Recommended Dosage and Treatment Plan for Mirtazapine in Major Depressive Disorder
The recommended treatment plan for mirtazapine in major depressive disorder begins with 15 mg once daily at bedtime, with gradual titration up to a maximum of 45 mg daily based on clinical response, with dose changes made at intervals of 1-2 weeks to allow sufficient time for evaluation. 1
Initial Dosing and Titration
- Start with 15 mg once daily, preferably in the evening prior to sleep 1
- If inadequate response occurs, increase the dose gradually up to a maximum of 45 mg per day 1
- Allow 1-2 weeks between dose adjustments to properly evaluate response 1
- Mirtazapine is particularly effective for patients with depression accompanied by sleep disturbances due to its sedative properties 2
Monitoring and Response Timeline
- Begin assessing patient status, therapeutic response, and adverse effects within 1-2 weeks of treatment initiation 3
- Most patients show initial improvement in symptoms within 2-4 weeks of starting treatment 4
- Sleep disturbances and anxiety symptoms may improve within the first week of treatment 4
- If the patient does not have an adequate response within 6-8 weeks, treatment modification is strongly recommended 3
Duration of Treatment
- Continue treatment for 4-9 months after a satisfactory response in patients with a first episode of major depressive disorder 3
- For patients who have had 2 or more episodes of depression, an even longer duration of therapy may be beneficial 3
Common Side Effects to Monitor
- Sedation/somnolence (most common side effect) 2
- Increased appetite and weight gain 2
- Dry mouth 3
- Constipation or diarrhea 2
- Minimal sexual dysfunction (advantage over many other antidepressants) 4
Special Considerations
- Mirtazapine has minimal cardiovascular and anticholinergic effects 4
- It has a unique mechanism of action as a noradrenergic and specific serotonergic antidepressant (NaSSA) 5
- The drug appears to be safe in overdose and has a very low propensity for inducing seizures 6
- Mirtazapine has a long half-life (20-40 hours) which enables once-daily bedtime dosing 4
Discontinuation
- Gradually reduce the dosage rather than stopping abruptly to minimize discontinuation symptoms 1
- Adverse reactions may occur upon discontinuation or dose reduction 1
Drug Interactions
- Screen for bipolar disorder prior to initiating treatment 1
- Allow at least 14 days between discontinuation of an MAOI and initiation of mirtazapine 1
- Dose adjustments may be needed with concomitant use of strong CYP3A inducers or inhibitors 1
Advantages Over Other Antidepressants
- Faster onset of action than some SSRIs (fluoxetine, paroxetine, sertraline) 3
- Lower rates of sexual dysfunction compared to many SSRIs 7
- Particularly beneficial for patients with depression accompanied by insomnia due to its sedative properties 7
Mirtazapine is a potent and well-tolerated antidepressant that promotes sleep, appetite, and weight gain, making it particularly suitable for patients with depression accompanied by insomnia or weight loss 3.