Antiparasitic drugs (ATH) are important tools widely used to maintain animal welfare. As parasites impart a great impact on animal health, these drugs are often essential for the expression of the full genetic potential of production. However, despite the initial success, after years of massive use of anthelminthic drugs , the increase in prevalence of resistant nematodes became a major problem. Anthelmintics are commonly used to treat parasitic worm infections not only in animals, but humans as well. Resistance to anthelmintics is thought to be present in several helminth species, yet it remains poorly studied. This books discusses topics such as the clinical pharmacology of anthelmintics; the uses in human and veterinary medicine; animal resistance to ATH; and the efficacy of Neem and Pawpaw products against Oesophahostomum spp infection in pigs.