Anti-anxiety medications for dogs can have potential side effects, which vary depending on the specific medication used. Common side effects include drowsiness, lethargy, and decreased appetite. Some dogs may experience gastrointestinal issues such as vomiting or diarrhea. Behavioral changes, including increased aggression or hyperactivity, can also occur. In rare cases, dogs might show allergic reactions, presenting as swelling, itching, or difficulty breathing. It's essential to monitor your dog closely and report any adverse reactions to the veterinarian. Regular check-ups ensure the medication's efficacy and safety, allowing for adjustments as needed.