Mirtazapine; Uses, Dosage, Side Effects, Interactions

Mirtazapine; Uses, Dosage, Side Effects, Interactions

Mirtazapine is a synthetic tetracyclic derivative of the piperazine-azepines with antidepressant activity. Although its mechanism of action is unknown, mirtazapine enhances central adrenergic and serotonergic transmission, possibly by acting as an antagonist at central presynaptic alpha 2 adrenergic inhibitory autoreceptors and heteroreceptors. This agent is a potent antagonist of 5-hydroxytryptamine type 2 (5-HT2), 5-HT3, and histamine 1 (H1) receptors, and a moderate antagonist of peripheral alpha 1 adrenergic and muscarinic receptors.

Mirtazapine is a tetracyclic antidepressant with a somewhat unique mechanism of action. Mirtazapine therapy can be associated with transient asymptomatic elevations in serum aminotransferase levels and has been linked to rare instances of clinically apparent acute liver injury.

Mirtazapine has a tetracyclic chemical structure and belongs to the piperazine-azepine group of compounds. It is designated 1,2,3,4,10,14b-hexahydro-2-methylpyrazino [2,1-a] pyrido [2,3-c] benzazepine and has the empirical formula of C17H19N3.Primarily in the treatment of depression. In addition to its antidepressant properties, mirtazapine has anxiolytic, sedative, antiemetic, and appetite stimulant effects and is sometimes used in the treatment of anxiety disorders, insomnia, nausea and vomiting, and to produce weight gain when desirable. It is taken by mouth. The drug acts as an antagonist of certain adrenergic and serotonin receptors and is also a strong antihistamine. It is sometimes described as a noradrenergic and specific serotonergic antidepressant (NaSSA), although the actual evidence in support of this label has been regarded as poor.

Mechanism of Action of Mirtazapine

Mirtazapine acts as an antagonist at central pre-synaptic alpha(2)-receptors, inhibiting negative feedback to the presynaptic nerve and causing an increase in NE release. Blockade of heteroreceptors, alpha(2)-receptors contained in serotonergic neurons, enhances the release of 5-HT, increasing the interactions between 5-HT and 5-HT1 receptors and contributing to the anxiolytic effects of mirtazapine. Mirtazapine also acts as a weak antagonist at 5-HT1 receptors and as a potent antagonist at 5-HT2 (particularly subtypes 2A and 2C) and 5-HT3 receptors. Blockade of these receptors may explain the lower incidence of adverse effects such as anxiety, insomnia, and nausea. Mirtazapine also exhibits significant antagonism at H1-receptors, resulting in sedation. Mirtazapine has no effects on the reuptake of either NE or 5-HT and has only minimal activity at dopaminergic and muscarinic receptors.

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Indications of Mirtazapine

Contra-Indications of Mirtazapine

  • High cholesterol
  • The high amount of triglyceride in the blood
  • Low amount of sodium in the blood
  • Extreme loss of body Water
  • Behaving with excessive cheerfulness and activity
  • A mild degree of mania
  • Having thoughts of suicide
  • Neuroleptic malignant syndrome
  • Closed angle glaucoma
  • Heart attack
  • Angina
  • Very rapid heartbeat
  • Prolonged QT interval on EKG
  • Abnormal EKG with QT changes from birth
  • stroke
  • Disorder of the blood vessels of the brain
  • Blood pressure drop upon standing
  • Abnormally low blood pressure
  • Liver problems

Dosage of Mirtazapine

Strengths: 7.5mg; 15 mg; 30 mg; 45 mg;


  • Initial dose: 15 mg orally once a day at bedtime
  • Maintenance dose: 15 to 45 mg orally once a day
  • Maximum dose: 45 mg/day

Side Effects

The most common

More common

Less common

  • Abnormal dreams
  • change in sense of taste
  • congestion
  • discouragement, feeling sad, or empty
  • Suicide attempts
  • Acting on dangerous impulses
  • Aggressive or violent behavior
  • Thoughts about suicide or dying
  • New or worse depression
  • New or worse anxiety or panic attacks
  • Agitation, restlessness, anger, or irritability
  • Trouble sleeping
  • An increase in activity or talking more than normal
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Drug Interactions of Mirtazapine

Mirtazapine may interact with following drugs, supplements & may decrease the efficacy of the drug

Pregnancy & Lactation of Mirtazapine

 FDA Pregnancy Category C 


This medication should not be used during pregnancy unless the benefits outweigh the risks. It has been reported that babies born to women who have taken mirtazapine during the last trimester of pregnancy may experience complications that result in an increase in the length of their hospital stay. If you become pregnant while taking this medication, contact your doctor immediately.

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It is not known if mirtazapine passes into breast milk. If you are a breastfeeding mother and are taking this medication, it may affect your baby. Talk to your doctor about whether you should continue breastfeeding.





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