When I read the decription of how it works I see the probable scenario as follows..
The attached Tapeworm is exposed to low concentrations initially and that causes it to become motile, as its sucker no longer works... This means it can no longer stay attached....
as the concentration of the prazi increases due to increased absorption and uptake into the fish... The medication causes a the rupture the tegument and compromise the parasites ability to maintain energy reserves... It dies and is passed out of the fish.
Thats at least how it sounds to me... Does anyone see a different interpretation here?
It seems to me that if the medicine works as rapidly as it is supposed to that the very first effect it has is to cause the worms to release their hold....after that the contractions occur as the concentration of the med increases.. Thats at least what the invitro experiments imply.
hth,
-al