Pharmacokinetics of bleomycin in dogs treated with electrochemotherapy

Bleomycin (BLM) is a cytotoxic antibiotic used in veterinary oncology, primarily in electrochemotherapy (ECT), a local ablative therapy where electric pulses increase drug uptake in tumours. BLM is administered intravenously or intratumourally, with the standard intravenous dose for dogs being 15,000 IU/m², followed by electric pulses 8-10 minutes later. This protocol is derived from human oncology and lacks extensive pharmacological data in dogs. We studied BLM pharmacokinetics in 29 dogs with various tumours treated with intravenous BLM and ECT between 2017 and 2023. Samples were collected from serum of 15 dogs, serum and tumours of 8 dogs, and tumours of 6 dogs. The mean volume of distribution (Vd) of BLM was 224.5 ± 75.02 ml/kg, clearance (CL) was 7.04 ± 2.05 ml/kg/min, and area under the curve (AUC) was 65.87 ± 2.11 µg·min/l. The half-life (t₁_/₂) of BLM in dogs was 22.03 ± 0.88 minutes. No significant difference was found in tumour BLM concentrations between 8 minutes post-administration and 2 minutes after pulse completion. These results support the recommended 8-28-minute window for applying electric pulses following intravenous BLM administration and may indicate no need for dose adjustments based on body weight or age.