Mirtazapina Zentiva (Mirtazapine)

Mirtazapine is used within the antidepressant therapeutic pathway to manage depressive disorders.

• Major depressive disorder (acute phase): reduces depressive symptoms and improves mood.
• Major depressive disorder (maintenance): helps prevent relapse after initial response.
• Major depressive disorder with insomnia: promotes sleep and alleviates associated fatigue.

• Mirtazapine acts as an antagonist at central presynaptic α2‑adrenergic receptors, increasing norepinephrine release, and blocks 5‑HT2 and 5‑HT3 serotonin receptors while also antagonizing H1 histamine receptors. This combined activity enhances noradrenergic and serotonergic neurotransmission and produces sedative and anxiolytic effects that contribute to its antidepressant action.

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

Common Side Effects

• Sedation: drowsiness or feeling unusually sleepy.
• Increased appetite and weight gain: noticeable rise in food intake and body weight.
• Dry mouth: reduced salivation leading to oral discomfort.
• Constipation: infrequent bowel movements or difficulty passing stool.
• Dizziness: sensation of light‑headedness, especially when standing.

Serious or Rare Side Effects

• Agranulocytosis: severe reduction in white blood cells requiring immediate medical attention.
• Severe hypersensitivity reactions: rash, swelling, or anaphylaxis.
• Suicidal thoughts or behavior: emergence or worsening of suicidal ideation.
• Serotonin syndrome: confusion, rapid heart rate, and high fever when combined with other serotonergic agents.
• Hepatic dysfunction: abnormal liver enzymes indicating potential liver injury.

Before initiating therapy with Mirtazapine, several precautionary measures should be considered.

• Psychiatric assessment: monitor for worsening depression or emergence of suicidal thoughts.
• Hepatic function: evaluate liver status and adjust use in severe impairment.
• Renal function: assess kidney health, especially in patients with severe renal disease.
• Discontinuation: avoid abrupt stopping; taper the dose under medical supervision.
• Pregnancy and lactation: prescribe only if potential benefits outweigh potential risks.
• Store at ambient temperature: keep in the original packaging, protect from moisture and light.

Mirtazapine can interact with other medicines, influencing its safety and effectiveness.

Major Interactions (Avoid)

• Monoamine oxidase inhibitors (MAOIs): risk of serotonin syndrome.
• Linezolid or other serotonergic antibiotics: potential for serotonin syndrome.
• Potent CYP2D6 inhibitors (e.g., fluoxetine, paroxetine): may increase mirtazapine plasma concentrations.

Moderate Interactions (Monitor Closely)

• Central nervous system depressants (alcohol, benzodiazepines): additive sedation.
• Anticholinergic agents (e.g., diphenhydramine): increased dry mouth and constipation.
• Other antidepressants (SSRIs, SNRIs): monitor for enhanced serotonergic effects.