Praziquantel is a pyrazinoisoquinolin derivative, with anthelmintic activity. ATC Vet Code: QP52AA01. The spectrum of action of praziquantel covers all the important species of cestodes in dogs and cats. It specifically includes all Taenia species occurring in dogs and cats, Multiceps multiceps, Joyeuxiella pasquali, Dipylidium caninum, Mesocestoides species, Echinococcus multilocularis and E. granulosus. Praziquantel is effective against all stages of development of these parasites occurring in the intestines of dogs and cats. Praziquantel impairs the normal tegument function of the parasite, making it permeable to excessive glucose loss and thereby more easily attacked by proteolytic enzymes. Because of this, whole tapeworms including the scolex are very rarely passed in the faeces following administration of the drug. Disintegrated and partially digested fragments may occasionally be seen in the faeces. Praziquantel is rapidly absorbed by the animal and metabolised by the liver. It is excreted, entirely as metabolites, in the urine and faeces.