Mirtazapin Krka (Mirtazapine)

Mirtazapine is a NaSSA antidepressant that acts on neurotransmitter pathways implicated in mood disorders.

• Major depressive disorder: reduces depressive symptoms and improves overall mood in adults.
• Depressive episodes with prominent anxiety: alleviates anxiety and improves sleep quality alongside mood.
• Treatment‑resistant depression: used as an alternative when first‑line antidepressants are ineffective.

• Mirtazapine exerts its antidepressant effect primarily by antagonising central presynaptic α2‑adrenergic receptors, which increases the release of norepinephrine and serotonin. It also blocks postsynaptic 5‑HT2 and 5‑HT3 receptors, enhancing serotonergic transmission while reducing associated side effects such as nausea and insomnia. The combined actions lead to improved mood and sleep regulation.

Mirtazapine may be associated with a range of adverse reactions, which are categorised by frequency and severity.

Common Side Effects

• Sedation or drowsiness
• Increased appetite and weight gain
• Dry mouth
• Constipation
• Dizziness
• Peripheral edema

Serious or Rare Side Effects

• Agranulocytosis or severe neutropenia
• Severe hypersensitivity reactions (rash, angioedema)
• Suicidal thoughts or behaviour, especially early in treatment
• Serotonin syndrome when combined with other serotonergic agents
• Hepatotoxicity
• Unusual bleeding

When prescribing Mirtazapine, clinicians should consider several safety precautions to minimise risk.

• Assess hepatic function: evaluate liver enzymes before initiating therapy.
• Monitor for suicidal ideation: especially during the first weeks of treatment.
• Use cautiously in elderly patients: increased sensitivity to sedation and falls.
• Avoid abrupt discontinuation: taper the dose to reduce withdrawal symptoms.
• Adjust dose in renal impairment: consider lower doses in severe renal dysfunction.
• Store at ambient temperature: keep in the original container, protect from moisture and light.

Mirtazapine can interact with other medicines, and the clinical relevance varies from major to moderate.

Major Interactions (Avoid)

• Monoamine oxidase inhibitors (MAOIs): risk of hypertensive crisis and serotonin syndrome.
• Linezolid or other reversible MAO‑A inhibitors: may precipitate serotonin excess.
• Other serotonergic agents (e.g., SSRIs, SNRIs, tramadol): increased risk of serotonin syndrome.

Moderate Interactions (Monitor Closely)

• Benzodiazepines or other CNS depressants: additive sedation.
• CYP2D6 inhibitors (e.g., fluoxetine, paroxetine): may increase mirtazapine plasma levels.
• CYP3A4 inhibitors (e.g., ketoconazole, erythromycin): can raise drug exposure.
• Alcohol: enhances central nervous system depression.
• Antihistamines: may increase sedation and anticholinergic effects.