There are different types of drugs that target the different parasitic groups. The main type is that of the antihelmintics that targets all parasitic worms and these are broken down into the various subtypes such as antinematodes and anticestodes.
Early antiparasitics were ineffective, frequently toxic to patients, and difficult to administer due to the difficulty in distinguishing between the host and the parasite.
Between 1975 and 1999 only 13 of 1,300 new drugs were antiparasitics, which raised concerns that insufficient incentives existed to drive development of new treatments for diseases that disproportionately target low-income countries. This led to new public sector and public-private partnerships (PPPs), including investment by the Bill and Melinda Gates Foundation. Between 2000 and 2005, twenty new antiparasitic agents were developed or in development. In 2005, a new antimalarial cost approximately $300 million to develop with a 50% failure rate.