Milbemycin is the active ingredient in both Interceptor and Sentinel. Sentinel is Interceptor with a second medication called lufeneron (which is an insect growth regulator) added to it. The lufeneron is a flea birth control for all practical purposes. The products are made in the same plant by Pfizer, and will be unavaible for the forseable furture. There was issues with several human OTC products packaging that were made in that plant and it is closed. That is the only plant Pfizer makes those drugs at so until it is back it will be very hard to get as backstock for those drugs has been used up.
Praziquantel is a deworming medication used in both animals and people. It mainly targets intestinal worms like tape worm, round worm etc.