Peer-reviewed veterinary case report
Pancytopenia caused by ilunocitinib in Australian Shepherd with MDR1
By Mealey, Katrina L et al.·Published in Journal of the American Animal Hospital Association·2026·View original on PubMed →
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Original publication title: Ilunocitinib-Induced Pancytopenia in an Australian Shepherd Dog with the MDR1 Mutation.
- Species:
- dog
Plain-English summary
A 5-year-old female spayed Australian Shepherd with a history of skin allergies was brought in for worsening itching, despite receiving immunotherapy. The vet prescribed a medication called ilunocitinib to help with the itching, but after one month, blood tests showed a serious drop in red blood cells, white blood cells, and platelets, a condition known as pancytopenia. The medication was stopped, and after a week, the dog's blood cell counts began to improve, and by one month later, all blood counts returned to normal. This case highlights that ilunocitinib should be used carefully in dogs with a specific genetic mutation that affects drug metabolism.
People also search for: Australian Shepherd itching treatment · ilunocitinib side effects in dogs · dog blood test results explained
Abstract
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's 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-mediated 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.
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Search related cases →Original publication on PubMed: https://pubmed.ncbi.nlm.nih.gov/42014054/