Sounds like 'mer-TAZ-uh-peen'

Key points about mirtazapine

  • Mirtazapine is used to treat moderate to severe depression.
  • Mirtazapine is also called Mirtazapine(Noumed)®, Apo-Mirtazapine®, Zispin®.
  • Find out how to take it safely and possible side effects.
blue unaunahi tile generic
Print this page

Mirtazapine is used to treat moderate to severe depression. It is believed that mirtazapine works by increasing the activity of certain chemicals working in our brains called neurotransmitters. These pass signals from one brain cell to another. Although we don’t know for certain, the neurotransmitters that are most likely to be involved in depression are thought to be serotonin and noradrenaline. Read more about antidepressants.

In New Zealand mirtazapine is available as 30 milligram and 45 milligram tablets.

If you need help or want to talk to somebody about your mental health, you can get support from any of the following:

  • Free call or text 1737 any time for support from a trained counsellor
  • Lifeline 0800 543 354 (0800 LIFELINE) or free text 4357 (HELP)
  • Suicide Crisis Helpline 0508 828 865 (0508 TAUTOKO)
  • Healthline 0800 611 116
  • Samaritans 0800 726 666.

  • The usual dose of mirtazapine is 30 milligrams once a day.
  • Some people may need higher doses.
  • Your doctor will start you on a low dose and if you need to, will increase your dose slowly. This allows your body to get used to the medicine and reduces side effects.
  • Always take your mirtazapine exactly as your doctor has told you. The pharmacy label on your medicine will tell you how much to take, how often to take it, and any special instructions.

  • Mirtazapine is usually taken once a day, at night, before going to bed. Take mirtazapine at the same time each day.
  • Swallow the tablet with a glass of water. Do not chew it. 
  • You can take mirtazapine with or without food.
  • If you forget to take your dose, just take the next dose at the right time. Do not take double the dose.
  • Keep taking mirtazapine every day. It may take a few weeks before you notice the full benefits of mirtazapine
  • If you think mirtazapine is not working for you, do not stop taking it suddenly; speak to your doctor or nurse before stopping. It is usually best to stop taking mirtazapine very slowly over a few weeks to avoid side effects.

Here are some things to know when you're taking mirtazapine. Other things may be important as well, so ask your healthcare provider what you should know about.

  • Alcohol: avoid alcohol while you are taking mirtazapine, especially when you first start treatment. Drinking alcohol while taking mirtazapine can cause drowsiness and affect concentration, putting you at risk of falls and other accidents. It can also cause agitation, aggression and forgetfulness. If you do drink alcohol, drink only small amounts and see how you feel. Do not stop taking your medication.
  • Other medicines: Mirtazapine interacts with a number of medications, herbal supplements (such as St. John's Wort) and rongoā Māori, so check with your doctor or pharmacist before starting mirtazapine or before starting any new medicines, especially pain relief medicines and other medicines that can cause drowsiness.
  • If you have a fever, sore throat or sore mouth while taking mirtazapine, let your doctor know immediately.

Like all medicines, mirtazapine can cause side effects, although not everyone gets them. Often side effects improve as your body gets used to the new medicine.

Suicidal behaviour

The use of antidepressants has been linked with self-harm or suicidal thoughts and behaviour. Children, teenagers, young adults and people with a history of suicidal behaviour are most at risk. This is most likely during the first few weeks of starting treatment or if the dose is changed. It is important to look out for signs of suicidal behaviour such as suicidal thoughts, self-harm, worsening of low mood, agitation or aggression. If you notice any of these signs, contact your doctor immediately.

If you need urgent help or are concerned, phone:

  • Lifeline 0800 543 354 (available 24/7), or
  • Healthline 0800 611 116, who can give you the phone number for your local mental health crisis line.

Other side effects

Side effects What should I do?
  • Feeling sleepy, drowsy, dizzy or tired
  • Be careful when driving or using tools until you know how this medicine affects you
  • Do not drink alcohol
  • Take your medicine at night rather than in the morning
  • Tell your doctor if troublesome
  • Increased appetite
  • Weight gain
  • These are quite common 
  • It may be helpful to make changes to your diet and usual exercise.
  • Tell your doctor 
  • Dry mouth, feeling faint, trouble sleeping, constipation
  • Tell your doctor
  • Suicidal thoughts, thoughts of harming yourself, or worsening depression
  • Tell your doctor immediately or ring HealthLine 0800 611 116
  • Fever, sore throat, sores in the mouth, feeling tired and unwell especially in the first 4-6 weeks of starting mirtazapine
  • Tell your doctor immediately or ring HealthLine 0800 611 116
  • Signs of serotonin syndrome such as feeling agitated and restless, heavy sweating, shivering, fast heart rate or irregular heartbeat, headache, diarrhoea and rigid or twitching muscles 
  • You are at increased risk of serotonin syndrome if you have just started taking mirtazapine or recently increased the dose, or if you are taking other medicines that interact with mirtazapine
  • Tell your doctor immediately or ring HealthLine 0800 611 116
Did you know that you can report a side effect to a medicine to CARM (Centre for Adverse Reactions Monitoring)? Report a side effect to a product(external link)

The following links provide further information on mirtazapine.

Medsafe Consumer Information Sheets: Avanza(external link)


5 questions to ask about your medications(external link) Health Quality and Safety Commission, NZ, 2019 English(external link), te reo Māori(external link)


  1. Mirtazapine(external link) New Zealand Formulary
  2. The role of medicines in the management of depression in primary care(external link) BPAC 2017

Free helplines

Healthline logo

Text 1737 Helpline logo

Logo with link to Māori Pharmacists website

Credits: Sandra Ponen, Pharmacist, Healthify He Puna Waiora. Healthify is brought to you by Health Navigator Charitable Trust.

Reviewed by: Angela Lambie, Pharmacist, Auckland

Last reviewed:

Page last updated: