Endocox powder from Jedd's is the drug toltrazuril, which actually kills coccidia rather than just setting it back until the chick's immune system grows enough to overcome it. Both Corid and sulfa drugs are coccidiostats which slow the coccidia down and set it back...which definitely has its place as we want the birds to develop resistance as they grow. But when there's a severe case or outbreak, I'd rather wipe it out and let the chickens recover and grow some, and that's where toltrazuril comes in as a coccidiocide. Dog breeders and some livestock raisers have been using toltrazuril for a long time and I've been surprised at how few chicken people seem to know about it....until I found that pigeon and other bird raisers do use it. It's extremely effective.