When I first went on Synthroid (for my thyroid), I could not get a generic form. Although Synthroid is not nearly as expensive as anti-d's, it was nice to only have to pay for the Levoxyl (generic form) price. At the time I did a little research, and talked to my pharysist, and he told me that they were exactly the same thing.
The ingredients were exactly the same thing, and the same amounts and everything.
It is kind of like buying a store brand instead of the name brands when you shop for food. Tastes the same, looks somewhat similar (maybe a diff look), but saves on the $$$$$$$$$$$$$$$$$$$$$$$