Praziquantel, a heterocyclic pyrazinoisoquinoline, is an important new anthelmintic effective against a broad range of cestodes and trematodes, many of which had been poorly re-sponsive to previously available agents. It is given in one to three doses. The drug is rapidly taken up by susceptible helminths, in which it appears to induce the loss of intra-cellular calcium, tetanic muscular contraction, and destruction of the tegument. The dif-ferential toxicity of this agent may be related to the inability of susceptible worms to metabolize the drug. Aside from transient, mild gastrointestinal symptoms, praziquantel appears remarkably free of side effects in humans. It is currently the drug of choice for the treatment of schistosomiasis, clonorchiasis, opisthorchiasis, and neurocysticercosis.
Good activity has been demonstrated against other common trematode and cestode infec-tions. Its high level of safety suggests that it may well play a significant role in worldwide mass therapy campaigns.