First, understand what type of external ear infection your dog has before buying any suitable non irritating solutions for the treatment. For bacterial infections, you can use any of the antibiotics prescribed by the vet, such as amoxicillin, cephalexin, or gentamicin sulfate USP. Antifungal medications like ketoconazole or clotrimazole are used to treat yeast infections. Mite infestations require ivermectin or selamectin spot-on treatments.