From the Guidelines
The recommended dose of mirtazapine is 15 mg once daily, with a maximum dose of 45 mg once daily, according to response to treatment and tolerability. This dosage recommendation is based on the most recent and highest quality study available, which provides a clear guideline for the use of mirtazapine in clinical practice 1. The starting dose of 15 mg once daily is intended to minimize side effects, with the option to increase the dose as needed and as tolerated by the patient.
Key points to consider when prescribing mirtazapine include:
- Starting dose: 15 mg once daily
- Dose titration: according to response to treatment and tolerability
- Maximum dose: 45 mg once daily
- Common side effects: sleep disorders, constipation or diarrhea, anxiety, increased appetite and weight gain, nausea, headache, fatigue
It is essential to monitor patients for these potential side effects and adjust the dose accordingly, with the goal of achieving the best possible therapeutic effect while minimizing adverse effects 1. By following this dosage guideline, clinicians can effectively utilize mirtazapine in the treatment of various conditions, including chronic gastrointestinal pain in disorders of gut-brain interaction.
From the FDA Drug Label
- 1 Recommended Dosage 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 recommended dose for mirtazapine is:
- Starting dose: 15 mg once daily
- Maximum dose: 45 mg per day Dose changes should not be made in intervals of less than 1 to 2 weeks to allow sufficient time for evaluation of response to a given dose 2
From the Research
Mirtazapine Dosage
- The recommended initial dosage of mirtazapine is 15 mg once/day at bedtime, with an effective daily dosage range of 15-45 mg 3.
- The recommended starting dosage of mirtazapine is 15 mg/day for 4 days, then 30 mg/day for 10 days. If effective, the drug should be continued unchanged at this dosage or, in patients assessed as insufficiently improved, the daily dosage may be further increased to 45 mg/day 4.
- The recommended starting dosage is 15 mg/day administered in a single dose at bedtime 5.
- In patients with hepatic or renal insufficiency, careful dosage titration as well as regular and close monitoring for adverse events is recommended 4.
- For frail, elderly patients with underlying chronic conditions, it might be more adequate to start mirtazapine therapy at a lower dose (<15 mg/d) 6.
Dosage Considerations
- Mirtazapine has an elimination half-life of 20-40 hours, enabling once-daily bedtime dosing 3.
- The mean elimination half-life of mirtazapine is approximately 22 hours, making it suitable for once-daily administration 4.
- Mirtazapine is extensively metabolised in the liver; up to 85% of the drug is eliminated in the urine (up to 4% as unchanged drug) and the remaining 15% is eliminated in the faeces 4.