Hill's a/d is in the "prescription diet" line, but no it is not actually
a prescription item.  Hopefully your "ferret" vet can call or fax a
"prescription" to your local vet to solve your problem.  Hill's a/d is
a good food to use as a supplement (soup).  Plus if/when your ferrets
need surgery in the future they will already be used to a/d for the
recovery period.
 
Hope that helps,
Jerry Murray, DVM
[Posted in FML issue 4522]