Cephalexin for dogs typically begins to work within 1 to 2 hours after administration, but noticeable improvement in symptoms may take 24 to 48 hours. This antibiotic is commonly prescribed to treat bacterial infections such as skin infections, urinary tract infections, and respiratory issues. The cephalexin for dogs works by stopping the growth of bacteria, allowing the immune system to heal the infection. It's essential to follow the veterinarian's dosage instructions and complete the full course, even if your dog seems better. Always consult your vet before starting or stopping any medication, including cephalexin for dogs.