What is the recommended dosing for mirtazapine (Remeron) in a 68-year-old patient with depression?

Mirtazapine Dosing for a 68-Year-Old with Depression

Start mirtazapine at 15 mg once daily at bedtime, with potential titration up to 45 mg daily based on response, using the same dosing strategy as younger adults. 1

Initial Dosing Strategy

• Begin with 15 mg once daily at bedtime as the recommended starting dose for all adults, including older patients 1
• The evening administration timing takes advantage of mirtazapine's sedating properties, which can be beneficial for depression-associated sleep disturbances 2
• This 15 mg starting dose is appropriate for a 68-year-old patient, as the FDA labeling does not specify age-based dose reductions for mirtazapine 1

Dose Titration

• If inadequate response after 1-2 weeks, increase to 30 mg daily 1
• Maximum dose is 45 mg daily if the patient shows insufficient improvement at 30 mg 1
• Dose changes should not occur more frequently than every 1-2 weeks to allow adequate time to assess response 1
• The effective dosage range is 15-45 mg/day, with once-daily bedtime dosing enabled by the 20-40 hour elimination half-life 3, 4

Special Considerations for Older Adults

While the FDA label does not mandate lower starting doses for elderly patients 1, clinical guidelines for geriatric depression management suggest mirtazapine is a preferred agent for older adults due to its favorable tolerability profile 2. The drug is "potent and well tolerated" and "promotes sleep, appetite, and weight gain" 2, which can be advantageous in older patients with depression-related anorexia or insomnia.

Important caveat: Although some guidelines recommend starting at approximately 50% of adult doses in older adults for certain antidepressants 2, mirtazapine's FDA labeling does not specify this reduction 1. The 7.5 mg starting dose mentioned in some older guidelines 2 appears to be associated with increased sedation at subtherapeutic doses 4, making the standard 15 mg starting dose more appropriate.

Monitoring and Adjustment

• Assess response at 2-4 weeks, though sleep disturbances and anxiety may improve within the first week 3
• Monitor for common adverse effects including sedation (which paradoxically decreases at therapeutic doses ≥15 mg), increased appetite, and weight gain 3, 4
• The drug has minimal cardiovascular and anticholinergic effects compared to tricyclic antidepressants, making it safer in older adults 3, 4

Drug Interactions Requiring Dose Modification

• Decrease mirtazapine dose if co-administered with strong CYP3A4 inhibitors (ketoconazole, clarithromycin) or cimetidine 1
• Increase mirtazapine dose if co-administered with strong CYP3A inducers (carbamazepine, phenytoin, rifampin) 1
• Adjust doses back if the interacting medication is discontinued 1

Treatment Duration

• Continue for at least 4-12 months after first episode remission 2
• Taper gradually when discontinuing rather than stopping abruptly to minimize withdrawal symptoms 1