Mirtazapine Dosing for Sleep

Guideline Recommendations

The American Academy of Family Physicians recommends a starting dose of 15mg once daily at bedtime, with an effective dosage range of 15-45mg daily, as 7.5mg is considered subtherapeutic 1
The American Academy of Sleep Medicine recommends mirtazapine as a sedating low-dose antidepressant option for insomnia, typically in the range of 7.5-30mg at bedtime 2
Multiple guidelines note that mirtazapine is "potent and well tolerated; promotes sleep, appetite, and weight gain" at the standard 7.5-30mg bedtime dosing range, without distinguishing enhanced sleep efficacy at the lowest dose 1

Pharmacokinetic studies demonstrate dose-proportional plasma concentrations: 15mg produces mean levels of 7.3±3.2 ng/mL, 30mg produces 18±7 ng/mL, and 45mg produces 28±12 ng/mL 1

Start with 7.5mg at bedtime as an initial trial dose, then increase to 15mg if inadequate response after 1-2 weeks, and potentially to 30mg or 45mg maximum if still inadequate at 6-8 weeks 1, 2, 3

In elderly or debilitated patients, lower starting doses are recommended, but this reflects general caution rather than enhanced efficacy 3
Mirtazapine has been shown safe in cardiovascular disease, even at high multiples of recommended doses 2, 3
Exercise caution in hepatic/renal impairment, as clearance may be reduced 2

Mirtazapine did not improve sleep apnea in multiple studies and may worsen OSA through weight gain 4, 5, 6
European Respiratory Journal guidelines state that drug therapy is not recommended as treatment for OSA, with mirtazapine having a grade B recommendation against use 5
The British Journal of Pharmacology notes that mirtazapine causes weight gain that can worsen OSA, despite one case report showing AHI decrease 6

If sedation is excessive, consider switching to trazodone, though it may increase arousals 4
Cognitive behavioral therapy for insomnia should be implemented as first-line non-pharmacologic treatment 2
Benzodiazepine receptor agonists or melatonin receptor agonists represent alternative pharmacologic options, though they carry risks of cognitive impairment and falls 2