title: Titration of subcutaneously administered eprinomectin against mature and immature nematodes in cattle.
abstract: Eprinomectin has been approved for use as a topically applied endectocide for beef and dairy cattle. To determine if eprinomectin has utility as an injectable anthelmintic, it was titrated at 0.05, 0.1, and 0.2 mg/kg s.c. against adult (Trial 1) and at 0.05, 0.1, 0.14, and 0.2 mg/kg s.c. against immature (Trial 2) stages of lung and gastrointestinal nematodes in cattle. In Trial 1, every dose of subcutaneously delivered eprinomectin showed maximal or near-maximal (> or = 99%) efficacy against Haemonchus placei, Ostertagia ostertagi, Trichostrongylus axei, T colubriformis, Cooperia punctata, Nematodirus helvetianus, Oesophagostomum radiatum, and Dictyocaulus viviparus. Adult C. oncophora was the only exception. However, even against this species, the lowest dose of 0.05 mg/kg showed 93% efficacy, and the efficacious dose necessary to kill 95% (ED95) of adults was 0.056 mg/kg. In Trial 2, every dose of subcutaneously delivered eprinomectin showed maximal or near-maximal (> or = 99%) efficacy against the immature stages of all of the above species of endoparasites. As a result, ED95 values could not be calculated. Consequently, the exquisite potency against endoparasites through parenteral administration suggests that eprinomectin may also have potential utility as an injectable product for cattle.
authors.affiliation: Merck Research Laboratories, Merck & Co., Inc., Rahway, New Jersey 07065, USA. wesley_shoop@merck.com
authors.forename: W
authors.initials: W
authors.lastname: Shoop
authors.forename: B
authors.initials: B
authors.lastname: Michael
authors.forename: J
authors.initials: J
authors.lastname: Egerton
authors.forename: H
authors.initials: H
authors.lastname: Mrozik
authors.forename: M
authors.initials: M
authors.lastname: Fisher
mesh_terms: D000367:Age Factors; D000818:Animals; D000871:Anthelmintics / Q000008:administration & dosage*; D002417:Cattle; D002418:Cattle Diseases / Q000188:drug therapy* / Q000469:parasitology; D004305:Dose-Response Relationship, Drug; D007279:Injections, Subcutaneous; D007559:Ivermectin / Q000008:administration & dosage* / Q000031:analogs & derivatives*; D008297:Male; D009348:Nematoda / Q000254:growth & development; D009349:Nematode Infections / Q000188:drug therapy / Q000662:veterinary*
chemical_list: D000871:Anthelmintics; D007559:Ivermectin; C101434:eprinomectin