Recovery from Cyclophosphamide Overdose in a Dog

Area of Science:

• Veterinary Medicine
• Toxicology
• Pharmacology

Background:

• Cyclophosphamide is a widely used chemotherapy agent in veterinary oncology.
• Overdoses can lead to severe toxicity, including myelosuppression and hemorrhagic cystitis.
• Documenting outcomes of high-dose exposures is crucial for understanding toxicity thresholds.

Purpose of the Study:

• To report a case of a dog surviving an inadvertent, high-dose cyclophosphamide exposure.
• To detail the clinical signs, diagnostic findings, and treatment administered.
• To highlight the successful management and recovery from severe cyclophosphamide toxicity.

Main Methods:

• A case report of an adult spayed female dog inadvertently administered oral cyclophosphamide.
• Clinical evaluation including physical examination and hematology.
• Supportive care including antibiotics, blood transfusions, granulocyte colony stimulating factor, and tranexamic acid.
• Subsequent management of thrombocytopenia with vincristine, prednisolone, and melatonin.

Main Results:

• The dog received 1,750 mg of cyclophosphamide (2,303 mg/m²), a dose significantly higher than typically administered.
• Clinical signs included severe hemorrhagic cystitis and pancytopenia.
• Hematological recovery was achieved with supportive care, with neutrophil counts normalizing by day 14 and complete blood count near normal by day 21.
• A second episode of thrombocytopenia at day 51 was successfully managed.

Conclusions:

• Complete recovery was achieved in a dog following an inadvertent overdose of cyclophosphamide.
• This case represents the highest reported dose of cyclophosphamide associated with complete recovery in a canine patient.
• Aggressive supportive care and timely interventions are critical for managing severe chemotherapy-induced toxicities in dogs.