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This is the only currently used drug in the pyrazinoisoquinolines. It has unsurpassed activity against cestodes and has activity against some trematodes, these include schistosomes but not the liver flukes.
It works by causing an influx of Ca2+ across the parasite tegument. This results in muscular spasms and the cestodes loose their position in the intestine and are moved away by peristalsis. This leads to the animals body attacking the cestodes weakened tegumental defence with antibodies, immune cells and lytic enzymes. The dead tapeworm is therefore mostly digested by the time it arrives in the faeces. Owners of pets with tapeworms often feel that this drug doesn't work as they don't see any passed tapeworms. Where in fact the drug has worked but has left no visible evidence to the owner of its working.