Armour Thyroid and Synthroid are both brand names. The difference is Armour is made from dessicated pig thyroid and Synthroid in the lab chemically. Armour has been around for years before Synthroid but doctors prefer the lab made chemicals and it is prescribed the most often. I know because I have been on both and have had this discussion with my doctors on why don't I change. There is a huge difference in symptom relief when I've tried and I suppose that would be the same for your client.
Unfortunately it looks like they'll have to pay for it, although I would think they should try for an exception.
Deb, with most Part D plans, if a beneficiary asks for an exception and it is granted, they cover it at a preferred brand copay, which is typically around $45 or so. Thus they're no better off going this route -- might as well procure it from the store at market price.