What is the dosing regimen for Mirtazapine (Remeron) for treating depression or anxiety symptoms?

Mirtazapine Dosing for Depression and Anxiety

Start mirtazapine at 15 mg once daily at bedtime, and if inadequate response occurs, increase up to a maximum of 45 mg daily, with dose changes made no more frequently than every 1-2 weeks. 1

Initial Dosing

• Begin with 15 mg once daily, administered in the evening prior to sleep 1
• This starting dose is supported by both FDA labeling and clinical guidelines 1, 2, 3
• The bedtime dosing takes advantage of mirtazapine's sedating properties, which can improve sleep disturbances often present in depression 4, 5

Dose Titration

• If patients do not respond adequately to 15 mg, increase the dose up to a maximum of 45 mg per day 1
• Wait at least 1-2 weeks between dose adjustments to allow sufficient time to evaluate response 1
• The effective dosage range is 15-45 mg daily 2, 6
• Dose changes should be gradual to assess therapeutic benefit at each level 1

Timeline for Response Assessment

• Begin assessing therapeutic response and adverse effects within 1-2 weeks of treatment initiation 4
• Sleep disturbances and anxiety symptoms may improve within the first week of treatment 2, 7
• Full antidepressant effect typically occurs within 2-4 weeks 2, 7
• If inadequate response occurs within 6-8 weeks, treatment modification is strongly recommended 4

Duration of Treatment

• Continue treatment for 4-9 months after satisfactory response in patients with a first episode of major depressive disorder 4, 5
• For patients with 2 or more episodes of depression, longer duration of therapy is beneficial 4, 5

Special Clinical Considerations

Mirtazapine is particularly well-suited for specific patient populations:

• Patients with depression and insomnia or sleep disturbances - mirtazapine promotes sleep effectively 4, 8, 5
• Patients with depression and poor appetite or weight loss - mirtazapine increases appetite and promotes weight gain 4, 5
• Patients with depression and anxiety symptoms - mirtazapine has beneficial anxiolytic effects 5, 3, 6

Common Pitfalls and Monitoring

Key adverse effects to anticipate:

• Sedation/somnolence - most common side effect, but beneficial for patients with insomnia 4, 2, 3
• Increased appetite and weight gain - can be significant and should be monitored, especially in weight-conscious patients 4, 5, 7
• Dry mouth - common but generally well-tolerated 4
• Constipation or diarrhea may occur 4

Important caveat: Paradoxically, sedation may be more pronounced at lower doses (below 15 mg), so starting at the recommended 15 mg dose rather than lower is appropriate 9

Drug Interactions Requiring Dose Adjustment

• With strong CYP3A inducers (carbamazepine, phenytoin, rifampin): increase mirtazapine dose 1
• With strong CYP3A4 inhibitors (ketoconazole, clarithromycin): decrease mirtazapine dose 1
• With cimetidine: decrease mirtazapine dose 1
• MAOI antidepressants: allow at least 14 days between discontinuing an MAOI and starting mirtazapine, or vice versa 1

Discontinuation

• Gradually taper the dose rather than stopping abruptly to minimize withdrawal symptoms 1

Advantages Over Other Antidepressants

• Faster onset of action than some SSRIs (fluoxetine, paroxetine, sertraline) 4
• Minimal cardiovascular and anticholinergic effects 2
• Essentially lacks serotonergic side effects such as gastrointestinal symptoms and sexual dysfunction 2, 7
• Once-daily dosing due to 20-40 hour elimination half-life 2, 9