Mirtazapin - Use | Side Effects | Dosage

This article was medically reviewed by M.Pharm, Marko Tanaskovic on August 12, 2018. To read more about an author, click here.

Mirtazapin (also known as mirtazapine) belongs to a group of medications known as antidepressants. It preferentially blocks the alpha 2 receptors as well as 5HT-1, 5HT-2 and 5HT-3 receptors, thereby improving the balance of neurotransmitters and hormones (increase serotonin concentration). Serotonin is important mood hormone (often called the happiness hormone). This medicine is used in the treatment of major depression.


Mirtazapin should be avoided in combination with medications known as MAO inhibitors, that are also used in the treatment of depression, such as:

  • moclobemide,
  • isocarboxazid,
  • phenelzine and others.

If you are already taking some of these medicines, you should quit the MAO inhibitor for at least two weeks before you start to take this drug. Concomitant use of Mirtazapin with these medications may cause serious side effects (e.g. serotonin syndrome). Symptoms of serotonin syndrome include:

  1. mood swings,
  2. confusion,
  3. irritability,
  4. seizures muscle spasms,
  5. increase of emotions,
  6. delirium and coma!

For the same reason, this drug should be avoided in patients taking medicines known as selective serotonin reuptake inhibitors (SSRIs), such as:

  • sertraline,
  • fluoxetine,
  • paroxetine,
  • fluvoxamine,
  • citalopram,
  • escitalopram and others.

It should be avoided in patients allergic to mirtazapin or other similar drugs.

This medicine should be avoided in patients under the age of 18, because suicidal ideation is more common in younger patients. Patients and their families should pay close attention to any changes in behavior, mood and thought.

This drug can cause agranulocytosis (decrease in the number of white blood cells), therefore you will be more susceptible to the infections, which can even be fatal! This side effect occurs very rarely, but patients above the age of 65 are at greater risk.

Mirtazapin should be used only with extra precautions in the following conditions:

  • In patients with epilepsy
  • Patients with liver damage. This medicine is excreted through the liver and can further worsen the condition in patients who already have liver damage. If you are experiencing any symptoms of liver damage, such as:
    • pain in the right upper abdomen,
    • loss of appetite,
    • nausea,
    • jaundice (yellowing of the skin and eyes), contact your doctor immediately
  • In patients with heart diseases
  • Patients with diabetes
  • In patients with prostate enlargement
  • In patients with glaucoma (increased eye pressure)
  • In patients with electrolyte imbalance (sodium, potassium, magnesium)

Use during pregnancy and breastfeeding

Calixta should be avoided during pregnancy unless the benefit to the mother outweighs the risk to the child. It is possible that this drug can cause withdrawal syndrom in newborns.

This medicine passes into breast milk, therefore breastfeeding should be avoided.

How to use

Mirtazapin should be taken once a day at bedtime. The dose of Mirtazapin will depend on your condition and age (dose range: 15 mg to 40 mg once a day). Treatment usually begins at a low dose followed by gradual dose increase until the desired effect is achieved. It may take at least one month before your symptoms improve. You should take this medicament before bedtime, because this medicine can cause sedation or sleepiness.

When you need to stop your treatment with this drug, you should not stop your medication suddenly. Your doctor will probably decrease your dose gradually.

Example: If you are taking 30 mg once daily, the dose should first be reduced to 15 mg once daily, and administered during one week, and then you can stop your medication.

Use with other medicines (Interactions)

Calixta should be avoided in combination with the following drugs:

  • Medicines used in the treatment of depression, such as:
    • moclobemide,
    • phenelzine,
    • isocarboxazid,
    • tranylcypromine,
    • sertraline,
    • fluoxetine,
    • paroxetine,
    • fluvoxamine,
    • citalopram,
    • escitalopram, and others. Concomitant use of these medications with Mirtazapin, can cause serotonin syndrome!
  • Benzodiazepines, drugs used in the treatment of insomnia and anxiety disorders, such as:
    • diazepam,
    • bromazepam,
    • lorazepam,
    • nitrazepam,
    • prazepam, and others. Mirtazapin may increase the effect of these drugs increasing the risk of side effects.
  • Warfarin, a drug used in the treatment of thrombosis. Concomitant use with this drug increases the risk of bleeding.
  • Drugs used in the treatment of epilepsy, such as:
    • phenytoin,
    • carbamazepine,
    • phenobarbital. These drugs decrease the level of Mirtazapin in the blood, therefore reducing its efficacy.
  • Drugs used in to treat cold and other infections (antibiotics), such as:
    • erythromycin,
    • clarithromycin,
    • azithromycin, and others. These drugs increase the level of Mirtazapin in the blood, increasing the risk of side effects.
  • Drugs used in the treatment of fungal infections, such as:
    • ketoconazole,
    • fluconazole,
    • itraconazole, and others. These drugs increase the level of Mirtazapin in the blood, increasing the risk of side effects
  • St. John's Wort.

Mirtazapin should not be used in combination with alcoholic beverages, as it may cause serious side effects.

Side effects

Mirtazapin may cause the following side effects:

  1. nausea,
  2. vomiting,
  3. diarrhea,
  4. drowsiness,
  5. lethargy,
  6. headache,
  7. dizziness,
  8. tremors,
  9. restless legs syndrome,
  10. agranulocytosis (decrease in the number of white blood cells),
  11. serotonin syndrome,
  12. muscle pain,
  13. joint pain,
  14. increased appetite,
  15. weight gain,
  16. low blood pressure,
  17. hallucinations,
  18. nightmares,
  19. liver damage,
  20. low blood sodium level (hiponatremia),
  21. allergy and others.

Tell your doctor immediately if you are experiencing any side effects.

Information on this website are provided for educational purposes only and are not intended for medical advice, diagnosis or treatment.

If you have any concerns or questions about your health, you should always consult with a physician or other health-care professional.

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