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Mirtazapine (Remeron®/Remeron RD®)

Mirtazapine (Remeron® and generic forms) belongs to a group of medications called “antidepressants.”

What is this medication used for?

Mirtazapine is not approved by Health Canada for use in children and adolescents.

However, mirtazapine may help treat depression, depression associated with bipolar disorder, avoidant/restrictive food intake disorder (ARFID), and anxiety disorders like post-traumatic stress disorder (PTSD), panic disorder and social anxiety disorder (SAD).

When potential benefits outweigh risks, mirtazapine may be prescribed “off-label.” Learn more about off-label medication use:

Tell your doctor or pharmacist if you:

  • Have allergies or bad reactions to a medication.
  • Take (or plan to take) other prescription or non- prescription medications, including natural medicines. Some medications interact with mirtazapine. Your doctor may adjust medication doses or monitor for side effects.
  • Have a history (or family history) of heart, kidney or liver disease, bowel obstruction, diabetes or glaucoma
  • Miss a menstrual period, are pregnant, breast-feeding or planning a pregnancy
  • Use alcohol or street drugs. Taking mirtazapine together with certain substances may cause a bad reaction. Learn more at

When will the medication start to work?

You (or your family members) may notice improvements in sleep, appetite and energy within the first 2 weeks.

However, it may take 3 to 6 weeks before you begin to feel better. Full beneficial effects may take 4 to 8 weeks or longer.

Mirtazapine takes time to work. Continue taking mirtazapine as prescribed, even if you are feeling better. Talk with your doctor before you increase, decrease or stop taking mirtazapine.

This medication is not addictive. Do not stop taking it before talking to your doctor.

Possible common or serious side effects:

Side effects may be more common when starting a medication or after a dose increase. Talk to your doctor, nurse or pharmacist if any side effect concerns you.

  • Dizziness, drowsiness or headache
  • Headache, irritability or feelings of agitation
  • Abnormal dreams
  • Constipation, nausea or stomach ache
  • Increased appetite or weight gain
  • Dry mouth

Contact your doctor immediately if you experience:

  • Thoughts of hurting yourself, hostility or suicide
  • Change in mood to an unusual state of excitement, irritability or happiness
  • Seizures
  • Uncomfortable sense of inner restlessness or agitation
  • Skin rash, itchy skin or hives
  • Uncomfortable awareness of your own heartbeat, or sudden and brief loss of consciousness

How do I take this medication?

Mirtazapine is usually taken once daily, with or without food, preferably in the evening or at bedtime. Usually, you will start at a low dose and slowly increase this dose over several days to weeks, based on how you tolerate it.

Mirtazapine is available as regular tablets or as orally disintegrating tablets (Remeron RD®). Orally disintegrating tablets are very sensitive to moisture and should be handled with dry hands. They are packaged in “blister packs,” which should only be opened immediately before taking the tablet. The tablet should be placed on your tongue and will disintegrate quickly. It can be swallowed with or without water, but should not be chewed.

What precautions should my doctor and I be aware of when taking this medication?

  • While taking mirtazapine, if you feel dizzy, drowsy or slowed down, do not drive a car or operate heavy machinery. Alcohol could make this worse. Try to avoid alcohol while taking mirtazapine.
  • Mirtazapine and medications like it are associated with a rare side effect called “serotonin syndrome,” especially when used in combination with other serotonergic drugs such as amphetamines and most other antidepressants. Symptoms include diarrhea, sweating, increased heart rate, tremors, severe muscle stiffness and increased agitation.
  • Do not to stop taking mirtazapine suddenly. Stopping abruptly is associated with “antidepressant discontinuation syndrome.” This involves flu-like symptoms, trouble sleeping, nausea, irritability, headache and abnormal sensations that feel like electric shocks, burning, tingling or numbness. If stopping or changing medications, your dose should be reduced slowly.

What special instructions should I follow while using this medication?

  • Keep all appointments with your doctor and the lab.
  • Your doctor may want to talk to you within 1-2 weeks of starting mirtazapine, and meet with you over time to make sure it is working well for you and check for side effects.
  • Do not allow anyone else to use your medication.

What should I do if I forget to take a dose of this medication?

If you take mirtazapine only at bedtime and forget to take a dose, skip the missed dose and continue regularly with your next scheduled dose.

If you take mirtazapine more than once a day and forget to take a dose of mirtazapine, take the missed dose as soon as you remember. However, if it is within 4 hours of your next schedule dose, skip the missed dose and continue with your regular schedule. DO NOT double your next dose to try to ‘catch up’.

How do I store this medication?

Keep this medication in the original container, stored at room temperature away from moisture and heat and protected from light. Keep this medication out of reach and sight of children.

How does this medication work?

Mirtazapine increases levels of the brain chemicals norepinephrine and serotonin. These brain chemicals do not function properly in people who have depression or anxiety. The exact way that mirtazapine improves symptoms of depression and anxiety disorders is not known. Mirtazapine improves symptoms of insomnia by blocking the actions of other brain chemicals, histamine and acetylcholine.

How well does the medication work in children and adolescents?

Mirtazapine has not been well studied in children and adolescents. Generally, it has been shown to be no better than placebo (an inactive pill) for treatment of depression in children and adolescents. However, mirtazapine may be used to treat other disorders like insomnia, anxiety disorders and ARFID. Mirtazapine is sometimes prescribed for treatment of children and adolescents with depression or anxiety when other treatments have not been effective. Whenever possible, the addition of talk therapy such as Cognitive Behavioural Therapy (CBT) may help increase the potential for benefit.

How long should I take the medication for?

This depends on the symptoms you have, how frequently they occur and how long you have had them. Most people need to take mirtazapine for at least 6 months. This allows time for symptoms to stabilize and function to improve. After this time, you and your doctor can discuss the benefits and risks of continuing treatment.

If you have had several episodes of severe depression and you tolerate mirtazapine well, you may be asked to take mirtazapine on an ongoing basis. Continuing treatment will significantly decrease the chance that you may have another episode of depression.

Do not increase, decrease or stop taking mirtazapine without discussing it with your doctor, even if you are feeling better. If you stop taking mirtazapine suddenly, it is possible that your symptoms may return or you may have a bad reaction.

TIP: Use the Kelty Mental Health Antidepressant Monitoring Form for Children and Adolescents to
help measure your progress on this medication.

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