Does Hydroxyzine Cause Weight Gain?
Weight gain is a documented side effect of hydroxyzine, occurring in approximately 12% of patients, which is only slightly higher than placebo (10%).
Evidence for Weight Gain
The most direct evidence comes from a controlled clinical trial examining hydroxyzine 50 mg daily for generalized anxiety disorder, where weight gain was reported in 12% of hydroxyzine-treated patients compared to 10% receiving placebo 1. While this difference is modest, it confirms that weight gain does occur with hydroxyzine use.
Clinical Context and Mechanism
Hydroxyzine is a first-generation antihistamine with significant anticholinergic properties 2. The mechanism for weight gain likely relates to:
- Antihistamine effects: H1 receptor blockade can increase appetite and alter metabolism 2
- Sedation: The pronounced sedative effects may reduce physical activity and energy expenditure 2
- Anticholinergic properties: These can contribute to metabolic changes 2
More Concerning Side Effects
While weight gain occurs, the more clinically significant concerns with hydroxyzine include 2:
- Sedation and performance impairment (28% vs 14% with placebo) 1
- Cognitive decline, particularly in elderly patients 2
- Driving impairment: Drivers taking first-generation antihistamines are 1.5 times more likely to be responsible for fatal automobile accidents 2
- Falls and fractures in older adults 2
Clinical Recommendations
When prescribing hydroxyzine, counsel patients that:
- Weight gain occurs in roughly 1 in 8 patients 1
- The effect is modest and comparable to placebo rates 1
- More significant concerns include sedation, cognitive impairment, and safety risks 2
- Second-generation antihistamines (cetirizine, fexofenadine) are generally preferred alternatives with lower risk profiles 2
Special caution is warranted in elderly patients due to increased sensitivity to psychomotor impairment, anticholinergic effects, and fall risk 2.