Naomi Carr
Author: Naomi Carr Medical Reviewer: Dr. Leila Khurshid Last updated:

Mirtazapine, also known as Remeron, is a tetracyclic antidepressant, primarily used to treat major depressive disorder in adults. Take this medication exactly as prescribed and discuss with your doctor before starting any other medication (prescribed or over the counter) while on mirtazapine, as adverse effects can occur.

Mirtazapine brand names

  • Remeron
  • Remeron SolTab

What is mirtazapine prescribed for?

Mirtazapine is used to treat major depressive disorder. It is not FDA approved for the use in children under the age of 18, as the safety and effectiveness of this is not clear. It can be prescribed to this age group off-label, if it is deemed necessary [1][2].

Mirtazapine helps to alleviate various symptoms of major depression, including low mood, trouble sleeping, and poor appetite.

This medication may also be prescribed off-label for the treatment of other mental health conditions and mood disorders, including insomnia, anxiety disorders, post-traumatic stress disorder (PTSD), and obsessive-compulsive disorder (OCD).

How does mirtazapine work?

Mirtazapine works by affecting certain areas of the brain, to result in an increase in the neurotransmitters serotonin and norepinephrine. This then helps to boost the mood and relieves various symptoms of depression. It also has a slight sedative effect, which is how it can also improve sleep [3][4].

How is mirtazapine usually taken?

Mirtazapine is available as an oral tablet, in 7.5mg, 15mg, 30mg, and 45mg strengths, and as an orally disintegrating tablet, in 15mg, 30mg, and 45mg strengths.

Typically, you will only be prescribed one dose of mirtazapine per day, which should be taken before you go to bed, as the medication can have a sedative effect.

If you are prescribed the tablet form of this medication, you should swallow it whole with water. Do not break or crush this tablet.

If you are prescribed the orally disintegrating form of this medication, you should place the tablet on your tongue, allowing it to dissolve, and then swallow the remaining substance. Do not break or split this tablet.

Your doctor will likely start you on a low dose, around 15mg, to be taken once per day.

Your dose may then gradually increase over the following weeks, until the most effective dose has been reached. This will likely not increase above 45mg per day [4].

Your doctor will monitor any side effects or changes in your symptoms. This monitoring is usually more regular at the beginning of your treatment and may reduce as your symptoms and condition stabilize.

This medication should be taken as prescribed, without missing a dose. If a dose is missed, take the medication as soon as possible, or if it is close to the next dosage time, skip the missed dose. Never take double your prescribed dose in one go, as this can have adverse effects and may increase the risk of side effects.

How long does mirtazapine stay in your system?

After you start taking mirtazapine, you may notice some improvements in your symptoms within the first week or two, but it may take 2-3 months for the medication to take full effect [5].

After you stop taking mirtazapine, the effects of the medication may subside after a few days, although it may take several weeks for it to completely leave your body.

Do not suddenly stop taking mirtazapine without medical advice, even if you feel better, as this can have serious impacts on your physical and mental health and cause an increase in symptoms of depression. If your doctor advises that it is safe to come off this medication, they will likely reduce your prescription slowly, to prevent adverse effects.

Mirtazapine side effects

When you begin a new medication, you may experience some common side effects. These will likely reduce naturally over the first few weeks of treatment, but if they continue or become problematic, consult your doctor immediately, as you may need to change your dose or medication.

Common side effects include:

  • Drowsiness or dizziness
  • Increase in appetite and weightgain
  • Stomach upset, such as constipation, diarrhea, nausea, or vomiting
  • Dry mouth

Serious side effects of mirtazapine are less common, but if you do experience any of the following, they may be a sign of an allergic reaction, infection, low white blood cell count, serotonin syndrome, or glaucoma, so you should get medical attention immediately [1][5]:

  • Changes in vision
  • Redness, swelling, or pain in or around the eyes
  • Chest pain
  • Low blood pressure
  • Increased heart rate
  • Fever
  • Shivering or shaking
  • Loss of coordination
  • Seizures
  • Muscle pain
  • Changes in mental state, such as an increase in depression or anxiety, agitation, aggression or violence, hallucinations, delusions, abnormal dreams, or trouble sleeping

Mirtazapine precautions

Mirtazapine can cause an increase in suicidal ideation, particularly when first starting your treatment. This risk has been found to be higher for people under 24 years old [1][2]. If you begin thinking of harming or killing yourself, or notice an increase in any other mental health symptoms, consult with your doctor or mental health professional immediately.

It is important that your doctor is aware of any past or present mental health conditions you have experienced, to enable safe monitoring of your condition while on this medication, or to decide if it is safe for you.

Discuss with your doctor all your past and present physical health conditions, as they may impact your ability to take this medication safely.

You may not be able to take this medication safely if you have experienced heart, liver, or kidney problems, because of the potential side effects. Your doctor may wish to closely monitor your physical changes during your treatment.

Tell your doctor about all medications you are currently taking, or plan to take (including vitamins and dietary supplements), as they may cause adverse reactions.

Discuss with your doctor if you are pregnant or planning to get pregnant. It is important that you are aware of any risks and can make an informed decision about your treatment. Your doctor may deem it necessary to start, or continue, your mirtazapine prescription while pregnant.

Discuss with your doctor if you are breastfeeding, as you may still be able to take mirtazapine, but the medication may be passed to your baby in small amounts through breast milk [4][5], so you should be aware of the risks and proceed with caution, monitoring any mental or physical changes in your baby.

This medication can cause drowsiness and sedation, so it is important to avoid driving until you are aware of how mirtazapine affects you and it is safe to do so.

Mirtazapine interactions

Certain antidepressant drugs, called monoamine oxidate inhibitors (MAOIs), should not be taken with mirtazapine, due to the increased risk of serotonin syndrome. There should be a space of 14 days between your last MAOI dose and your first mirtazapine dose [1][2].

Other medications and substances can interact with mirtazapine, causing a decrease in effectiveness or increase in side effects and risks. This includes St. John’s wort, opiates, benzodiazepines, seizure medication, migraine medication, some antidepressants and antipsychotics, antifungal medications, blood thinners, and sedatives and tranquilizers. Inform your doctor of your current medications.

Avoid or limit alcohol use while taking mirtazapine, as it can increase the sedative effects and may contribute to a clinical worsening of symptoms.

Mirtazapine storage

Always keep all medications out of reach of children.

Store mirtazapine in its original packaging, in airtight containers, and at room temperature (never above 86 F).

If you need to dispose of medication that is out of date or no longer needed, contact a medical professional to ensure it is disposed of appropriately. Never flush medications down the toilet or put them in the trash, as this can create unnecessary risks.

What to do if you overdose on mirtazapine

If you overdose on mirtazapine, call a medical professional, or Poison Control on 1-800-222-1222, or in case of an emergency, call 911. Symptoms of a mirtazapine overdose include drowsiness, confusion, respiratory depression or breathing difficulties, and seizures [1].

Frequently asked questions about mirtazapine

Is mirtazapine addictive?

Mirtazapine is not considered an addictive substance [10]. However, with extended use, you may develop a physical dependency on the medication, which can cause withdrawal effects when the medication is stopped [1][6]. Your doctor will likely reduce your prescription slowly, rather than stopping suddenly, to prevent withdrawal symptoms.

Withdrawal symptoms can increase the chance of mirtazapine misuse, as a way of preventing these symptoms. Take your prescription exactly as prescribed by your doctor to prevent this.

Mirtazapine has been found to cause a quicker boost in mood than many other antidepressants [6][7], so is sometimes misused to create this effect.

Never share your medication with others, even if you think it may help. This can be harmful and may increase the risk of medication misuse.

Mirtazapine vs. fluoxetine: What’s the difference?

Mirtazapine and fluoxetine are both antidepressant medications. However, mirtazapine is classified as a tetracyclic antidepressant and fluoxetine a selective serotonin reuptake inhibitor (SSRI), so they work in slightly different ways.

They have been found to be fairly equal in their effectiveness in treating depression, but mirtazapine usually causes a quicker improvement in symptoms [7][8][11].

Mirtazapine tends to cause a sedative effect, while fluoxetine can help to make you more active. If you have trouble sleeping, mirtazapine may be better suited, while fluoxetine can be preferrable for those who feel lethargy or anhedonia (tired or lacking interest in things) [9].

Mirtazapine can cause an increase in appetite or weight, so can be useful for those who have experienced a loss in appetite due to their condition or have a history of anorexia. Fluoxetine has not been found to cause a noticeable increase in weight or appetite [9].

There are various types of antidepressant medication, so you may wish to discuss alternatives with your doctor, who can advise you of the varying side effects and help you find the medication that works best for you. You may also wish to utilize talking therapies alongside your medication, to receive the most effective treatment [5].

  1. Remeron (Mirtazapine).(2011, November). Access Data FDA. Retrieved from https://www.accessdata.fda.gov/drugsatfda_docs/label/2021/020415s038,021208s028lbl.pdf
  2. Mirtazapine: MedlinePlus Drug Information.(n.d.). MedlinePlus. Retrieved from https://medlineplus.gov/druginfo/meds/a697009.html
  3. Anttila, S.A., & Leinonen, E.V. (2006). A Review of the Pharmacological and Clinical Profile of Mirtazapine. CNS Drug Reviews, 7(3), 249–264. https://doi.org/10.1111/j.1527-3458.2001.tb00198.x
  4. Jilani, T.N., Gibbons, J.R., Faizy, R.M., & Saadabadi, A. Mirtazapine. [Updated 2022 Sep 7]. In StatPearls [Internet]. Treasure Island, FL: StatPearls Publishing; 2022 Jan-. Available from https://www.ncbi.nlm.nih.gov/books/NBK519059/
  5. Mirtazapine (Remeron).(n.d.). National Alliance on Mental Illness (NAMI). Retrieved November 2, 2022, from https://www.nami.org/About-Mental-Illness/Treatments/Mental-Health-Medications/Types-of-Medication/Mirtazapine-(Remeron)
  6. Graves, S. M., Rafeyan, R., Watts, J., & Napier, T. C. (2012). Mirtazapine, and mirtazapine-like compounds as possible pharmacotherapy for substance abuse disorders: Evidence from the bench and the bedside. Pharmacology & Therapeutics, 136(3), 343–353. https://doi.org/10.1016/j.pharmthera.2012.08.013
  7. Holm, K.J., Jarvis, B., & Foster, R.H. (2000). Mirtazapine.PharmacoEconomics, 17(5), 515–534. https://doi.org/10.2165/00019053-200017050-00008
  8. Versiani, M., Moreno, R., Ramakers-van Moorsel, C.J.A., & Schutte, A.J. (2005). Comparison of the Effects of Mirtazapine and Fluoxetine in Severely Depressed Patients. CNS Drugs19(2), 137–146. https://doi.org/10.2165/00023210-200519020-00004
  9. Comparing Fluoxetine vs Mirtazapine. (n.d). Drugs.com. RetrievedNovember 2, 2022,from https://www.drugs.com/compare/fluoxetine-vs-mirtazapine
  10. Information on the Use of Mirtazapine in Young People. (2021, February). NHS Sussex Partnership. https://www.sussexpartnership.nhs.uk/sites/default/files/documents/mirtazapine_-_patient_and_parent_information_for_under_18s_-_feb_21_0.pdf
  11. Fluoxetine vs Mirtazapine Comparison. (n.d.). Drugs.com. Retrieved April 24, 2023, from https://www.drugs.com/compare/fluoxetine-vs-mirtazapine
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Naomi Carr
Author Naomi Carr Writer

Naomi Carr is a writer with a background in English Literature from Oxford Brookes University.

Published: Nov 22nd 2022, Last edited: Feb 21st 2024

Dr. Leila Khurshid
Medical Reviewer Dr. Leila Khurshid PharmD, BCPS

Dr. Leila Khursid is a medical reviewer with a Doctor of Pharmacy degree and completed a PGY1 Pharmacy Residency from St. Mark's Hospital.

Content reviewed by a medical professional. Last reviewed: Nov 23rd 2022