Peer-reviewed veterinary case report
Blood and bone marrow changes in dogs on phenobarbital treatment
By Scott, Tiffany N et al.·Published in Veterinary clinical pathology·2021·Department of Pathobiology and Diagnostic Investigation, United States·View original on PubMed →
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Original publication title: Bone marrow, blood, and clinical findings in dogs treated with phenobarbital.
- Species:
- dog
Plain-English summary
A 5-year-old mixed-breed dog was brought in for low energy and unusual bleeding after being treated with phenobarbital for seizures. Blood tests showed low levels of red and white blood cells, indicating a condition called cytopenia, which can occur with this medication. The veterinarian found that the dog's bone marrow was not producing enough healthy blood cells, but after adjusting the treatment, the dog's blood cell counts improved within about two weeks. The dog is now recovering well and has returned to normal activity levels.
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Abstract
BACKGROUND: Cytopenias have been reported in dogs treated with phenobarbital, but detailed descriptions of bone marrow findings and response to treatment are lacking. OBJECTIVES: We aimed to characterize the hematologic findings and clinical outcomes of dogs that had been receiving phenobarbital at the time of marrow evaluation. METHODS: Archived bone marrow slides and clinicopathologic data were reviewed in dogs undergoing marrow evaluation for any hematologic problems that developed while receiving phenobarbital (2008-2020). Dogs were excluded if marrow samples lacked diagnostic value, phenobarbital was withdrawn >1 day before marrow collection, a same-day complete blood count (CBC) was lacking, or dogs had concurrent illness or therapy known to cause cytopenias. RESULTS: Thirteen dogs met inclusion criteria: eight pancytopenic, three anemic/thrombocytopenic, one neutropenic/thrombocytopenic, and one nearly neutropenic. Neutropenia was marked (<700/µL) in eight dogs; all neutrophil concentrations were low or low-normal. Of the 11 anemic dogs (Hct = 12%-42%, median = 29%), three had mild reticulocytosis (eight were tested). One dog had erythroid dysplasia in blood and marrow. All nine neutropenic dogs had evidence of ineffective neutropoiesis: neutrophilic hyperplasia with left shift (9) ± neutrophagocytosis (5). Eight of the 11 anemic dogs had evidence of ineffective erythropoiesis: erythroid hyperplasia (7), left shift (3), and/or rubriphagocytosis (6). No thrombocytopenic dog had megakaryocytic hypoplasia; seven dogs had megakaryocytic hyperplasia. One anemic/thrombocytopenic dog had marked collagen myelofibrosis. The noncytopenic dog had equivocal myeloid hypoplasia with neutrophagocytosis. Median maximal responses and resolution times for neutropenia (n = 6) were 14 days. CONCLUSIONS: Phenobarbital-induced cytopenias should be considered in dogs with multilineage ineffective hematopoiesis, particularly when neutropenia and myeloid hyperplasia are present. However, findings in dogs with immune-mediated neutropenia or precursor-targeted immune-mediated anemia might be indistinguishable.
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Search related cases →Original publication on PubMed: https://pubmed.ncbi.nlm.nih.gov/33751634/