I.C.
Not all medicines are tested in people under 18 years or even 12 years of age. It takes a lot more time and money to do testings to get medications to pass FDA requirements for use in children under 6. Therefore, most medications are only tested in adults (used to be mostly men). Most drug companies get a medication's first phase testings done only in adults and get FDA approval so they can market the drug and start making money. If the drug has a market for the younger people, then they do further testings in the younger populations if that is profitable. Anyway, my point is your ENT and pharmarcist are not ignorants or irresponsible. They most likely are familiar with the medication and have prescribed the medicine to patients of different ages before. If you are worried, you should call your ENT to clarify and not jumped to conclusion that someone has made a mistake with your son's medication.
In terms of itcy ears, it could be water logged in the ear wax and making him itchy or dry skin conditions like eczema, since you said his ears are red, scaly and itchy. Have you tried hydrocortisone cream for the outside skin or hydrocortisone drops for the ear canals? What did your pediatrician think? ENT may not be an expert on skin conditions even if it involves the ears. If none of the above help, you might want to take him to a dermatologist for further evaluation.