Managing Bupropion-Induced Appetite Suppression
If you must continue bupropion 150 mg, add mirtazapine 15–30 mg at bedtime to counteract appetite suppression through its potent histamine H1-receptor antagonism, which directly stimulates appetite and promotes weight gain. 1
Understanding the Problem
Bupropion causes dose-related appetite suppression and weight loss through dopamine and norepinephrine reuptake inhibition. 2 In controlled trials:
- 14–19% of patients on bupropion sustained-release (300–400 mg/day) lost ≥5 lbs, compared to only 6% on placebo. 2
- Decreased appetite occurred in 4% of bupropion-treated patients versus 1% on placebo. 2
- The appetite-suppressing effect is mediated through central dopaminergic and noradrenergic pathways in the nucleus accumbens and hypothalamus. 3, 4
Primary Solution: Add Mirtazapine
Mirtazapine is the most effective pharmacologic option to restore appetite while continuing bupropion. 1
Dosing Strategy
- Start mirtazapine 15 mg at bedtime; titrate to 30 mg if needed based on appetite response and tolerability. 1
- The appetite-stimulating effect begins within the first weeks of therapy and persists throughout treatment. 1
Expected Outcomes
- In patients with depression and weight loss, mirtazapine 30 mg daily produced mean weight gain of 1.9 kg at 3 months and 2.1 kg at 6 months, with 80% of participants experiencing any weight gain. 1
- Mirtazapine causes the greatest appetite increase and weight gain among all antidepressants through histamine H1-receptor antagonism in the hypothalamus. 1
Mechanistic Rationale
Bupropion and mirtazapine have complementary mechanisms: bupropion enhances dopamine/norepinephrine (activating), while mirtazapine blocks histamine H1 and serotonin 5-HT2C receptors (appetite-stimulating and sedating). 1, 5 This combination addresses both depression and appetite suppression without pharmacologic antagonism. 5
Alternative Strategies
Switch Antidepressants
If mirtazapine is contraindicated or poorly tolerated:
- Switch to paroxetine (20–40 mg/day), which causes the greatest long-term weight gain among SSRIs. 1
- Paroxetine produces notable weight gain exceeding that of sertraline, fluoxetine, and venlafaxine. 1
- Avoid this switch if sexual dysfunction is a concern, as paroxetine has the highest rates of sexual side effects among all antidepressants. 1
Reduce or Discontinue Bupropion
- If the indication for bupropion is not compelling (e.g., smoking cessation completed, depression controlled), consider discontinuing it entirely. 6
- Bupropion's appetite-suppressing effect is dose-dependent; reducing from 150 mg to a lower dose may partially restore appetite, though this risks loss of therapeutic efficacy. 2
Appetite Stimulants Are NOT Recommended
Do not prescribe appetite stimulants (megestrol acetate, corticosteroids, dronabinol) for bupropion-induced appetite suppression in otherwise healthy patients. 7, 8
- Megestrol acetate and corticosteroids are indicated only for cancer cachexia, not medication side effects. 7, 8
- Megestrol acetate causes thromboembolic events, edema, and adrenal suppression. 7
- Corticosteroids lose efficacy with long-term use and are reserved for patients with life expectancy of weeks to months. 7
- Dronabinol has not been shown to have appetite-stimulating effects in controlled trials. 8
Common Pitfalls
Do not assume weight loss from bupropion is always harmful. In patients with overweight or obesity, bupropion's weight-reducing effect may be therapeutically beneficial. 9, 10, 11 The combination of naltrexone/bupropion is FDA-approved specifically for weight management. 10
Do not prescribe mirtazapine solely for weight gain in the absence of depression or another psychiatric indication. 1 Mirtazapine is appropriate here because the patient is already on an antidepressant (bupropion), suggesting an underlying mood disorder.
Recognize that bupropion's appetite suppression is a central mechanism, not a peripheral gastrointestinal side effect. 3, 4 Dietary counseling alone is unlikely to overcome this pharmacologic effect.
Monitor for excessive sedation when combining bupropion (activating) with mirtazapine (sedating). 1 The sedating effect of mirtazapine may counterbalance bupropion-induced insomnia, but some patients experience daytime somnolence.