Wow, the FDA should really be more strict about quality control with our drugs. It's pretty sad that it's ok to sell something as the equivalent of another medicine, when the "equivalent" doesn't work as well. It should be printed in a big warning box that the generic medicines have a different formula or different inactive ingredients than the original patent medication.
On the subject of the bad reactions to the generic Imuran, anyone who gets defectively made generic Imuran or any other defectively made medicine in general can go here
to report it to the FDA. There is no excuse for something like that and apparently the FDA takes it pretty seriously to get it gone or fixed.