Can different brand drugs work differently?

dea, Yes you can have different effects from different brands so like with the Teva brand let the pharmacist know that you can't use the old one but Teva is working as well as the brand name. What it can be it is the same amount of active medication but the binders in the generic's can be different and cause you to have problems with it BECAUSE it may not break down in your system the same way as the brand name did. The best is when you try different ones because most insurance companies make us change sooner or later anyway. Alway keep track of the brands that you are having no problems with.And the brands you do have problems with so you know and check which you have before you leave the pharmacy. Or better yet request the brand that works the best when you reorder your prescription. This is not all in your head. Even with the same active medications, the different binders can affect you and also because you are using yours for seizures It would be good to call your Pharmacist and let them know about the problem with break thru seizures you were having of the old brand they gave you and that you do not want it again. good luck.