What is the main side effect of mirtazapine?

Mirtazapine is an antidepressant medication that is used to treat depression, anxiety, and other mental health conditions. While it can be effective for many people, it can also cause side effects, some of which may be significant. Here is an overview of the main side effect of mirtazapine:

What is the main side effect of mirtazapine?
What is the main side effect of mirtazapine?


One of the most common side effects of mirtazapine is sedation, or drowsiness. Mirtazapine is known for its sedative properties, and many people take it at night to help them sleep. However, sedation can be a problem for some people, particularly if it causes excessive drowsiness or interferes with daily activities.

Other potential side effects of mirtazapine include:

  1. Increased appetite and weight gain: Mirtazapine can increase appetite and cause weight gain in some people. This is thought to be due to the medication’s effects on certain neurotransmitters, including serotonin and histamine.
  2. Dry mouth: Mirtazapine can cause dry mouth, which can be uncomfortable and increase the risk of dental problems.
  3. Dizziness and lightheadedness: Mirtazapine can cause dizziness and lightheadedness, particularly when standing up from a sitting or lying position.
  4. Constipation: Mirtazapine can slow down bowel movements and cause constipation in some people.
  5. Sexual side effects: Mirtazapine can cause sexual side effects, including decreased libido and difficulty achieving orgasm.

It is important to note that not everyone who takes mirtazapine will experience these side effects, and some people may experience different or no side effects at all. Anyone experiencing side effects or other concerning symptoms while taking mirtazapine should speak with their healthcare provider.

There are various forms of drugs available, such as tablets or liquids, and each may have a separate patient information leaflet (PIL) for different doses. It is important to refer to the PIL for the specific form and dose of the drug that you have been prescribed.

You can search for further information and PILs on websites such as:

  • The British National Formulary (BNF)
  • Electronic medicines compendium (emc)
  • The National Library of Medicine's DailyMed
  • The Food and Drug Administration (FDA) 
  • Different drug forms like tablets or liquids have specific patient information leaflets (PIL) for various doses. Refer to the PIL for your prescribed drug form and dose.

    Search for PILs on websites like:


    • ANSM (Agence nationale de sécurité du médicament et des produits de santé): ansm.sante.fr


    • AEMPS (Agencia Española de Medicamentos y Productos Sanitarios): aemps.gob.es


    • BfArM (Bundesinstitut für Arzneimittel und Medizinprodukte): bfarm.de


    For questions about your medication:

    • Consult your doctor, a healthcare professional, or a pharmacist


    • Contact SOS Médecins: 3624
    • For mental health support, contact SOS Suicide: 01 45 39 40 00

    Belgium (French)

    Switzerland (French)

    • La Main Tendue: 143
    • Website: 143.ch

    Canada (French)

    • Centre de prévention du suicide du Québec: 1 866 APPELLE (1 866 277-3553)
    • Website: cpsquebec.ca


    • Contact emergency number: 112
    • For mental health support, contact Teléfono de la Esperanza: 717 003 717


    • Contact emergency number: 112
    • For mental health support, contact Telefonseelsorge: 0800 111 0 111 or 0800 111 0 222


    • Contact emergency number: 112
    • For mental health support, contact Telefono Amico: 199 284 284


    • Contact emergency number: 112
    • For mental health support, contact 113 Zelfmoordpreventie: 0800 0113


    • Contact emergency number: 112
    • For mental health support, contact Sos Voz Amiga: 21 354 45 45, 91 280 26 69, or 96 352 46 60

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