Can mirtazapine be used for insomnia (sleep disorder)?

Mirtazapine for Insomnia

Mirtazapine is an effective medication for treating insomnia, particularly in older adults, with significant improvements in sleep quality, sleep efficiency, and reduced sleep latency compared to placebo. 1

Mechanism and Efficacy

Mirtazapine promotes sleep through:

• Blocking serotonin receptors
• Antagonizing histamine H1 receptors (causing sedation)
• Improving objective sleep parameters

Research evidence strongly supports mirtazapine's efficacy for insomnia:

• A 2025 randomized controlled trial in older adults showed significant reduction in insomnia severity compared to placebo (mean ISI score reduction of -6.5 vs -2.9 for placebo) 1
• Polysomnographic studies demonstrate that mirtazapine significantly improves:
  • Sleep latency
  • Sleep efficiency
  • Wake time after sleep onset
  • Total sleep time 2
• These improvements occur rapidly, with significant benefits observed after just 2 weeks of treatment 2

Dosing for Insomnia

• Starting dose: 7.5 mg at bedtime 3, 1
• Can be titrated up to 15-30 mg at bedtime if needed 3
• Lower doses (7.5-15 mg) are typically more sedating than higher doses due to the predominance of antihistamine effects at lower doses

Advantages Over Other Sleep Medications

• Not classified as a controlled substance (unlike benzodiazepines or Z-drugs)
• May have additional benefits for patients with comorbid depression or anxiety
• Low risk of dependence or withdrawal
• Improves both subjective and objective sleep parameters 4
• Can be used for long-term management of insomnia

Side Effects and Monitoring

Common side effects include:

• Increased appetite and weight gain (reported in 17% of patients) 5
• Daytime somnolence (54% of patients) 5
• Dry mouth
• Dizziness

Serious but rare concerns:

• QTc prolongation (dose-dependent)
• Angle-closure glaucoma in predisposed patients
• Hyponatremia
• Elevated cholesterol and triglycerides 5

Patient Selection Considerations

Mirtazapine may be particularly beneficial for:

1. Older adults with chronic insomnia 1
2. Patients with comorbid depression and insomnia 3, 4
3. Patients with poor appetite or weight loss
4. Those who have failed other sleep interventions

Caution or avoid in:

• Patients at risk for weight gain
• Those with narrow-angle glaucoma
• Patients with bipolar disorder (though risk of switch to mania is low with sleep-promoting doses) 6
• Patients taking other medications that prolong QTc interval 5

Monitoring Recommendations

• Assess sleep response within 1-2 weeks
• Monitor for excessive daytime sedation
• Track weight changes
• Consider discontinuation if no benefit after 4 weeks of adequate dosing

Conclusion

Mirtazapine represents an effective option for insomnia treatment with robust evidence supporting its use, particularly in older adults and those with comorbid depression. Its rapid onset of action and improvements in multiple sleep parameters make it a valuable alternative to traditional hypnotics.