Mirtazapin Viatris (Mirtazapine)

Mirtazapin Viatris is a NaSSA antidepressant indicated for several depressive disorders.

• Major depressive disorder: reduces depressive symptoms and improves mood in adults.
• Depressive disorder with melancholic features: alleviates low mood, loss of pleasure and early morning awakening.
• Depressive disorder with atypical features: helps restore appetite, weight and energy levels.

• Mirtazapine acts as an antagonist at central presynaptic α2‑adrenergic receptors, increasing noradrenaline release, and blocks postsynaptic 5‑HT2 and 5‑HT3 receptors, enhancing serotonergic transmission. It also antagonises histamine H1 receptors, contributing to its sedative profile. These combined actions raise noradrenergic and serotonergic neurotransmission, which underlies its antidepressant effect.

Mirtazapin Viatris may cause a range of adverse reactions, most of which are dose‑related and reversible.

Common Side Effects

• Sedation or drowsiness: feeling unusually sleepy, especially after the first weeks of therapy.
• Increased appetite and weight gain: heightened hunger leading to modest weight increase.
• Dry mouth: reduced salivation causing a dry sensation in the mouth.
• Constipation: slowed intestinal motility resulting in infrequent bowel movements.

Serious or Rare Side Effects

• Agranulocytosis: severe reduction in white blood cells, requiring immediate medical attention.
• Seizures: rare occurrence of convulsive episodes, particularly in predisposed individuals.
• Severe hypersensitivity: rash, swelling, or difficulty breathing indicating an allergic reaction.

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

• Cardiovascular assessment: check for existing heart disease or arrhythmias.
• Liver or renal impairment: adjust monitoring if hepatic or renal function is compromised.
• Concomitant CNS depressants: avoid excessive sedation when combined with alcohol or other sedatives.
• Pregnancy and lactation: weigh potential benefits against unknown fetal risks.
• Store at ambient temperature: keep below 25 °C, retain in original packaging, protect from moisture and direct sunlight.

Mirtazapin Viatris can alter the effect of several co‑administered medicines.

Major Interactions (Avoid)

• Monoamine oxidase inhibitors (MAOIs): risk of serotonin syndrome; a washout period is required.
• Potent CYP2D6 inhibitors (e.g., fluoxetine, paroxetine): may increase mirtazapine plasma levels.

Moderate Interactions (Monitor Closely)

• CNS depressants (benzodiazepines, opioids): enhanced sedation and respiratory depression.
• Anticholinergic agents: additive dry mouth and constipation.
• Warfarin: possible alteration of INR, requiring closer coagulation monitoring.