this is a classic trick that the drug companys like to play. antara and tricor are both fenofibrate. but antara is "micronized" this means that it is ground into smaller particles. the idea is that more will get absorbed and faster. ie antara peaks in the blood in 4-6hr and tricor is 6-8hr. the other difference is the dose strength. of course in reality both are made so that two companies can profit from one drug.
you can read the drug info at the websites, within the first few lines you can see the differences and similarities.