{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,7,11]],"date-time":"2026-07-11T01:13:12Z","timestamp":1783732392079,"version":"3.55.0"},"reference-count":19,"publisher":"American Animal Hospital Association","issue":"3","content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":[],"published-print":{"date-parts":[[2026,5,1]]},"abstract":"<jats:title>ABSTRACT<\/jats:title>\n                  <jats:p>A 5 yr old female spayed Australian shepherd dog with a prior diagnosis of atopy presented for increased pruritus despite immunotherapy. The dog had a history of seizures well controlled by levetiracetam and was genotyped as MDR1 mutant\/normal. Ilunocitinib, indicated for controlling pruritus in dogs, was considered. Because the label indicates ilunocitinib can cause cytopenias, a complete blood count (CBC) was performed before initiating treatment. Neutrophils, platelets, and red blood cell numbers were all within reference ranges, so treatment with ilunocitinib was initiated. At a 1 mo follow-up appointment, the dog was bright, alert, and responsive with an improved Pruritus Visual Analog Scale score. A CBC indicated pancytopenia. Ilunocitinib was discontinued and a CBC was repeated after 7 days, indicating resolution of neutropenia and thrombocytopenia, but persisting anemia. One month after discontinuing ilunocitinib, all cytopenias had resolved. Because of the dog\u2019s MDR1 genotype, the status of ilunocitinib as a canine P-glycoprotein substrate was assessed. Ilunocitinib was identified as a canine P-glycoprotein substrate. Blunted P-glycoprotein\u2013mediated biliary excretion of ilunocitinib likely resulted in accumulation and a relative overdose. Enhanced penetration of ilunocitinib into hematopoietic stem cells lacking P-glycoprotein expression may have also contributed to dysregulated hematopoiesis. Ilunocitinib should be used cautiously in dogs with P-glycoprotein deficiency.<\/jats:p>","DOI":"10.5326\/jaaha-ms-7552","type":"journal-article","created":{"date-parts":[[2026,4,22]],"date-time":"2026-04-22T02:17:25Z","timestamp":1776824245000},"page":"127-130","source":"Crossref","is-referenced-by-count":0,"title":["Ilunocitinib-Induced Pancytopenia in an Australian Shepherd Dog with the MDR1 Mutation"],"prefix":"10.5326","volume":"62","author":[{"given":"Katrina L.","family":"Mealey","sequence":"first","affiliation":[{"name":"From the Program in Individualized Medicine, College of Veterinary Medicine, Washington State University, Pullman, WA (K.L.M.); and"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Mary","family":"McFillen","sequence":"additional","affiliation":[{"name":"Department of Community Practice, Veterinary Health Center, College of Veterinary Medicine, University of Missouri, Columbia, MO (M.F., A.H.)."}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Alisa","family":"Hutchison","sequence":"additional","affiliation":[{"name":"Department of Community Practice, Veterinary Health Center, College of Veterinary Medicine, University of Missouri, Columbia, MO (M.F., A.H.)."}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"3280","reference":[{"issue":"1","key":"i1547-3317-62-3-127-b1","series-title":"J Vet Pharmacol Ther","first-page":"7","article-title":"Pharmacokinetics of ilunocitinib, a New Janus kinase inhibitor in dogs","volume":"49","author":"Boerngen","year":"2026","unstructured":"Boerngen K, Patel Y, Pittorino M,  Pharmacokinetics of ilunocitinib, a New Janus kinase inhibitor in dogs. J Vet Pharmacol Ther 2026;49(1):7\u201316."},{"issue":"10","key":"i1547-3317-62-3-127-b2","series-title":"Allergy","first-page":"2982","article-title":"Interleukin-31: the \u201citchy\u201d cytokine in inflammation and therapy","volume":"76","author":"Datsi","year":"2021","unstructured":"Datsi A, Steinhoff M, Ahmad F,  Interleukin-31: the \u201citchy\u201d cytokine in inflammation and therapy. Allergy 2021;76(10):2982\u201397."},{"issue":"6","key":"i1547-3317-62-3-127-b3","series-title":"Clin Pharmacol Drug Dev","first-page":"548","article-title":"The effect of verapamil, a P-glycoprotein inhibitor, on the pharmacokinetics of Peficitinib, an orally administered, once-daily JAK inhibitor","volume":"6","author":"Zhu","year":"2017","unstructured":"Zhu T, Howieson C, Wojtkowski T,  The effect of verapamil, a P-glycoprotein inhibitor, on the pharmacokinetics of Peficitinib, an orally administered, once-daily JAK inhibitor. Clin Pharmacol Drug Dev 2017;6(6):548\u201355."},{"key":"i1547-3317-62-3-127-b4","series-title":"Pharmacol Res","first-page":"9","article-title":"P-glycoprotein (MDR1\/ABCB1) and breast cancer resistance protein (BCRP\/ABCG2) restrict brain accumulation of the JAK1\/2 inhibitor, CYT387","volume":"76","author":"Durmus","year":"2013","unstructured":"Durmus S, Xu N, Sparidans RW,  P-glycoprotein (MDR1\/ABCB1) and breast cancer resistance protein (BCRP\/ABCG2) restrict brain accumulation of the JAK1\/2 inhibitor, CYT387. Pharmacol Res 2013;76:9\u201316."},{"issue":"1","key":"i1547-3317-62-3-127-b5","series-title":"J Vet Pharmacol Ther","first-page":"1","article-title":"Canine and feline P-glycoprotein deficiency: what we know and where we need to go","volume":"46","author":"Mealey","year":"2023","unstructured":"Mealey KL, Owens JG, Freeman E. Canine and feline P-glycoprotein deficiency: what we know and where we need to go. J Vet Pharmacol Ther 2023;46(1):1\u201316."},{"issue":"6","key":"i1547-3317-62-3-127-b6","series-title":"Drug Metab Dispos","first-page":"1073","article-title":"P-glycoprotein contributes to the blood-brain, but not blood-cerebrospinal fluid, barrier in a spontaneous canine p-glycoprotein knockout model","volume":"36","author":"Mealey","year":"2008","unstructured":"Mealey KL, Greene S, Bagley R,  P-glycoprotein contributes to the blood-brain, but not blood-cerebrospinal fluid, barrier in a spontaneous canine p-glycoprotein knockout model. Drug Metab Dispos 2008;36(6):1073\u201379."},{"issue":"4","key":"i1547-3317-62-3-127-b7","series-title":"J Vet Intern Med","first-page":"996","article-title":"ABCB1-1Delta polymorphism can predict hematologic toxicity in dogs treated with vincristine","volume":"22","author":"Mealey","year":"2008","unstructured":"Mealey KL, Fidel J, Gay JM,  ABCB1-1Delta polymorphism can predict hematologic toxicity in dogs treated with vincristine. J Vet Intern Med 2008;22(4):996\u20131000."},{"issue":"3","key":"i1547-3317-62-3-127-b8","series-title":"J Am Anim Hosp Assoc","first-page":"190","article-title":"Excessive cyclosporine-associated immunosuppression in a dog heterozygous for the MDR1 (ABCB1-1\u0394) mutation","volume":"56","author":"Mackin","year":"2020","unstructured":"Mackin AJ, Riggs C, Beatty T,  Excessive cyclosporine-associated immunosuppression in a dog heterozygous for the MDR1 (ABCB1-1\u0394) mutation. J Am Anim Hosp Assoc 2020;56(3):190."},{"issue":"11","key":"i1547-3317-62-3-127-b9","series-title":"J Am Vet Med Assoc","first-page":"1414","article-title":"Avermectin-induced neurotoxicity and mortality reported more commonly in cats homozygous for ABCB11930_1931del TC after application of eprinomectin-versus selamectin-containing products","volume":"263","author":"Mealey","year":"2025","unstructured":"Mealey KL, Burke NS, Huesser J,  Avermectin-induced neurotoxicity and mortality reported more commonly in cats homozygous for ABCB11930_1931del TC after application of eprinomectin-versus selamectin-containing products. J Am Vet Med Assoc 2025;263(11):1414\u201319."},{"issue":"8","key":"i1547-3317-62-3-127-b10","series-title":"JAMA Dermatol","first-page":"863","article-title":"Efficacy and safety of Abrocitinib in patients with moderate-to-severe atopic dermatitis: a randomized clinical trial","volume":"156","author":"Silverberg","year":"2020","unstructured":"Silverberg JI, Simpson EL, Thyssen JP,  Efficacy and safety of Abrocitinib in patients with moderate-to-severe atopic dermatitis: a randomized clinical trial. JAMA Dermatol 2020;156(8):863\u201373."},{"key":"i1547-3317-62-3-127-b11","series-title":"J Vet Pharmacol Ther.","article-title":"Comparison of human and canine P-glycoprotein substrates at R, P, and H binding sites","author":"Burke","year":"2025","unstructured":"Burke NS, Mealey KL. Comparison of human and canine P-glycoprotein substrates at R, P, and H binding sites [published online ahead of print November 19, 2025]. J Vet Pharmacol Ther. doi:10.1111\/jvp.70034."},{"issue":"3","key":"i1547-3317-62-3-127-b12","series-title":"Eur Geriatr Med","first-page":"463","article-title":"Adverse drug reactions in older adults: a narrative review of the literature","volume":"12","author":"Zazzara","year":"2021","unstructured":"Zazzara MB, Palmer K, Vetrano DL,  Adverse drug reactions in older adults: a narrative review of the literature. Eur Geriatr Med 2021;12(3):463\u201373."},{"issue":"3","key":"i1547-3317-62-3-127-b13","series-title":"J Am Vet Med Assoc","first-page":"472","article-title":"Drug-associated aplastic anemia in dogs: eight cases (1984\u20131988)","volume":"196","author":"Weiss","year":"1990","unstructured":"Weiss DJ, Klausner JS. Drug-associated aplastic anemia in dogs: eight cases (1984\u20131988). J Am Vet Med Assoc 1990;196(3):472\u20135."},{"issue":"9","key":"i1547-3317-62-3-127-b14","series-title":"J Am Vet Med Assoc","first-page":"1119","article-title":"Aplastic anemia associated with trimethoprim-sulfadiazine and fenbendazole administration in a dog","volume":"191","author":"Weiss","year":"1987","unstructured":"Weiss DJ, Adams LG. Aplastic anemia associated with trimethoprim-sulfadiazine and fenbendazole administration in a dog. J Am Vet Med Assoc 1987;191(9):1119\u201320."},{"issue":"6","key":"i1547-3317-62-3-127-b15","series-title":"Can Vet J","first-page":"269","article-title":"Reversible phenylbutazone-induced pancytopenia in a dog","volume":"25","author":"Badame","year":"1984","unstructured":"Badame FG, Van Slyke W, Hayes MA. Reversible phenylbutazone-induced pancytopenia in a dog. Can Vet J 1984;25(6):269\u201370."},{"issue":"1","key":"i1547-3317-62-3-127-b16","series-title":"Vet Clin Pathol","first-page":"122","article-title":"Bone marrow, blood, and clinical findings in dogs treated with phenobarbital","volume":"50","author":"Scott","year":"2021","unstructured":"Scott TN, Bailin HG, Jutkowitz LA,  Bone marrow, blood, and clinical findings in dogs treated with phenobarbital. Vet Clin Pathol 2021;50(1):122\u201331."},{"issue":"4","key":"i1547-3317-62-3-127-b17","series-title":"Vet Clin Pathol","first-page":"413","article-title":"A retrospective study of aplastic pancytopenia in the dog: 9 cases (1996\u20132003)","volume":"35","author":"Brazzell","year":"2006","unstructured":"Brazzell JL, Weiss DJ. A retrospective study of aplastic pancytopenia in the dog: 9 cases (1996\u20132003). Vet Clin Pathol 2006;35(4):413\u20137."},{"issue":"5","key":"i1547-3317-62-3-127-b18","series-title":"J Vet Pharmacol Ther","first-page":"417","article-title":"Biliary excretion of technetium-99m-sestamibi in wild-type dogs and in dogs with intrinsic (ABCB1-1Delta mutation) and extrinsic (ketoconazole treated) P-glycoprotein deficiency","volume":"32","author":"Coelho","year":"2009","unstructured":"Coelho JC, Tucker R, Mattoon J,  Biliary excretion of technetium-99m-sestamibi in wild-type dogs and in dogs with intrinsic (ABCB1-1Delta mutation) and extrinsic (ketoconazole treated) P-glycoprotein deficiency. J Vet Pharmacol Ther 2009;32(5):417\u201321."},{"issue":"1","key":"i1547-3317-62-3-127-b19","series-title":"Cell","first-page":"85","article-title":"Expression and activity of P-glycoprotein, a multidrug efflux pump, in human hematopoietic stem cells","volume":"66","author":"Chaudhary","year":"1991","unstructured":"Chaudhary PM, Roninson IB. Expression and activity of P-glycoprotein, a multidrug efflux pump, in human hematopoietic stem cells. Cell 1991;66(1):85\u201394."}],"container-title":["Journal of the American Animal Hospital Association"],"original-title":[],"link":[{"URL":"https:\/\/jaaha.kglmeridian.com\/view\/journals\/aaha\/62\/3\/article-p127.xml","content-type":"text\/html","content-version":"vor","intended-application":"text-mining"},{"URL":"https:\/\/jaaha.kglmeridian.com\/downloadpdf\/journals\/aaha\/62\/3\/article-p127.xml","content-type":"text\/html","content-version":"vor","intended-application":"syndication"},{"URL":"https:\/\/jaaha.kglmeridian.com\/downloadpdf\/journals\/aaha\/62\/3\/article-p127.xml","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2026,7,11]],"date-time":"2026-07-11T00:31:14Z","timestamp":1783729874000},"score":1,"resource":{"primary":{"URL":"https:\/\/jaaha.kglmeridian.com\/view\/journals\/aaha\/62\/3\/article-p127.xml"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2026,5,1]]},"references-count":19,"journal-issue":{"issue":"3"},"URL":"https:\/\/doi.org\/10.5326\/jaaha-ms-7552","relation":{},"ISSN":["1547-3317","0587-2871"],"issn-type":[{"value":"1547-3317","type":"electronic"},{"value":"0587-2871","type":"print"}],"subject":[],"published":{"date-parts":[[2026,5,1]]}}}