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Key facts

  • Mirtazapine is an antidepressant medicine.
  • Medical experts believe mirtazapine works by balancing chemicals in the brain (such as serotonin and noradrenaline) that are thought to affect mood and emotions.
  • Common side effects of mirtazapine include drowsiness, increased appetite and weight gain.
  • There are many alternatives to mirtazapine including other antidepressant medicines, lifestyles changes and psychological therapies.
  • Discuss with your doctor the best strategy for managing your depression.

Looking for a medicine?

Visit healthdirect’s list of medicines that contain mirtazapine to find out more about a specific medicine.

What is mirtazapine?

Mirtazapine is an antidepressant medicine.

What is mirtazapine used for?

Mirtazapine is mainly used to treat depression and/or to prevent it from occurring again.

Your doctor might prescribe mirtazapine for another reason. If you are unsure why you have been prescribed mirtazapine, ask your doctor.

How does mirtazapine work?

Medical experts believe mirtazapine works by balancing chemicals in the brain that are thought to affect mood and emotions. The chemicals involved are serotonin and noradrenaline.

What forms of mirtazapine are available?

Mirtazapine is the name of the active ingredient. It is available in many different brands, which have different:

  • names
  • appearances (size, shape or colour)
  • forms (tablets and disintegrating tablets)
  • packaging

No matter which brand you are prescribed, mirtazapine works in the same way to treat depression.

In Australia, mirtazapine is only available with a doctor's prescription.

What are the possible side effects of mirtazapine?

Common side effects of mirtazapine include:

  • drowsiness and tiredness
  • increased appetite and weight gain
  • fluid retention and swelling
  • weakness

Tell your doctor if you have rare but serious side effects of mirtazapine, which include:

  • itching or a skin rash
  • feeling extremely restless and an overwhelming urge to always be moving
  • unusual changes in behaviour
  • suicidal thoughts

If you, or someone else, is at immediate risk of suicide, call triple zero (000) and ask for an ambulance.

Each person responds to medicines differently. Just because a side effect is listed does not mean you will experience it. Even if you experience a side effect, you and your doctor will need to weigh up the medicine's benefits against its risks before deciding what to do. This could be deciding to make no changes, change the dose or switch to another treatment option.

If you experience a serious or life-threatening side effect, call triple zero (000) and ask for an ambulance.

This is not a full list of side effects for mirtazapine. For more information on the side effects and risks, read the Consumer Medicine Information (CMI) for the brand of mirtazapine you are taking, or talk to your doctor or pharmacist.

What should I be careful of when taking mirtazapine?

Mirtazapine can make the effects of alcohol and sedative medicines such as benzodiazepines stronger. Avoid alcohol when taking mirtazapine and speak to your doctor if you have also been prescribed a benzodiazepine medicine, such as diazepam.

If you are planning to stop taking mirtazapine, talk to your doctor. It is important not to stop mirtazapine suddenly, as this may cause symptoms such as nausea, headache, dizziness and anxiety.

When should I speak to my doctor?

Speak to your doctor if you:

  • feel that taking the medicine has not helped reduce your symptoms of depression
  • experience side effects that trouble you
  • have signs of an allergic reaction
  • have a health condition or are taking medication that may affect how your body reacts to mirtazapine
  • become pregnant or start breastfeeding

Read the CMI in the package for full details about when to speak with your doctor before or after you have started taking mirtazapine.

ASK YOUR DOCTOR — Preparing for an appointment? Use the Question Builder for general tips on what to ask your GP or specialist.

Are there alternatives to mirtazapine?

Your doctor might prescribe another type of antidepressant medicine or suggest that you try psychological therapy, such as cognitive behaviour therapy (CBT).

There might be other approaches that can help, such as getting regular exercise and looking for pleasurable things to do each day. You can undertake CBT and other psychological treatments in combination with antidepressant medicine.

Resources and support

Asking about your treatment or medication is important to help you understand your options. Read our guide to important questions to ask your pharmacist or doctor before taking a medicine.

You can also visit healthdirect's list of medicines that contain mirtazapine to read the CMI for the brand of mirtazapine prescribed.

Learn more here about the development and quality assurance of healthdirect content.

Last reviewed: April 2023

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