we have used it from our doctor and from the pet store, it all seems to be the same stuff. We started with 300mg, then the Doc pushed it up to 1500 mg.
My wife felt the worms flipping around about 12 hours after taking it. But, it took a month for everything to flush out. We also took Ivermectin and Albendazole. The three work well together, but on different types of parasites.