Mirtazapin Actavis (Mirtazapine)

• Mirtazapine is indicated for depressive disorders and works by modulating noradrenergic and serotonergic pathways, offering a distinct pharmacological profile compared with selective serotonin reuptake inhibitors.
• Major depressive disorder: reduces depressive symptoms and improves mood in adult patients.
• Treatment‑resistant depression: may be used as an alternative when other antidepressants have not achieved adequate response.
• Depressive episodes associated with chronic illness: may help improve quality of life and functional status.

• Mirtazapine acts as an antagonist at central presynaptic α2‑adrenergic receptors, increasing the release of norepinephrine and serotonin. It also blocks postsynaptic 5‑HT2 and 5‑HT3 receptors while sparing 5‑HT1A, which enhances serotonergic transmission and contributes to its antidepressant and anxiolytic effects. Additionally, the drug exhibits strong antagonism of histamine H1 receptors, which can lead to sedation and increased appetite. Its combined receptor profile results in a rapid onset of mood improvement in many patients.

Mirtazapine may cause a range of adverse reactions, which are generally classified by frequency.

Common Side Effects

• Sedation or drowsiness: may affect daytime alertness, especially at treatment initiation.
• Increased appetite and weight gain: often leads to noticeable weight increase over weeks.
• Dry mouth: reduced salivation causing discomfort.
• Constipation: slowed gastrointestinal motility.
• Dizziness: may cause light‑headedness when standing quickly.
• Blurred vision: occasional visual disturbances, usually transient.

Serious or Rare Side Effects

• Agranulocytosis or severe neutropenia: marked reduction in white blood cells, increasing infection risk.
• Seizures: rare occurrence, particularly in patients with a seizure history.
• Hepatic dysfunction or jaundice: signs include elevated liver enzymes and yellowing of skin or eyes.

These effects vary in frequency and severity, and patients should be monitored regularly.

When prescribing Mirtazapine, clinicians should consider several precautionary measures to ensure patient safety.

• Assess hepatic function: evaluate liver enzymes before initiating therapy and periodically thereafter.
• Monitor weight and appetite: significant increases may require dietary counseling or dose adjustment.
• Evaluate for suicidal thoughts: especially during the first weeks of treatment in younger adults.
• Use caution in the elderly: increased risk of sedation and falls warrants lower starting doses.
• Store at ambient temperature: keep below 25 °C in the original container, protected from moisture and light.

Mirtazapine can interact with other medicines, altering its efficacy or safety profile.

Major Interactions (Avoid)

• Monoamine oxidase inhibitors (MAOIs): concurrent use can precipitate a hypertensive crisis or severe serotonin syndrome due to excessive monoamine activity.
• Linezolid or other reversible MAO‑A inhibitors: combined therapy raises the risk of serious serotonin toxicity, requiring strict avoidance.
• Other serotonergic agents such as SSRIs, SNRIs, or tramadol: may synergistically increase serotonin levels, heightening the possibility of serotonin syndrome.

Moderate Interactions (Monitor Closely)

• CNS depressants such as benzodiazepines or alcohol: additive sedation may impair cognition and increase respiratory depression risk.
• Antihypertensive drugs: mirtazapine’s α2‑adrenergic blockade can enhance blood‑pressure‑lowering effects, so monitor BP.
• CYP3A4 inhibitors like ketoconazole or erythromycin: may raise mirtazapine levels, increasing both efficacy and side‑effect potential.