Mirtazapine Dosing for Weight Gain and Appetite Stimulation
Start mirtazapine at 7.5-15 mg at bedtime and titrate up to a maximum of 30 mg at bedtime for weight gain purposes, as this dosing range optimally promotes appetite and weight gain. 1
Recommended Dosing Algorithm
Initial Dose:
- Begin with 7.5-15 mg at bedtime, as the lower end of the therapeutic range specifically promotes appetite and weight gain 1
- The 15 mg starting dose is most commonly recommended across guidelines 2
Titration Strategy:
- If inadequate response after 2-4 weeks, increase to 30 mg nightly 2
- Maximum dose for weight gain is 30 mg at bedtime 1
- Do not exceed 30 mg when the primary goal is weight gain, as higher doses (up to 45 mg used for depression) may paradoxically have less weight-promoting effects due to increased noradrenergic activity 1
Expected Weight Gain Outcomes
Clinical Evidence:
- In depression trials, 10% of patients experienced clinically significant weight gain versus 1% with placebo 1
- Appetite increased in 11% versus 2% with placebo 1
- A retrospective study using 30 mg daily showed mean weight gain of 1.9 kg at 3 months and 2.1 kg at 6 months, with approximately 80% of patients experiencing weight gain 2, 1
Monitoring Parameters
Weekly for First Month:
- Weight measurement 1
- Appetite and food intake assessment 1
- Sedation level (typically decreases over 1-2 weeks) 1
Monthly Thereafter:
- Continue weight and appetite monitoring 1
Common Side Effects at These Doses
- Sedation occurs in 19-23% versus 5-14% with placebo, which can be minimized by bedtime dosing 1
- Increased appetite and weight gain are the most common effects 3, 4
- Minimal cardiovascular, anticholinergic, gastrointestinal, or sexual dysfunction effects 3, 5
Critical Clinical Context: When to Use vs. Avoid
Appropriate Use:
- Patients with depression and concurrent appetite loss/weight loss, providing dual therapeutic benefit 2
- Gastroparesis with nausea, vomiting, and weight loss 2
- Functional dyspepsia with early satiety and weight loss 2
- End-stage disease when depression coexists 2
When NOT to Use:
- Do not use in dementia patients without concurrent depression, as side effects outweigh uncertain benefits 2, 1
- Avoid in patients where weight gain would be detrimental: obesity, cardiovascular disease, or metabolic syndrome 2
- Not recommended as a sole appetite stimulant without depression 2
Mechanism Explaining Dose-Response
The appetite-stimulating effect occurs primarily through histamine H1 receptor blockade, which is the most significant contributor to weight gain 2. Additionally, 5-HT2 and 5-HT3 receptor antagonism reduces nausea and early satiety, indirectly promoting food intake 2. The 7.5-30 mg range provides optimal antihistamine effects without excessive noradrenergic activation that occurs at higher doses 1.