What is the recommended dose of mirtazapine (Remeron)?

Mirtazapine Dosing Recommendations

The recommended starting dose of mirtazapine is 15 mg once daily, administered orally in the evening prior to sleep, with titration up to a maximum of 45 mg per day based on clinical response. 1

Initial Dosing and Titration

• Start with 15 mg once daily, preferably in the evening before sleep 1
• 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 1
• Dose changes should not be made in intervals of less than 1-2 weeks to allow sufficient time for evaluation of response 1, 2
• The effective daily dosage range is 15-45 mg 3

Clinical Effects and Onset of Action

• Mirtazapine has a faster onset of action than some SSRIs, with improvements in depression symptoms potentially observed within 1-2 weeks 4
• Sleep disturbances and anxiety symptoms may improve within the first week of treatment 3
• Full therapeutic effect is typically observed after 4-6 weeks of treatment 3, 2
• Mirtazapine is particularly effective for patients with depression accompanied by sleep disturbances 5
• The drug promotes sleep, appetite, and weight gain, making it suitable for patients with depression accompanied by insomnia or weight loss 4

Pharmacokinetic Considerations

• Mirtazapine has an elimination half-life of 20-40 hours, enabling once-daily bedtime dosing 3
• The drug is extensively metabolized in the liver and primarily excreted in the urine 6
• Dosage adjustments may be needed in patients with hepatic or renal impairment 6

Special Populations and Drug Interactions

• In older patients and those with hepatic impairment, consider lower starting doses and slower titration 1, 6
• A decrease in dosage may be needed with concomitant use of strong CYP3A4 inhibitors (e.g., ketoconazole, clarithromycin) 1
• An increase in dosage may be needed with concomitant use of strong CYP3A inducers (e.g., carbamazepine, phenytoin, rifampin) 1
• A decrease in dosage may be needed with concomitant use of cimetidine 1

Common Side Effects

• Most common side effects include somnolence/sedation (23%), dry mouth (25%), increased appetite (11%), and weight gain (10%) 7, 3
• Sedation appears to be more pronounced at lower doses and may decrease at therapeutic doses 6
• Mirtazapine has minimal cardiovascular and anticholinergic effects 3
• Unlike SSRIs, mirtazapine has minimal sexual dysfunction side effects 3, 2

Discontinuation

• Gradually reduce the dosage rather than stopping abruptly to minimize discontinuation symptoms 1
• Adverse reactions may occur upon discontinuation or dose reduction 1

Monitoring

• Begin assessing patient status, therapeutic response, and adverse effects within 1-2 weeks of treatment initiation 4
• If the patient does not have an adequate response within 6-8 weeks, treatment modification is strongly recommended 4
• Monitor for rare but serious hematological changes such as agranulocytosis and neutropenia 7

Mirtazapine's unique mechanism of action as a noradrenergic and specific serotonergic antidepressant (NaSSA) makes it particularly effective for patients with depression accompanied by sleep disturbances and anxiety, with the added benefit of fewer sexual side effects compared to SSRIs.