How to adjust the regimen if a patient on mirtazapine (Remeron) 7.5 mg at bedtime has a lack of appetite?

Mirtazapine Dosage Adjustment for Patients with Poor Appetite

For a patient on mirtazapine 7.5 mg at bedtime who has no appetite, you should increase the dose to 15-30 mg at bedtime to optimize appetite stimulation effects. 1

Mechanism of Action and Appetite Effects

Mirtazapine works through a unique mechanism as a tetracyclic antidepressant that:

• Blocks presynaptic alpha-2 adrenergic receptors
• Antagonizes postsynaptic 5-HT2 and 5-HT3 receptors
• Increases both noradrenergic and serotonergic neurotransmission 2, 3

The current 7.5 mg dose is suboptimal for appetite stimulation. While this low dose is often used for sleep/insomnia effects, higher doses (15-30 mg) are more effective for appetite stimulation 1.

Dosage Adjustment Algorithm

1. Initial adjustment: Increase from 7.5 mg to 15 mg at bedtime

   • This is the recommended starting dose for appetite stimulation 1
   • Allow 1-2 weeks to assess response

2. If inadequate response after 2 weeks: Consider increasing to 30 mg at bedtime

   • The 15-30 mg range is most effective for appetite stimulation 1
   • Higher doses may provide better appetite stimulation while maintaining sedative effects

3. Maximum dose: Do not exceed 45 mg daily (rarely needed for appetite effects)

Monitoring Parameters

• Appetite improvement: Should be noticeable within 1-2 weeks
• Weight: Monitor for appropriate weight gain (goal is non-fluid weight gain)
• Sedation: May increase with higher doses
• Other side effects: Dry mouth, dizziness, constipation

Expected Benefits

Mirtazapine has been shown to:

• Increase appetite in 48% of hospitalized patients 4
• Produce weight gain in 77.3% of patients after 3 months (mean gain 1.93 kg) 5
• Improve meal intake by approximately 17% in inpatient settings 4

Important Considerations

• Timing: Administer at bedtime to minimize daytime sedation
• Sedation effects: Will likely increase with higher doses, which can be beneficial for patients with insomnia but problematic for those with daytime functioning concerns
• Weight monitoring: Regular weight checks are essential to ensure appropriate response
• Medication interactions: Use caution when combining with other CNS depressants

Common Pitfalls to Avoid

1. Maintaining subtherapeutic dosing: The 7.5 mg dose is primarily effective for sleep but suboptimal for appetite stimulation
2. Inadequate duration of trial: Allow at least 2-4 weeks at each dose level before determining efficacy
3. Failure to monitor weight: Weight should be monitored regularly to assess effectiveness
4. Overlooking sedation effects: Higher doses may cause excessive daytime sedation in some patients

Mirtazapine is recognized in guidelines as an effective option for both insomnia and appetite stimulation, with the National Comprehensive Cancer Network specifically recommending doses of 7.5-30 mg for sleep disturbances 6, and higher doses (15-30 mg) being more effective for appetite stimulation 1.