Mirtazapina Doc (Mirtazapine)

Mirtazapine is a noradrenergic and specific serotonergic antidepressant used primarily in depressive disorders.

• Major depressive disorder: reduces depressive symptoms and improves overall mood.
• Depressive episodes in bipolar disorder (adjunct): may lessen depressive phase severity when combined with a mood stabiliser.
• Depression associated with chronic medical conditions: helps improve mood in patients with comorbid illnesses.

• Mirtazapine antagonises central presynaptic α2‑adrenergic receptors, enhancing noradrenaline release, and blocks serotonin 5‑HT2 and 5‑HT3 receptors while strongly inhibiting H1 histamine receptors. This combined activity increases serotonergic and noradrenergic neurotransmission, contributing to its antidepressant effect.

Mirtazapine may cause a range of adverse reactions, from mild to serious.

Common Side Effects

• Sedation or drowsiness: feeling unusually sleepy.
• Increased appetite and weight gain: heightened hunger leading to weight increase.
• Dry mouth: reduced salivation.
• Constipation: infrequent or hard stools.
• Dizziness: sensation of light‑headedness.
• Swelling of the limbs: peripheral oedema.

Serious or Rare Side Effects

• Agranulocytosis: severe reduction in white blood cells.
• Severe hypersensitivity: rash, itching, swelling, or difficulty breathing.
• Suicidal thoughts: emergence or worsening of suicidal ideation.
• Hepatic dysfunction: abnormal liver enzymes or jaundice.
• Seizures: occurrence of convulsive episodes.
• Unusual bleeding: spontaneous bruising or prolonged bleeding.

Before initiating therapy, clinicians should evaluate patient history and monitor for specific risks.

• Pregnancy: safety not established; avoid unless benefits outweigh risks.
• Breastfeeding: excreted in milk; consider alternative therapy.
• Elderly patients: start at low dose and monitor for sedation.
• Hepatic impairment: dose adjustment may be required.
• Concomitant CNS depressants: increased risk of excessive sedation.
• Store at ambient temperature: keep below 25 °C, retain in original packaging, protect from moisture.

Mirtazapine can interact with several drug classes, requiring careful management.

Major Interactions (Avoid)

• MAO inhibitors: risk of hypertensive crisis; discontinue MAOI at least 14 days prior.
• CNS depressants (e.g., benzodiazepines, alcohol): profound sedation and respiratory depression.
• CYP1A2 inhibitors (e.g., fluvoxamine): may increase mirtazapine plasma levels.

Moderate Interactions (Monitor Closely)

• CYP2D6 substrates (e.g., codeine, tamoxifen): possible altered metabolism.
• Anticholinergic agents: additive dry mouth and constipation.
• Serotonergic agents (e.g., SSRIs, SNRIs): monitor for serotonin syndrome.