Lots of people react differently to generics. The generics are supposed to be the same thing as the name brand or each other and they are for the most part. But there can be some differences in non-active ingredients, fillers, etc. Those things can affect how the medication works for you. If the generic doesn't work either request the one that does or else ask the dr to write the script to be filled with the name brand medication. Otherwise the pharmacy will fill it with the generic they get at the lowest price. It's all about the bottom line. Good luck and God bless.
I am not a dr. My statements are based on years of experience and related education. Consult with the professional of your choice regarding matters of concern.