From the FDA Drug Label
The recommended starting dose of mirtazapine tablets is 15 mg once daily, administered orally, preferably in the evening prior to sleep. If patients do not have an adequate response to the initial 15 mg dose, increase the dose up to a maximum of 45 mg per day The mean mirtazapine dose for patients who completed these 4 studies ranged from 21 to 32 mg/day
The effective dose of mirtazapine for sedation in patients with depression or anxiety is 15 mg to 45 mg per day, with a typical starting dose of 15 mg once daily. The dose can be increased up to a maximum of 45 mg per day if patients do not have an adequate response to the initial dose. Key points to consider:
- Dose titration: Increase the dose in intervals of at least 1 to 2 weeks to allow sufficient time for evaluation of response to a given dose.
- Mean dose: The mean mirtazapine dose for patients who completed studies ranged from 21 to 32 mg/day. 1 1
From the Research
Mirtazapine is typically started at a low dose of 7.5-15 mg taken once daily at bedtime for sedation in patients with depression or anxiety, with 15 mg being the most common starting dose, as supported by the most recent study 2. The medication's unique pharmacology, which blocks histamine H1 receptors at lower doses, causes sedation.
- At these lower doses, mirtazapine tends to produce more sedation than higher doses.
- As the dose increases to 30-45 mg daily, the medication's noradrenergic effects become more prominent, which can actually reduce the sedative effects.
- Most patients experience sedative effects within the first few days of treatment. If sedation is the primary goal while also treating depression or anxiety, maintaining a lower dose of 15 mg at bedtime may be optimal, as noted in 3 and 4. The medication should be taken 1-2 hours before bedtime to maximize its sleep-inducing effects.
- Patients should be advised that morning grogginess may occur initially but often improves with continued use.
- Elderly patients or those with hepatic impairment should start at 7.5 mg due to slower drug metabolism, as mentioned in 5 and 6. The sedative effects of mirtazapine should not be combined with alcohol or other CNS depressants as this can cause excessive sedation. Key points to consider when prescribing mirtazapine for sedation include:
- Starting with a low dose and gradually increasing as needed
- Monitoring for morning grogginess and adjusting the dose or timing of administration accordingly
- Avoiding concomitant use with other CNS depressants
- Considering the patient's age, hepatic function, and other medical conditions when determining the initial dose and titration schedule.