[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [Pharmacology](https://durgical.com/en/pharmacology/) › [Atypical antidepressants](https://durgical.com/en/pharmacology/classes/atypical-antidepressants/) › Mirtazapine

[Pharmacology](https://durgical.com/en/pharmacology/) · [Atypical antidepressants](https://durgical.com/en/pharmacology/classes/atypical-antidepressants/)

# Mirtazapine

An antidepressant that blocks alpha-2 receptors to release more norepinephrine and serotonin. Causes sleepiness and appetite gain; rarely, low white cells.

Updated 2026-11-01

- Class: [Atypical antidepressants](https://durgical.com/en/pharmacology/classes/atypical-antidepressants/)
- Receptor: Alpha-2A adrenergic receptor (also 5-HT2, 5-HT3 and H1 receptors)
- ATC code: N06AX11

## Mechanism of action

Mirtazapine blocks presynaptic alpha-2 adrenergic autoreceptors and heteroreceptors, which normally act as a brake on release, so noradrenergic and serotonergic neurons release more transmitter. It also blocks 5-HT2 and 5-HT3 receptors, which may limit some serotonergic side effects (nausea, sexual dysfunction), and strongly blocks H1 receptors (sleepiness, appetite).

- Mirtazapine blocks presynaptic alpha-2 receptors
- The brake is removed: more norepinephrine and serotonin are released
- 5-HT2 and 5-HT3 block limits nausea and sexual side effects
- H1 block causes sleepiness and more appetite

## Pharmacokinetics

**Absorption**
By mouth, as tablets or orally disintegrating tablets

**Metabolism**
Extensive in the liver

**Half-life**
About 20 to 40 hours; longer in women and older adults

## Indications

- Major depressive disorder in adults

## Adverse effects

### Common

- Somnolence
- Increased appetite and weight gain
- Dry mouth and constipation
- Dizziness
- Rise in cholesterol and triglycerides

### Serious (rare, important)

- Agranulocytosis and severe neutropenia (rare)
- Suicidal thoughts and behaviour in young people (boxed warning)
- Serotonin syndrome
- QT prolongation and torsades de pointes
- DRESS and other severe skin reactions
- Hyponatraemia
- Seizures
- Angle-closure glaucoma

## Contraindications

- MAO inhibitors, including linezolid and intravenous methylene blue, or within 14 days of stopping an MAOI
- Hypersensitivity to mirtazapine

## Key interactions

**Alcohol, benzodiazepines and other sedatives**
Additive sedation and impaired motor skills

**MAO inhibitors and other serotonergic drugs**
Serotonin syndrome

**Drugs that prolong the QT interval**
Additive risk of arrhythmia

**Strong CYP3A inhibitors or inducers**
Higher or lower mirtazapine levels

## What is monitored

- Signs of infection (fever, sore throat, mouth ulcers) with a white cell count if they appear
- Weight and lipids
- Mood and suicidal thoughts
- Sodium in older adults

## Administration and safety

- Given by mouth, preferably in the evening at bedtime because of sleepiness
- Orally disintegrating tablets dissolve on the tongue
- Stopped gradually

## Nursing care

- Teach the person to report fever, sore throat or mouth ulcers promptly (possible agranulocytosis)
- Track weight and appetite, and warn about drowsiness when driving
- Avoid alcohol and other sedatives
- Assess suicidal thoughts early in treatment and after dose changes

## Pregnancy and breastfeeding

Long experience in pregnancy has not reliably shown a drug-related risk of major birth defects or miscarriage; untreated depression also carries risks.

## Memory aid

Mirtazapine makes you «Munch and snooze»: appetite and sleep go up, so it suits the thin, sleepless older patient.

## Test yourself

Think of the answer, then tap the question to see it.

## How does mirtazapine increase norepinephrine and serotonin release without blocking reuptake?

It blocks presynaptic alpha-2 autoreceptors and heteroreceptors, removing the negative feedback on release.

## Which two side effects make mirtazapine useful for a depressed older adult with insomnia and weight loss?

Sedation and increased appetite with weight gain, mainly from H1 block.

## A patient on mirtazapine has fever and sore throat. What test is needed and why?

A white cell count, because mirtazapine can rarely cause agranulocytosis; it is stopped if the count is low.

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## Related drugs

- [Trazodone](https://durgical.com/en/pharmacology/trazodone/)
- [Bupropion](https://durgical.com/en/pharmacology/bupropion/)

[← Back to the class: Atypical antidepressants](https://durgical.com/en/pharmacology/classes/atypical-antidepressants/)

Educational content on how drugs work; not a prescribing guide and no substitute for a health professional's advice. No doses are given.

Sources: [DailyMed - MIRTAZAPINE tablet, film coated](https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=a4c012f0-50b6-42fb-9f06-a14632f23f2e) (DailyMed (U.S. National Library of Medicine), 2026); [Mirtazapine: MedlinePlus Drug Information](https://medlineplus.gov/druginfo/meds/a697009.html) (MedlinePlus (U.S. National Library of Medicine), 2025); [ATCDDD - ATC/DDD Index](https://atcddd.fhi.no/atc_ddd_index/?code=N06AX) (WHO Collaborating Centre for Drug Statistics Methodology, 2026).

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Source: https://durgical.com/en/pharmacology/mirtazapine/
License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/pharmacology/mirtazapine/