Phenobarbital Induced Pancytopenia in a 2.5 year old female spayed German Shepherd Dog

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A 2.5 year old spayed female German Shepherd Dog presented to the Cornell’s Emergency and Critical Care service for epistaxis and oral mucosal hemorrhage. The dog had a 5 day history of hemorrhage from the mouth, which progressed to bilateral epistaxis and bleeding from the vulva. The dog had been treated for 2 months with phenobarbital for presumptive idiopathic epilepsy, with a recent increase in dosage. An in-house hemogram performed at the primary care veterinarian revealed a moderate non-regenerative anemia, severe neutropenia, and severe thrombocytopenia. Given these findings, the dog was referred to the Cornell University Hospital for Animals.

On presentation, the dog was generally weak and lethargic but ambulatory. Vital parameters were within normal limits except for a rectal temperature of 103.8F (99.5-102.5F). There was bilateral epistaxis and moderate generalized hemorrhage from the gum lines in the oral cavity, but there was no active bleeding from the vulva. The dog bled from the skin during shaving for catheter placement but did not have petechiation or ecchymoses. Rectal examination revealed dark brown stool with no obvious melena or hematochezia. There was no free fluid in the thorax or abdomen on focused assessment with sonography for trauma. Point-of-care bloodwork revealed a mild metabolic acidosis with respiratory compensation and results within reference intervals for screening coagulation tests (prothrombin time and activated partial thromboplastin time). A moderate anemia of 28% (41-58%) and borderline hypoglycemia 62 mg/dL (63-118 mg/dL) were also noted. The problem list included pancytopenia, bleeding from mucosal surfaces; suspect sepsis; and a history of seizures with phenobarbital therapy. Differential diagnoses included a drug reaction, toxicosis, infection and cancer. A presumptive diagnosis of phenobarbital-induced pancytopenia with secondary sepsis was made.1, 2 Treatment was initiated with intravenous fluids with dextrose supplementation, ampicillin sulbactam, and enrofloxacin. Phenobarbital was discontinued and the dog was started on potassium bromide and levetiracetam for seizure control. An infusion of dimethyl sulfoxide platelets was given as part of a clinical trial. This presentation will highlight the diagnosis and supportive treatment for phenobarbital induced pancytopenia.

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Canine; adverse drug reaction; immune-mediated; bone marrow; Cytopenia


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