A pyrazinoisoquinoline derivative with anthelminthic property. Praziquantel increases the permeability of the tegument of susceptible worms, resulting in an influx and increase in intra-tegumental calcium leading to rapid contractions and paralysis of the worm's musculature through a subsequent increase in levels of calcium in the sarcoplasmic reticulum. In addition, vacuolization of the tegumental syncytium and blebbing results in tegument disintegration, leads to antigen exposure and elicit host defense responses to the worm. The result is the formation of granulomas and phagocytosis.

An anthelmintic used in most schistosome and many cestode infestations.