Can mirtazapine (Remeron) cause drowsiness?

Mirtazapine and Drowsiness

Yes, mirtazapine commonly causes drowsiness and sedation, which is why it is typically administered at bedtime to help patients with sleep disturbances. 1, 2

Mechanism and Prevalence of Drowsiness

• Mirtazapine has a high affinity for histamine H1 receptors, which is primarily responsible for its sedative effects 3
• Drowsiness/sedation is one of the most frequent adverse reactions, reported in 23% of patients compared to 14% with placebo 4
• Excessive sedation occurs in approximately 19% of patients versus 5% with placebo 4
• Drowsiness is most pronounced during the first month of treatment, with the highest incidence density (58.1 per 1000 patient-months) occurring in the initial month 5

Clinical Implications

• The sedative effect is dose-dependent, with lower doses (7.5-15mg) typically producing more sedation than higher doses (30-45mg) due to the predominance of histamine blockade at lower doses 2, 3
• Mirtazapine is specifically recommended to be taken at bedtime to capitalize on its sedative properties for patients with insomnia 1
• The sedative effect is often therapeutic and intentionally utilized in patients with depression who have sleep disturbances 1
• While drowsiness is common initially, it tends to decrease over time despite increased doses of mirtazapine 4

Clinical Applications

• Mirtazapine is specifically recommended for patients who would benefit from its sedative properties:
  • Patients with depression and comorbid insomnia 1
  • Patients with cardiovascular disease who need sleep assistance 1
  • Patients who would benefit from appetite stimulation along with antidepressant effects 1

Safety Considerations

• Patients should be warned about the potential for drowsiness and advised not to drive, operate heavy machinery, or engage in activities requiring alertness until they know how mirtazapine affects them 2
• The FDA label specifically states: "Mirtazapine tablets can cause sleepiness or may affect your ability to make decisions, think clearly, or react quickly" 2
• Alcohol should be avoided during treatment with mirtazapine as it can enhance the sedative effects 2
• Elderly patients may be more sensitive to the sedative effects and should typically start with lower doses 1, 2

Dosing to Manage Drowsiness

• Initial dosing at 7.5mg at bedtime is recommended, especially in elderly or sensitive patients 1
• A fixed dosing regimen (rather than escalating doses) may provide better sleep benefits 6
• Most patients develop tolerance to the sedative effects over time, with drowsiness decreasing despite continued treatment 4
• If daytime drowsiness is problematic, consider:
  • Ensuring the medication is taken at bedtime 2
  • Adjusting the dose (sometimes higher doses may actually cause less sedation) 3
  • Evaluating for other contributing factors such as other medications or medical conditions 2

Common Pitfalls

• Combining mirtazapine with other sedating medications (especially benzodiazepines) can lead to excessive sedation and potentially dangerous respiratory depression 1
• Patients may misinterpret the initial sedation as a worsening of depression rather than a medication side effect 3
• The sedative effect may be beneficial for sleep but problematic for daytime functioning if the timing of administration is not optimized 2, 6
• Abrupt discontinuation should be avoided; gradual tapering over 10-14 days is recommended to minimize withdrawal symptoms 1

Mirtazapine's sedative properties make it a useful option for patients with depression who also have insomnia, but proper patient education about the expected drowsiness and appropriate timing of administration are essential for optimizing its therapeutic benefits while minimizing adverse effects.