Mirtazapine and Weight Gain
Yes, mirtazapine (Remeron) commonly causes weight gain as a side effect. In FDA labeling, increased appetite was reported in 17% of patients treated with mirtazapine compared to 2% for placebo, and weight gain of ≥7% of body weight was reported in 7.5% of mirtazapine-treated patients compared to 0% for placebo 1.
Mechanism and Evidence of Weight Gain
- Mirtazapine has been consistently associated with increased appetite and weight gain as side effects, which appear to be more common with this medication than with other antidepressants 1, 2
- In clinical studies, 8% of patients receiving mirtazapine discontinued treatment due to weight gain 1
- A prospective controlled study found that women taking mirtazapine for 6 weeks experienced significant increases in body weight (from 63.6 kg to 66.6 kg) and fat mass (from 20.9 kg to 22.1 kg) 3
- Leptin concentrations increased significantly during mirtazapine treatment, which may play a role in the weight gain mechanism 3
Comparative Weight Effects Among Antidepressants
- Mirtazapine has a higher risk of weight gain compared to many other antidepressants 4, 5
- Among antidepressants, bupropion is the only one consistently associated with weight loss rather than weight gain 4, 5
- SSRIs like fluoxetine and sertraline typically cause initial weight loss followed by weight neutrality with long-term use 5
- Tricyclic antidepressants, particularly amitriptyline, also have a high risk of weight gain 6
Clinical Applications
- Mirtazapine's weight gain effect has been studied as a potential therapeutic benefit in certain populations:
- In patients with Alzheimer's disease experiencing weight loss, mirtazapine (30 mg daily) led to weight gain in 77.3% of patients after 3 months (mean gain 1.93 kg) and in 82.3% after 6 months (mean gain 2.11 kg) 7
- Clinical guidelines note that mirtazapine could potentially play a beneficial role when dementia patients with weight loss and depression require antidepressant treatment 8
Metabolic Considerations
- Unlike some other medications that cause weight gain, mirtazapine treatment did not significantly affect glucose homeostasis in controlled studies 3
- However, a study in healthy men showed unfavorable changes in lipid metabolism after 7 days of mirtazapine treatment, including increased triglyceride levels and TG/HDL-C ratio, and decreased HDL-cholesterol 9
- These lipid changes occurred despite weight loss in the study participants, suggesting direct pharmacological effects on lipid metabolism independent of weight changes 9
Monitoring and Management
- Regular monitoring of weight is recommended during mirtazapine treatment 1
- For patients concerned about weight gain, consider:
Important Caveats
- Weight gain effects appear to be dose-dependent, with higher doses potentially causing more significant weight gain 2, 10
- Individual responses to mirtazapine vary, and not all patients will experience significant weight gain 1, 2
- The sedative effects of mirtazapine may contribute to reduced physical activity, potentially exacerbating weight gain 10