My Insurance Company Has Listed My Current Medication, Delzicol, As

My insurance company has listed my current medication, Delzicol, as a non-preferred drug. However, the letter that they sent me states that I would be allowed to continue my medication with preauthorization from my gastroenterologist. My physician tried to authorize my prescription, but the insurance company insists that she can't. They offer the following alternatives: balsalazide disodium, sulfasalazine, sulfazine ec, and lialda. Are any of these viable alternatives?