Starting Dose of Mirtazapine (Remeron) for Appetite Stimulation
For appetite stimulation in adults, start mirtazapine at 15 mg once daily at bedtime. 1, 2, 3
Dosing Rationale and Mechanism
- Mirtazapine's appetite-stimulating effects are mediated through histamine H1 receptor blockade and are present across the therapeutic dose range. 2, 4
- The standard starting dose of 15 mg once daily at bedtime is recommended for all indications, including when appetite stimulation is the primary goal. 2, 3, 5
- This dose provides both the appetite-enhancing effect and sedative properties that can benefit patients with concurrent sleep disturbances. 1, 4
Special Populations Requiring Lower Starting Doses
Older adults and sedation-sensitive patients should start at 7.5 mg once daily at bedtime (using a half-tablet of the 15 mg formulation), as they are more susceptible to sedation, falls, and orthostatic hypotension. 1
- Patients with hepatic impairment require a reduced starting dose of 7.5 mg due to decreased drug clearance. 5, 6
- The elderly metabolize mirtazapine more slowly, reaching steady-state concentrations in 6 days versus 4 days in younger adults. 4
Dose Titration Strategy
- If appetite stimulation is inadequate after 1-2 weeks at 15 mg, increase to 30 mg once daily at bedtime. 2, 5
- The effective dosage range is 15-45 mg daily, though appetite stimulation is typically achieved at lower doses (15-30 mg). 2, 3
- Dose adjustments should occur at intervals of not less than 1 week, as steady-state concentrations require approximately one week to achieve. 4, 6
Administration Timing
Always administer mirtazapine at bedtime to leverage its sedative properties and minimize daytime drowsiness. 1, 2, 3
- The elimination half-life of 20-40 hours enables once-daily bedtime dosing. 2, 6
- Bedtime administration is particularly appropriate when appetite stimulation is the goal, as increased appetite is a common side effect that patients can manage with evening dosing. 1, 2
Expected Onset and Side Effects
- Increased appetite and weight gain typically occur within the first 1-2 weeks of treatment. 2, 4
- Common side effects include sedation (which decreases at higher doses), increased appetite (11% vs 2% with placebo), and weight gain (10% vs 1% with placebo). 2, 5
- Unlike SSRIs, mirtazapine does not cause sexual dysfunction or gastrointestinal adverse effects. 4, 6
Clinical Pitfalls to Avoid
- Do not start at subtherapeutic doses below 15 mg in non-elderly patients, as this paradoxically increases sedation without providing full therapeutic benefit. 6
- Avoid combining mirtazapine with other sedating medications (benzodiazepines, opioids) without careful monitoring, as this increases risk of oversedation and respiratory depression. 1
- Monitor for metabolic effects including weight gain, diabetes, and dyslipidemia with long-term use (beyond 4-6 weeks). 1