Mirtazapine

1. Introduction

Mirtazapine is a tetracyclic antidepressant (TeCA) used to treat major depressive disorder (MDD). It works by enhancing the activity of norepinephrine and serotonin in the brain through central alpha-2 adrenergic receptor antagonism. Mirtazapine is often chosen for patients with depression who experience insomnia, anxiety, or poor appetite due to its sedative and appetite-stimulating effects.

2. Indications

  • Major depressive disorder (MDD)
  • Generalised anxiety disorder (GAD) (off-label)
  • Post-traumatic stress disorder (PTSD) (off-label)
  • Insomnia (off-label)

3. Dosage

Adults:

  • Initial dose for depression: 15 mg once daily, typically at bedtime.
  • Usual dose range: 15–45 mg once daily.
  • Dose adjustments may be made at intervals of 1–2 weeks based on response.

Elderly:

  • Start with 7.5–15 mg once daily. Adjust cautiously to minimise sedation or dizziness.

Children:

  • Not recommended for children under 18 years for depression unless specifically advised by a psychiatrist.

4. Administration

  • Take once daily, preferably at bedtime, due to its sedative effects.
  • Can be taken with or without food.
  • Orodispersible tablets should be allowed to dissolve on the tongue without water.

5. Forms Available

  • Tablets: 15 mg, 30 mg, 45 mg
  • Orodispersible tablets: 15 mg, 30 mg, 45 mg

6. Side Effects

6.1 Common Side Effects:

  • Drowsiness
  • Increased appetite and weight gain
  • Dry mouth
  • Dizziness

6.2 Less Common Side Effects:

  • Constipation
  • Peripheral oedema
  • Vivid dreams

6.3 Rare but Serious Side Effects:

  • Agranulocytosis (severe drop in white blood cells)
  • Suicidal thoughts, particularly in young adults
  • Serotonin syndrome (when combined with other serotonergic drugs)

7. Warnings

  • Suicidal Ideation: Monitor closely for worsening depression or suicidal thoughts, especially in patients under 25 years.
  • Agranulocytosis: Rare but potentially life-threatening. Discontinue if symptoms like sore throat or fever develop.
  • CNS Effects: May impair ability to drive or operate machinery due to sedation.

8. Precautions

  • Use cautiously in patients with a history of seizures, bipolar disorder, or cardiovascular disease.
  • Avoid abrupt discontinuation to minimise withdrawal symptoms such as anxiety or irritability.
  • Adjust the dose for patients with moderate to severe hepatic or renal impairment.

9. Interactions

  • Monoamine oxidase inhibitors (MAOIs): Risk of hypertensive crisis. Avoid use within 14 days of stopping MAOIs.
  • Benzodiazepines and CNS depressants: Increased sedation.
  • Serotonergic drugs (e.g., SSRIs, SNRIs, St. John’s Wort): Risk of serotonin syndrome.
  • Warfarin: May increase bleeding risk; monitor INR closely.

10. Monitoring Parameters

  • Monitor for improvement in depressive symptoms (e.g., mood, sleep, appetite).
  • Monitor for signs of suicidal thoughts, particularly during the initial weeks of treatment.
  • Regularly assess weight and appetite due to the risk of significant weight gain.
  • Consider periodic blood counts to detect agranulocytosis.

11. Use in Children

  • Not recommended for children under 18 for depression unless prescribed under specialised care. Monitor closely for suicidal ideation if used.

12. Use in Pregnancy

  • Classified as Category C. Use only if benefits outweigh potential risks. Limited data suggests no major teratogenic risks but monitor closely.

13. Use in Elderly

  • Start with lower doses (7.5–15 mg daily) due to increased sensitivity to sedation and dizziness.

14. Use in Kidney Disease

  • Adjust dose in moderate to severe renal impairment.
  • Recommended maximum dose: 30 mg/day in severe renal impairment.

15. Use in Liver Disease

  • Dose adjustment may be required in moderate to severe hepatic impairment. Monitor for adverse effects.

16. Patient Counselling Points

  • Take Mirtazapine once daily at bedtime to reduce daytime drowsiness.
  • Be patient, as the effects on mood may take 2–4 weeks to fully develop.
  • Avoid driving or operating machinery until you know how Mirtazapine affects you.
  • Report any worsening depression, suicidal thoughts, or unusual bleeding immediately.
  • Maintain a healthy diet and monitor weight due to the risk of increased appetite and weight gain.

17. Table of Brand Names, Manufacturer, and Prices in USD

Brand NameManufacturerStrength/Dosage FormPrice (USD)
RemeronOrganon15 mg Tablet$30 (30 tablets)
Remeron SolTabOrganon15 mg Orodispersible Tablet$40 (30 tablets)
Generic MirtazapineVarious30 mg Tablet$15 (30 tablets)

18. 15 FAQs (Frequently Asked Questions)

1. What is Mirtazapine?
Mirtazapine is an antidepressant used to treat major depressive disorder.

2. How does Mirtazapine work?
It enhances norepinephrine and serotonin activity in the brain by blocking central alpha-2 adrenergic receptors.

3. What is the usual dose of Mirtazapine?
The starting dose is 15 mg once daily, with a usual range of 15–45 mg daily.

4. How long does it take for Mirtazapine to work?
It may take 2–4 weeks to notice significant improvement in symptoms.

5. Can Mirtazapine cause weight gain?
Yes, weight gain and increased appetite are common side effects.

6. Can Mirtazapine be used during pregnancy?
It is generally avoided unless the benefits outweigh the risks. Consult your doctor.

7. Can Mirtazapine cause drowsiness?
Yes, it is commonly associated with sedation and is often taken at bedtime.

8. Is Mirtazapine safe for children?
It is not typically recommended for children under 18 unless prescribed under specialised care.

9. Can Mirtazapine cause suicidal thoughts?
Yes, especially in young adults under 25 years. Monitor closely for mood changes.

10. How should I stop taking Mirtazapine?
Do not stop abruptly. Gradually reduce the dose under your doctor’s guidance to avoid withdrawal symptoms.

11. Can Mirtazapine interact with other medications?
Yes, it can interact with serotonergic drugs, benzodiazepines, and anticoagulants like warfarin.

12. What should I do if I miss a dose?
Take it as soon as you remember, unless it is close to your next dose. Do not double the dose.

13. Can Mirtazapine be used for anxiety?
Yes, it is often used off-label for generalised anxiety disorder and PTSD.

14. How should Mirtazapine be stored?
Store at room temperature, away from moisture and heat.

15. Can I drink alcohol while taking Mirtazapine?
Avoid alcohol as it may increase sedation and dizziness.