Mirtazapina Viatris (Mirtazapine)

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

• Major depressive disorder: reduces depressive symptoms and improves mood in adult patients.
• Bipolar depression (adjunct): used as an add‑on therapy to manage depressive episodes in bipolar I disorder.
• Depression with insomnia: helps alleviate depressive symptoms while improving sleep quality in patients who have concurrent insomnia.

• Mirtazapine antagonizes central presynaptic α2‑adrenergic receptors, which increases norepinephrine release, and blocks postsynaptic 5‑HT2 and 5‑HT3 receptors, enhancing serotonergic transmission. It also blocks histamine H1 receptors, contributing to its sedative properties. The combined actions raise synaptic concentrations of norepinephrine and serotonin, producing antidepressant effects.

Mirtazapine is associated with a range of adverse reactions that vary in frequency and severity.

Common Side Effects

• Sedation or drowsiness
• Increased appetite and weight gain
• Dry mouth
• Constipation
• Dizziness
• Orthostatic hypotension

Serious or Rare Side Effects

• Agranulocytosis or severe neutropenia
• Hepatic dysfunction or jaundice
• Severe hypersensitivity reactions (rash, angioedema)
• Suicidal thoughts or behavior, especially early in treatment
• Serotonin syndrome when combined with other serotonergic agents
• Seizures (rare)

Mirtazapine requires careful clinical monitoring to ensure safe use.

• Hepatic function: assess liver enzymes before initiating therapy.
• Suicidal ideation: monitor patients for worsening depression or emergent suicidal thoughts.
• Elderly patients: use caution due to increased risk of sedation and falls.
• Discontinuation: avoid abrupt cessation; taper dose under medical supervision.
• Bipolar disorder: screen for manic episodes before prescribing.
• Store at room temperature: keep in the original container, protect from moisture and direct sunlight.

Mirtazapine can interact with several drug classes, necessitating vigilance.

Major Interactions (Avoid)

• Monoamine oxidase inhibitors (MAOIs): risk of hypertensive crisis or serotonin syndrome.
• Other serotonergic agents (e.g., SSRIs, SNRIs, tramadol): increased risk of serotonin syndrome.
• Central nervous system depressants (e.g., benzodiazepines, alcohol): additive sedation and respiratory depression.
• Strong CYP2D6 inhibitors (e.g., paroxetine, fluoxetine): may raise mirtazapine plasma levels.

Moderate Interactions (Monitor Closely)

• Alcohol: may enhance sedative effects.
• Antihistamines: additive drowsiness.
• Carbamazepine: may reduce mirtazapine concentrations.
• Warfarin: monitor INR as occasional interaction reported.
• Fluvoxamine: may increase mirtazapine exposure modestly.