also be swallowed whole with at least half a glass of water while you are sitting up or standing up. This is to make sure that they reach the stomach and do not stick in your throat.

For the orodispersible tablets (melts), peel off the cover from the blister pack rather than pushing the tablet through, so it does not break, then put the tablet on your tongue and let it dissolve there.

There may be a measuring syringe to use with the oral solution to help you get the dose right. Read the instructions before you use it.

You can add your dose of the oral solution to a glass of water.

What if I miss a dose?

If you forget your bedtime dose of mirtazapine and you remember in the morning, then it is probably best that you miss that dose. This is because mirtazapine can make you sleepy, so it is best not to take it in the daytime. Just take your next dose at bedtime as usual.

Do not take a double dose to try to catch up because this could cause you to have extra side effects.

What will happen if I forget to take my mirtazapine?

Mirtazapine works best if you do not miss any doses. However, if you are not missing more than one dose each week, it is unlikely that there will be any problems.

If you forget to take your tablets for a few days, you may start getting your old symptoms back, or you may get withdrawal symptoms such as headache, dizziness, anxiety, or feeling sick. You should talk to your doctor about this.

Stopping the use of mirtazapine

Stopping this medicine quickly, or reducing the dose too much at once, may cause your old symptoms to come back. It may also give you unpleasant withdrawal symptoms including dizziness, agitation, anxiety, headaches and feeling or being sick. These are usually mild and go away after a few days.

Once you start taking mirtazapine, the brain adjusts to having a new level of noradrenaline and serotonin around. Withdrawal symptoms are not caused by the medication being addictive, it’s just your brain readjusting to a change in the balance of chemicals.

It is better to agree stopping with a doctor who will reduce your dose gradually over a few weeks.

The information on this page was reviewed by the College of Mental Health Pharmacy in March 2020.

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