Bayer's Animal Health Division website states, "Praziquantel is active against cestodes (tapeworms). Praziquantel is absorbed, metabolized in the liver, and excreted in the bile. Upon entering the digestive tract from the bile, cestocidal activity is exhibited. Following exposure to praziquantel, the Tapeworm loses its ability to resist digestion by the mammalian host. Because of this, whole tapeworms, including the scolices (plural of "scolex"), are very rarely passed after administration of praziquantel. In many instances, only disintegrated and partially digested pieces of Tapeworms will be seen in the stool. The majority of Tapeworms are digested and are not found in the feces."
So for a person like me with no bile reaching the intestine it will only have action in the liver. That's fine as I'm suspecting liver flukes. But I'm real curious to see if it can work like Iodine and kill on contact.