Hi Ann,
Thank you for your question. The active ingredient in both Fosamax and aledronate is exactly the same. The only difference between the two may be the filler ingredients (such as which color dye is used). The generic companies perform a lot of testing on their products and must submit an extensive application to the FDA in order to prove that their product is just as effective as the brand name medication. You should not notice any difference, unless by chance you are allergic to one of the inactive ingredients in either product.
Best of luck,
Casey