Praziquantel parasite drug. Computer model of a molecule of the drug praziquantel. Atoms are represented as spheres and are colour-coded; carbon (pink), hydrogen (white), nitrogen (yellow) and oxygen (blue). Praziquantel belongs to a class of drugs known as anthelmintics that are used to treat parasitic worm infections, such as schistosomiasis and tapeworms. It works by paralysing the worm's muscles.