title: Evaluation of a covered-rod silicone implant containing ivermectin for long-term prevention of heartworm infection in dogs.
abstract: OBJECTIVE
  To evaluate use of covered-rod (CR) silicone implants containing ivermectin for long-term prevention of infection with Dirofilaria immitisin dogs.
  
  
  METHODS
  145 adult male and female dogs.
  
  
  METHODS
  Dogs received implants of different sizes, and ivermectin concentrations and serum ivermectin concentrations were monitored for 16, 57, and 56 weeks, respectively, in 3 preclinical dose selection studies. Ability of implants to prevent infection with D immitis was evaluated in 2 further studies; dogs were challenged with 50 infective third-stage larvae 52 weeks after implant administration and necropsied 145 days after challenge, and the total number of adult heartworms was counted. A field study was then undertaken in which client-owned dogs received an implant and plasma samples were collected at intervals until week 52 for ivermectin analysis and heartworm antigen determination.
  
  
  RESULTS
  Use of the implants resulted in maintenance of an ivermectin concentration > or = 0.2 ng/mL for 12 months. In challenge studies, no treated dogs had adult heartworms, in contrast to untreated dogs, which all had adult heartworms at necropsy. In the field study, dogs treated with an implant had negative results of heartworm antigen testing for 12 months.
  
  
  CONCLUSIONS
  The CR silicone implant containing 7.3 mg of ivermectin was 100% effective in preventing experimental infection with D immitislarvae and resulted in negative results for heartworm antigen in a field trial. This product has the potential to alleviate poor owner compliance with monthly prevention regimens.
authors.affiliation: Smart Drug Systems Inc, Ste 102, 181 S Broad St, Pawcatuck, CT 06379, USA.
authors.forename: Craig P
authors.initials: CP
authors.lastname: Cunningham
authors.forename: Jenaay M
authors.initials: JM
authors.lastname: Brown
authors.forename: Glenn A
authors.initials: GA
authors.lastname: Jacobson
authors.forename: Malcolm R
authors.initials: MR
authors.lastname: Brandon
authors.forename: Serge R
authors.initials: SR
authors.lastname: Martinod
mesh_terms: D000818:Animals; D000871:Anthelmintics / Q000008:administration & dosage* / Q000097:blood; D000947:Antigens, Helminth / Q000097:blood; D004183:Dirofilaria immitis / Q000254:growth & development* / Q000276:immunology; D004184:Dirofilariasis / Q000097:blood / Q000469:parasitology / Q000517:prevention & control*; D004283:Dog Diseases / Q000097:blood / Q000469:parasitology* / Q000517:prevention & control*; D004285:Dogs; D004305:Dose-Response Relationship, Drug; D004343:Drug Implants; D005260:Female; D006321:Heart / Q000469:parasitology; D007559:Ivermectin / Q000008:administration & dosage* / Q000097:blood; D008168:Lung / Q000469:parasitology; D008297:Male; D012828:Silicones / Q000008:administration & dosage
chemical_list: D000871:Anthelmintics; D000947:Antigens, Helminth; D004343:Drug Implants; D012828:Silicones; D007559:Ivermectin