Medication Information Leaflet

What is this medication for?

Mirtazapine belongs to a class of medications known as Noradrenergic, Specific Serotonergic Antidepressants (NaSSA). It is used to treat symptoms of depression (low mood) such as:

  • Feeling sad
  • Feeling hopeless or useless
  • Feeling bad about yourself
  • Thoughts of ending your life
  • Poor sleep, energy or appetite

Mirtazapine may also be used for other conditions. Check with your healthcare professional if you are unsure why you are given this medication. 

How should I take/use this medication?

  • Mirtazapine may be taken with or without food.
  • Mirtazapine is available as orodispersible tablets. This means that these tablets dissolve when you put them in your mouth and can be swallowed without water.
  • To remove the orodispersible tablets from the blister strip:
    1. Dry your hands. The tablets will dissolve if your hands are wet.
    2. Follow the dotted lines on the strip and cut out a square containing a tablet
    3. On the back of the square, there are black arrows printed on certain corners. Carefully peel off the foil, starting from the corner indicated by the black arrow.
    4. Place the tablet on your tongue. You may take it with or without water. Take the tablet as soon as possible once the foil has been peeled open.
  • Take your medication according to the instructions stated on the medication label.
  • Do not stop taking or adjust the dose of this medication without checking with your doctor.
  • Mirtazapine needs to be taken regularly for a few weeks before you can feel its full benefits. You should not stop taking this medication even if you do not feel better at the beginning. Continue to take this medication even after you feel better to prevent your symptoms from returning.
  • Do check with your doctor on how long you will have to be on this medication.
  • You may experience unpleasant effects such as dizziness, headache, difficulty sleeping, irritability, and nausea if you suddenly stop taking the medication on your own.

What should I do if I forget to take/use this medication?

  • If you forget to take a dose, take it as soon as you remember. However, if more than half of the time to the next dose has passed, skip the missed dose and take the next dose at your usual timing.
  • For example, for a medication to be taken two times daily at 8am and 8pm, and you missed your first dose at 8am, skip the first dose if it is after 2pm, and take your second dose at the usual timing at 8pm. Do not take two doses to make up for the missed dose.

What precautions should I take?

Inform your healthcare professional if: 

  • You are allergic to this medication or any of the other ingredients of this medication
  • You are pregnant, planning to become pregnant, or breastfeeding. If you are pregnant or breastfeeding, your doctor would have discussed the potential benefits and side-effects with you and should you have further questions or concerns, do consult your doctor.
  • You are taking any other medications (including those that can be bought without a prescription), supplements such as St John’s Wort, traditional Chinese medicine and herbal products. Some of them may affect how this medication works or cause serious drug interactions.
  • You are unable to take artificial sweeteners. Mirtazapine orodispersible tablets contain aspartame, a type of artificial sweetener.
  • You have or have ever had:
    • Other drug allergies
    • An increase in the level of phenylalanine in the blood (also known as phenylketonuria, a genetic disorder)
    • Heart, kidney or liver disease
    • Medical conditions such as seizures (fits), Parkinson’s disease, urinary problems, diabetes, high cholesterol, low blood pressure
    • Other mental health conditions such as bipolar disorder, abnormally high or excited mood (mania)
    • Been taking other medications for low mood in the past 2 weeks

What are some common side-effects of this medication?

The mentioned side effects generally affect up to 10% of patients.

  • Drowsiness or feeling tired
    • Avoid driving or taking part in activities that require concentration
    • Discuss with your doctor if you can take your medication at a different time of the day
  • Increase in appetite, weight gain
    • Monitor your weight, exercise regularly and eat a healthy, balanced diet
  • Dry mouth
    • Chew sugar-free gum, suck on sugar-free hard candies or ice chips, and sip water regularly
  • Constipation
    • Drink more water (if you do not have any fluid restriction), eat more high-fibre foods, and exercise regularly
    • Speak to your doctor or pharmacist if you need medication to help with your constipation
  • Dizziness
    • Get up slowly from sitting or lying down position
  • Headache
    • Speak with your doctor if it affects your daily life

Most of the side effects listed here will improve with time. Speak with your doctor or pharmacist if they continue, get worse or are affecting your daily life. 

What are some rare but serious side-effects that I need to seek medical advice immediately?

The symptoms of a drug allergy include one or more of the following:   

  • Swollen face/eyes/lips/tongue
  • Difficulty in breathing
  • Itchy skin rashes over your whole body

Rarely this medication may cause:

  • Swelling of hands, ankles or feet (edema)
  • Flu-like symptoms (fever, chills, sore throat), mouth sores/ulcers (signs of infection due to bone marrow suppression)
  • Loss of appetite, severe nausea or vomiting, pain in the upper part of the stomach, yellowing of the skin or ‘whites’ of the eyes, dark-brown coloured urine and/or pale/clay-coloured stools (signs and symptoms of liver problem)
  • Unexplained fever, confusion, fast heartbeat, severe weakness, uncontrolled movements or twitching of the muscles (signs and symptoms of serotonin syndrome)
  • Feelings of irritability, intense agitation or anxiety, restlessness
  • Unusual thoughts, talking, feeling, and acting with excitement that you cannot control (signs and symptoms of mania)
  • Feeling confused, muscle weakness/cramps, difficulty in concentrating or remembering things, feeling unsteady when walking (signs and symptoms of low sodium in the blood)
  • Seizures (fits)

If you experience any of these symptoms, you should stop your medication and see your healthcare professional immediately.


In some cases, particularly in young people below the age of 25 years, this medication may cause the following changes to a person’s mental condition, especially in the first few weeks of treatment or during dose changes:

  • New or worsening thoughts of harming yourself or ending your life
  • Worsening agitation, restlessness, violent behaviour, or
  • Other changes in mood or behaviour

Please inform your doctor as soon as possible, or for your family or caregiver to inform your doctor if you are unable to seek treatment on your own.

Do not stop taking this medication on your own without discussing with your doctor.

It is important to note that your doctor has prescribed this medication as he/ she feels you will benefit more from taking this medication over the possible risks that it may cause, which have a low chance of occurring, and most people take this medication without any of such problems.

What food or medication should I avoid when I take this medication?

Avoid drinking alcohol while taking Mirtazapine as it can worsen the symptoms of your depression and cause excessive sleepiness.

How should I store this medication?

Store in a cool and dry place, away from direct sunlight. Keep this medication away from children. Avoid keeping the medication in the fridge as the tablets will absorb moisture and break down on its own.

How should I throw away this medication safely?

Pack this medication into a trash bag and seal it tightly before throwing into the rubbish chute or bin.


Please take note that the above is not a complete list of all possible side effects. If you have any concerns about your medication or if you have other side effects that you think are caused by this medication, please consult your doctor or pharmacist.

If you take more than the recommended dose, please seek medical advice immediately. The information provided on this page does not replace information from your healthcare professional. Please consult your healthcare professional for more information.

This article is jointly developed by members of the National Medication Information workgroup. The workgroup consists of cluster partners (National Healthcare Group, National University Health System and SingHealth), community pharmacies (Guardian, Unity and Watsons) and Pharmaceutical Society of Singapore. The content does not reflect drug availability and supply information in pharmacies and healthcare institutions. You are advised to check with the respective institutions for such information.

Last updated on Aug 2022

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