Thank you for your question. My name is***** I have been a small animal veterinarian for 14 years and I'd like to help with our question.
Isaderm is combination steroid/antibiotic cream so it requires a prescription. In order to issue a prescription most regions require a veterinarian for have examined your dog within the last year. If your local vet has seen Peanut it the last year, you can call and ask for a prescription for the cream and then you can mail that prescriptions to the online pet supply places and they will fill it for you. Sometimes that is all a big hassle and people end up deciding to just get it from the local vet. But it would start with a call to your local vet requesting the prescription.
I hope that help, but if you have more questions please let me know.