When can I increase the dose of Remeron (mirtazapine) for an inpatient currently on 15 mg?

Increasing Remeron (Mirtazapine) Dosage for Inpatient

Mirtazapine dose can be increased after 1-2 weeks on the current dose, as this interval allows sufficient time to evaluate response to the current dose. 1

Dosing Guidelines for Mirtazapine

• The recommended starting dose is 15 mg once daily, administered orally in the evening prior to sleep 1
• Dose increases should not be made in intervals of less than 1-2 weeks to allow sufficient time for evaluation of response to the current dose 1
• The dose can be gradually increased up to a maximum of 45 mg per day if patients do not have an adequate response to the initial dose 1
• Mirtazapine is potent and well-tolerated; it promotes sleep, appetite, and weight gain 2

Monitoring During Dose Adjustment

• Monitor for sedation, which is one of the most common side effects (23% vs 14% in placebo) 3
• Assess for dry mouth (25% vs 16%), increased appetite (11% vs 2%), and weight gain (10% vs 1%) which occur significantly more frequently with mirtazapine than with placebo 3
• Be aware that increased sedation is often related to subtherapeutic dosages and may be reported in substantially fewer patients when the drug is used in appropriate dosages (≥15 mg as a single evening dose) 4
• Evaluate for improvement in sleep disturbances and anxiety symptoms, which may improve in the first week of treatment, while full antidepressant effect typically takes 2-4 weeks 5

Special Considerations for Inpatients

• For inpatients, closer monitoring is possible, allowing for more confident dose adjustments at the minimum 1-week interval 1
• Mirtazapine shows linear pharmacokinetics over a dose range of 15 to 80 mg, with steady state reached in 4-6 days 6
• The elimination half-life of mirtazapine ranges from 20-40 hours, supporting once-daily dosing 6
• With therapeutic dosages of mirtazapine (15-45 mg/day), plasma concentrations typically range from 5-100 μg/L 6

Drug Interactions to Consider Before Increasing Dose

• A decrease in mirtazapine dosage may be needed with concomitant use of strong CYP3A4 inhibitors (e.g., ketoconazole, clarithromycin) 1
• An increase in mirtazapine dosage may be needed with concomitant strong CYP3A inducers (e.g., carbamazepine, phenytoin, rifampin) 1
• Cimetidine may require mirtazapine dose adjustment, as it can affect the drug's metabolism 1
• At least 14 days must elapse between discontinuation of an MAOI antidepressant and initiation of mirtazapine 1

Clinical Pearls

• Mirtazapine has minimal cardiovascular and anticholinergic effects, and essentially lacks serotonergic side effects such as gastrointestinal symptoms, insomnia, and sexual dysfunction 5
• Early onset of antidepressant action has been observed in some studies, with significant reductions in depression rating scale scores noted as early as 1 week after starting treatment 4
• Mirtazapine's beneficial effects on anxiety and sleep disturbances associated with depression may reduce the need for concomitant anxiolytic and hypnotic medication 4
• The drug appears to be safe in overdose with minimal cardiovascular or respiratory effects 5