What is the usual dose of mirtazapine for depression vs insomnia?

Mirtazapine Dosing for Depression vs Insomnia

For depression, mirtazapine should be dosed at 15-45 mg daily, while for insomnia alone, a lower dose of 7.5-15 mg at bedtime is typically effective.

Dosing for Depression

Initial Dosing

• Start with 15 mg once daily, administered orally in the evening prior to sleep 1
• Allow 1-2 weeks between dose adjustments to properly evaluate response 1
• Titrate upward if needed, using increments of the initial dose

Maintenance Dosing

• Effective dosage range: 15-45 mg daily 2, 1
• Maximum recommended dose: 30 mg at bedtime according to guidelines 2
• A full therapeutic trial requires 4-8 weeks to determine efficacy 2

Therapeutic Considerations

• Mirtazapine is potent and well-tolerated for depression 2
• The onset of clinical effect typically occurs in 2-4 weeks, though sleep disturbances and anxiety symptoms may improve within the first week 3
• Higher doses (30-45 mg) tend to be less sedating than lower doses due to increased noradrenergic effects at higher doses

Dosing for Insomnia

Initial Dosing

• For insomnia without depression: 7.5 mg at bedtime 2
• Lower doses (7.5-15 mg) are more sedating than higher doses due to predominant H1 receptor antagonism

Therapeutic Considerations

• Mirtazapine is effective for insomnia in patients with autism spectrum disorders at doses starting at 7.5 mg 2
• It promotes sleep, appetite, and weight gain even at lower doses 2
• Particularly effective for sleep maintenance insomnia and may help with early morning awakenings 4

Dosing Algorithm

1. For primary depression with sleep disturbance:

   • Start with 15 mg at bedtime
   • Assess response after 1-2 weeks
   • If inadequate response, increase by 15 mg increments up to 45 mg daily
   • Maximum dose: 45 mg daily

2. For primary insomnia without significant depression:

   • Start with 7.5 mg at bedtime
   • Maintain at lower dose (7.5-15 mg) if effective for sleep
   • Do not exceed 15 mg if treating insomnia alone

Important Clinical Considerations

• Pharmacological mechanism: At lower doses (≤15 mg), mirtazapine primarily blocks histamine H1 receptors, producing sedation. At higher doses, increased noradrenergic and serotonergic effects become more prominent, potentially reducing sedation 5

• Common side effects:

  • Somnolence (especially at lower doses)
  • Increased appetite and weight gain
  • Dizziness 6, 5

• Monitoring:

  • Follow up within 7-10 days of initiating treatment to assess sleep quality and side effects 4
  • Monitor for increased appetite and weight gain, which may worsen sleep apnea 4

• Discontinuation:

  • Gradually reduce the dosage rather than stopping abruptly to prevent withdrawal symptoms 1
  • Taper over 10-14 days when discontinuing 2

• Drug interactions:

  • Avoid concurrent use with MAOIs (allow 14 days between stopping one and starting the other) 1
  • Dose adjustments may be needed with strong CYP3A inducers or inhibitors 1

Mirtazapine offers the advantage of improving sleep without the tolerance or dependence issues associated with benzodiazepines, making it a valuable option for patients with both depression and insomnia 4.