Is penicillin the right antibiotic for my dog's ear infection?

Hello, and thank you for using Petco Pet Education Center, formerly Petcoach. The most important aspect of treating an ear infection is applying the appropriate medication (determined based on ear cytology, or looking at a sample of ear discharge on a microscope slide) directly into the ear canal as a topical treatment to the infection. Sometimes, particularly if the eardrum is ruptured, a dog may be put on an oral course of antibiotics and/or antifungals (depending on the type of infection), but penicillin would not be a usual antibiotic choice as it is unlikely to address the more common causes of ear infections. Therefore, injectable penicillin is not a typical component of treating an ear infection. I recommend you have Aerial seen by your primary veterinarian, and they can help guide you on an appropriate treatment of the infection; injectable antibiotics should never be used without the guidance of a veterinarian.