title: Pharmacokinetics, efficacy, and adverse effects of selamectin following topical administration in flea-infested rabbits.
abstract: OBJECTIVE
  To determine pharmacokinetics, efficacy, and adverse effects of topically administered selamectin in flea-infested rabbits.
  
  
  METHODS
  18 healthy 5-month-old New Zealand White rabbits.
  
  
  METHODS
  On day 0, rabbits (n = 6/group) received topically applied selamectin at doses of 10 or 20 mg/kg or received no treatment. Each rabbit was infested with 50 fleas (Ctenocephalides felis) on days -1, 7, and 14. Live and dead flea counts were performed on days 2, 9, and 16, and treatment efficacy was calculated. Blood samples were collected prior to drug administration and at 6 and 12 hours and 1, 2, 3, 5, 7, 10, 14, 21, and 28 days after treatment for determination of plasma selamectin concentrations via high-performance liquid chromatography with mass spectrometry. Pharmacokinetic parameters were determined.
  
  
  RESULTS
  On day 2, efficacy of selamectin against flea populations of rabbits in the 10 and 20 mg/kg treatment groups was 91.3% and 97.1%, respectively, but by day 9, these values decreased to 37.7% and 74.2%, respectively. Mean terminal half-life and maximum plasma concentrations of selamectin were 0.93 days and 91.7 ng/mL, respectively, for rabbits in the 10 mg/kg group and 0.97 days and 304.2 ng/mL, respectively, for rabbits in the 20 mg/kg group. No adverse effects were detected.
  
  
  CONCLUSIONS
  Selamectin was rapidly absorbed transdermally and was rapidly eliminated in rabbits. Results suggested that topical administration at a dosage of 20 mg/kg every 7 days is efficacious for treatment of flea infestation in rabbits. Further studies are needed to assess long-term safety in rabbits following repeated applications.
authors.affiliation: Department of Clinical Sciences, College of Veterinary Medicine, Kansas State University, Manhattan, KS 66506, USA.
authors.forename: James W
authors.initials: JW
authors.lastname: Carpenter
authors.forename: Michael W
authors.initials: MW
authors.lastname: Dryden
authors.forename: Butch
authors.initials: B
authors.lastname: Kukanich
mesh_terms: D000287:Administration, Topical; D000818:Animals; D000977:Antiparasitic Agents / Q000008:administration & dosage / Q000097:blood / Q000493:pharmacokinetics / Q000627:therapeutic use; D019540:Area Under Curve; D004478:Ectoparasitic Infestations / Q000188:drug therapy / Q000662:veterinary*; D005260:Female; D006207:Half-Life; D007559:Ivermectin / Q000008:administration & dosage / Q000031:analogs & derivatives* / Q000097:blood / Q000493:pharmacokinetics / Q000627:therapeutic use; D008297:Male; D011817:Rabbits; D005423:Siphonaptera
chemical_list: D000977:Antiparasitic Agents; D007559:Ivermectin; C414354:selamectin