From the FDA Drug Label
The FDA drug label does not answer the question.
From the Research
Hydroxizine should not be combined with xylazine in horses due to the potential for excessive sedation and respiratory depression. When administering hydroxizine to horses, it's generally recommended at doses of 0.5-1.0 mg/kg given orally or intramuscularly every 8-12 hours 1. Hydroxizine works primarily as an antihistamine and mild sedative by blocking H1 histamine receptors, making it useful for treating allergic conditions in horses. However, combining hydroxizine with CNS depressants like xylazine can cause adverse effects such as excessive sedation, incoordination, or changes in vital signs 2.
Some key points to consider when using hydroxizine in horses include:
- Monitoring for increased gastrointestinal irritation when using hydroxizine with NSAIDs such as phenylbutazone or flunixin meglumine
- Avoiding combination with certain antibiotics like erythromycin, which may increase the risk of cardiac arrhythmias
- Consulting with an equine veterinarian before combining hydroxizine with any medication, as individual horses may respond differently based on their health status, age, and concurrent conditions
- Observing the horse closely after administration for any adverse effects, as recent clinical trials have confirmed the efficacy of hydroxizine in generalized anxiety disorder, but also highlighted the importance of careful dosing and monitoring 3.
It's also important to note that xylazine has been associated with negative impacts on population health, particularly when used in combination with other drugs, and its use should be carefully considered and monitored 4.