title: Effects of treatment with aspirin or aspirin/dipyridamole combination in heartworm-negative, heartworm-infected, and embolized heartworm-infected dogs.
abstract: To determine the drug dose required to inhibit platelet reactivity by at least 50%, 2 drug regimens were evaluated in heartworm-negative, heartworm-infected, and heartworm-infected dogs embolized with dead heartworms. Aspirin, or a combination of aspirin and dipyridamole, were administered to 2 groups of Beagles (n = 5 each) for 5 to 9 days; a third group of 5 Beagles served as nontreated controls. For heartworm-negative dogs, mean (+/- SD) aspirin dosage that inhibited collagen-induced platelet reactivity by at least 50% was 6 (+/- 2) mg/kg of body weight given once daily. The aspirin/diphridamole combination dosage was 1 mg of each drug/kg given every 12 hours. All dogs (n = 15) were implanted with 7 adult heartworms each and remedicated (or not treated) beginning at 21 days after heartworm implantation. In heartworm-infected dogs, mean aspirin dosage required to inhibit collagen-induced platelet reactivity greater than or equal to 50% was 10 (+/- 6) mg/kg. Mean dosage of aspirin/dipyridamole combination was 1.6 +/- (0.5) mg of each drug/kg given every 12 hours. When platelet reactivity in response to collagen was determined to be inhibited by at least 50% in all medicated dogs, each dog (n = 15) was embolized with 7 dead adult heartworms to mimic heartworm adulticidal treatment. Platelet reactivity was monitored for 21 days after treatment, and drug dose was adjusted to maintain platelet inhibition by at least 50%. In embolized dogs, mean aspirin dosage was 17 (+/- 14) mg/kg given once daily. Mean dosage of the aspirin/dipyridamole combination was 2.8 (+/- 1.3) mg of each drug/kg given every 12 hours. All dogs (n = 15) were euthanatized 21 days after heartworm embolization. Each lung lobe was evaluated for severity of lesions and presence of organized or fibrinous thrombi. Lesion severity in the aspirin- and aspirin/dipyridamole-treated dogs was not significantly different from that in control dogs.
authors.affiliation: Department of Pathobiology, College of Veterinary Medicine, Auburn University, AL 36849-5519.
authors.forename: M K
authors.initials: MK
authors.lastname: Boudreaux
authors.forename: A R
authors.initials: AR
authors.lastname: Dillon
authors.forename: W R
authors.initials: WR
authors.lastname: Ravis
authors.forename: E A
authors.initials: EA
authors.lastname: Sartin
authors.forename: J S
authors.initials: JS
authors.lastname: Spano
mesh_terms: D000244:Adenosine Diphosphate / Q000494:pharmacology; D000818:Animals; D001241:Aspirin / Q000494:pharmacology / Q000627:therapeutic use*; D001792:Blood Platelets / Q000187:drug effects* / Q000502:physiology; D003094:Collagen / Q000494:pharmacology; D004176:Dipyridamole / Q000494:pharmacology / Q000627:therapeutic use*; D004184:Dirofilariasis / Q000097:blood / Q000188:drug therapy / Q000662:veterinary*; D004283:Dog Diseases / Q000097:blood / Q000188:drug therapy*; D004285:Dogs; D004359:Drug Therapy, Combination; D004617:Embolism / Q000097:blood / Q000188:drug therapy / Q000662:veterinary*; D008168:Lung / Q000473:pathology; D010974:Platelet Aggregation / Q000187:drug effects; D010976:Platelet Count / Q000662:veterinary; D012701:Serotonin / Q000378:metabolism
chemical_list: D012701:Serotonin; D000244:Adenosine Diphosphate; D004176:Dipyridamole; D003094:Collagen; D001241:Aspirin