Mirtazapine Activase Pharmaceuticals (Mirtazapine)

Mirtazapine is a NaSSA antidepressant indicated for conditions within the depressive disorder spectrum.

• Major depressive disorder: alleviates depressive symptoms and improves overall mood in adult patients.

• Mirtazapine antagonizes central presynaptic alpha‑2 adrenergic receptors, which enhances norepinephrine release, and blocks 5‑HT2 and 5‑HT3 serotonin receptors as well as H1 histamine receptors. This combined action increases serotonergic and noradrenergic neurotransmission while providing sedative and appetite‑stimulating effects, contributing to its antidepressant efficacy.

Mirtazapine may cause a range of adverse reactions that vary in frequency and severity.

Common Side Effects

• Sedation or somnolence: feeling unusually sleepy or drowsy.
• Increased appetite and weight gain: heightened hunger leading to weight increase.
• Dry mouth: reduced salivation causing oral discomfort.
• Constipation: slowed gastrointestinal motility.
• Dizziness: sensation of light‑headedness or unsteadiness.
• Fatigue: general feeling of tiredness.

Serious or Rare Side Effects

• Agranulocytosis or severe neutropenia: markedly reduced white blood cells.
• Seizures: occurrence of convulsive episodes.
• Hypersensitivity reactions: rash, itching, swelling, or anaphylaxis.
• Serotonin syndrome: rare but potentially life‑threatening condition when combined with other serotonergic agents.
• Suicidal thoughts or behavior: emergence or worsening of suicidal ideation.
• Hepatic dysfunction: abnormal liver enzyme elevations.

Before initiating therapy, clinicians should consider several safety measures.

• Assess hepatic function: adjust use in patients with severe liver impairment.
• Monitor for worsening depression or suicidal ideation, especially at treatment onset.
• Use caution in elderly patients: increased risk of sedation and falls.
• Avoid abrupt discontinuation: taper to reduce withdrawal symptoms.
• Pregnancy and lactation: safety not established; weigh benefits against potential risks.
• Store at ambient temperature: keep below 25°C, protect from moisture and light in the original container.

Mirtazapine can interact with other medicines, requiring careful management.

Major Interactions (Avoid)

• Monoamine oxidase inhibitors (MAOIs): risk of severe hypertensive or serotonergic reactions.
• 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.

Moderate Interactions (Monitor Closely)

• CYP2D6 inhibitors (e.g., fluoxetine, paroxetine): may raise mirtazapine plasma levels.
• Carbamazepine or other enzyme inducers: may reduce mirtazapine effectiveness.
• Antihistamines: potential for enhanced sedation.
• Warfarin: possible alteration of INR; monitor coagulation parameters.
• Lithium: monitor lithium levels for potential toxicity.