The picture is divided in the situation before drug treatment (left) and during treatment (right). Antibodies of the immune system are not able to bind to the antigens on the surface of the worm. Paralyzers act via a cascade of reactions that eventually enable the antibodies to bind to the worm-antigens and allow the immune system to kill the worm. Praziquantel first induces a calcium influx through calcium-channels in the skin of the worm, which leads to quick muscle contractions. Because of the changes in permeability, the surface of the worm becomes irregular. At that point antibodies can reach the antigens on the surface from the host. Via antibody-mediated adherence of leukocytes the worm is killed.
Adverse effects of praziquantel are: transient abdominal discomfort and headache and dizziness. Because praziquantel is highly metabolized in the liver, drugs inducing hepatic P450 enzyme activity can reduce the action of praziquantel.
Another paralyzing drug, ivermectin paralyses parasites by selective binding to chloride channels in nerve and muscle cells, thereby increasing permeability. Ivermectin is used to treat onchocerciasis and strongyloidiasis.
Praziquantel is drug of choice for treating African trypanosomiasis.
Extra info: Praziquantel is only effective in taeniasis, hymenolepiasis and schistosomiasis. Trypanosomiasis is perhaps one of the most neglected diseases. There are far too few drugs to treat this disease despite >150000 death per year.
Praziquantel is drug of choice for treating schistosomiasis.