ABCB1-1 (MDR1-1) genotype is associated with adverse reactions in dogs treated with milbemycin oxime for generalized demodicosis

• Published in: Veterinary dermatology 2009-04, Vol.20 (2), p.111-114
• Main Authors: Barbet, Joy L, Snook, Tara, Gay, John M, Mealey, Katrina L
• Format: Article
• Language: English
• ISSN: 0959-4493; 1365-3164
• DOI: 10.1111/j.1365-3164.2008.00725.x

AbstractTwenty-two dogs diagnosed with generalized demodicosis were treated with milbemycin oxime (MO) because of poor response to previous therapies or because the dog was a breed known to be susceptible to ivermectin toxicosis. Fifteen of the 22 dogs were herding breeds. Doses of MO ranged from 1.0 to 2.2 mg kg-1 day-1 per os. Cheek swab samples were obtained in order to determine each dog's ABCB1 genotype. Adverse drug reactions were recorded for each dog by the owners and/or veterinarians. The ABCB1-1 genotype was significantly associated with the development of an adverse reaction (neurological toxicity) after treatment with MO. None of the 19 dogs with the wild-type ABCB1 allele experienced adverse reactions, whereas two dogs homozygous for the ABCB1-1 mutation developed ataxia. Assessing the ABCB1-1 genotype prior to MO administration may prevent neurological toxicity in these patients.