I have a question about substitution of Levoxyl (King Pharmaceuticals) for a generic. I looked up in the Orange Book for AB equivalence. Under TE code it says AB1, AB3. Then I searched for levothyroxine. Do the generics have to have both AB1 & AB3 or just one of them to be able to be substituted? i.e. one by Genpharm says AB2, AB3...is this acceptable??