A deadly mix‐up: The incorrect dispensing of cyclophosphamide for cyclosporine resulting in a pancytopaenia and haemorrhagic cystitis

Abstract A 10‐year‐old, male, Staffordshire bull terrier was presented to a veterinary hospital for a suspected snake envenomation. Three weeks prior, the patient was diagnosed with discoid lupus erythematosus and was prescribed cyclosporine. A complete blood count and chemistry panel revealed severe thrombocytopaenia, severe leukopaenia and mild anaemia of unknown aetiology. Severe thrombocytopaenia and leukopaenia persisted for 13 days. The patient developed severe haematuria, despite receiving intravenous fluids, vitamin K1, B12 injections and Yunnan Baiyao. Over subsequent hospital visits, the patient became recumbent and anuric. Due to poor prognosis and lack of clinical response, the patient was euthanased and submitted for a postmortem examination. Postmortem examination suggested a myelotoxic insult leading to pancytopaenia and sterile haemorrhagic cystitis. Cyclophosphamide toxicity was considered, which is known to cause these two conditions. When presented with the findings, the owner realised that the retail pharmacy had erroneously dispensed cyclophosphamide instead of cyclosporine.