irtazapine (Brand Names in India: Mirtaz, Mirnite, Mirtadep, Remeron)

 

1. Generic Name

Mirtazapine

2. Brand Names

Mirtaz (Sun Pharmaceuticals)

Mirnite (Intas Pharmaceuticals)

Mirtadep (Torrent Pharmaceuticals)

Remeron (Organon India)

 

3. Pharmaceutical Formulation

Tablets: 7.5 mg, 15 mg, 30 mg, 45 mg

 

4. Therapeutic Classification

Tetracyclic Antidepressant

 

5. Indications

Mirtazapine is indicated for:

Major Depressive Disorder (MDD): Adults

Generalized Anxiety Disorder (GAD): Off-label use

Post-Traumatic Stress Disorder (PTSD): Off-label use

Insomnia: Off-label use at lower doses

6. Mechanism of Action

Mirtazapine acts as:

Antagonist of central α2-adrenergic receptors: Enhances the release of norepinephrine and serotonin.

5-HT2 and 5-HT3 receptor antagonist: Reduces serotonergic side effects like nausea and sexual dysfunction.

Histamine H1 receptor antagonist: Contributes to sedation, especially at lower doses.

7. Dosage and Administration

Adults:

Initial Dose: 15 mg at bedtime.

Maintenance Dose: 15–45 mg/day.

Elderly or Hepatic/Renal Impairment: Start with a lower dose (7.5 mg or 15 mg), with cautious titration.

 

8. Onset of Action

Important Note:
Mirtazapine typically shows noticeable improvement in symptoms within 1 to 2 weeks, but full therapeutic effects may take 4 to 6 weeks. Patients should continue medication as prescribed, even if initial improvement is slow.

9. Contraindications

Hypersensitivity to mirtazapine or its excipients.

Concurrent use with monoamine oxidase inhibitors (MAOIs) or within 14 days of discontinuation.

 

10. Warnings and Precautions

Suicidality: Monitor for increased risk of suicidal ideation, especially in younger patients.

Agranulocytosis: Rare but serious; monitor for signs of infection (fever, sore throat).

Weight Gain: Common side effect due to increased appetite.

Sedation: Use caution when operating machinery or driving.

Hepatic and Renal Impairment: Dose adjustment may be necessary.

11. Side Effects

Common:

Increased appetite and weight gain

Sedation, drowsiness

Dry mouth

Dizziness

Serious:

Agranulocytosis (rare)

Serotonin syndrome when combined with serotonergic drugs

Mania or hypomania (in bipolar patients)

12. Drug Interactions

MAOIs: Risk of serotonin syndrome; contraindicated.

Alcohol and CNS depressants: Additive sedation.

Warfarin: Increased bleeding risk.

CYP3A4 inducers/inhibitors: May alter mirtazapine plasma levels.

13. Overdose Management

Symptoms: Sedation, disorientation, tachycardia, agitation, serotonin syndrome (if combined with other serotonergic agents).
Treatment: Symptomatic and supportive care. Gastric lavage and activated charcoal if recent ingestion.

14. Pharmacokinetics

Absorption: Rapidly absorbed, bioavailability ~50%.

Distribution: Protein binding ~85%.

Metabolism: Hepatically metabolized via CYP1A2, CYP2D6, and CYP3A4.

Elimination: Half-life ~20–40 hours, allowing once-daily dosing.

15. Storage and Handling

Store at a temperature below 30°C, protected from light and moisture. Keep out of reach of children.

16. Packaging

Available in blister packs of 10, 20, or 30 tablets.

17. Manufacturer Information

Mirtaz: Sun Pharmaceuticals

Mirnite: Intas Pharmaceuticals

Mirtadep: Torrent Pharmaceuticals

Remeron: Organon India