well they are totally different meds. aspirin and plavix both are anti platlets meds. aggrenox is a capsule and in it is a 25mg aspirin plus a vaso-dilator. so you get (usually take aggrenox 2 times a day) 50mg of aspirin plus the vaso-dilator. i have taken all of this and it is just a different combo to try. i am assuming you are still having symptons and that is why the switch.
just a note here, aggrenox can cause some wicked headaches the first two weeks of taking it as it is a vaso-dilator and the vessels in your head have to get used to it. it will go away i promise.
janet