Doxycycline is an antibiotic medication used in both dogs and cats to treat bacterial infections such as tick-borne diseases, respiratory infections, and urinary tract infections. It works by interfering with bacterial protein synthesis and killing the bacteria. Doxycycline can be administered orally or by injection, and the dosage may need to be adjusted based on the animal’s response and any potential side effects such as gastrointestinal upset or liver toxicity.