Retrospective evaluation of outpatient intravenous ketamine-lidocaine infusions for the palliation of cancer pain in dogs and cats

OBJECTIVE To evaluate the clinical benefit and adverse events following outpatient intravenous (IV) ketamine-lidocaine (KL) infusions for palliation of cancer pain in dogs and cats. METHODS Medical records from 15 years (2008 to 2023) were searched and data reviewed retrospectively. Animals were prescribed ketamine (0.15 mg/kg/h) and lidocaine (3 mg/kg/h in dogs and 1.5 mg/kg/h in cats) diluted in 250 mL (cats or dogs < 15 kg) or 500 mL (dogs >= 15 kg) of 0.9% saline administered IV at 2.5 mL/kg/h for 4 to 6 hours. RESULTS A total of 105 dogs and 9 cats (114 animals) were included. The most common tumor types treated were appendicular osteosarcoma in dogs (n = 45 [43%]) and oral squamous cell carcinoma in cats (4 [44%]). All animals received concomitant oral analgesic medications. Animals received a median of 2 KL infusions (range, 2 to 49 KL infusions). The overall clinical benefit rate was 76% following the first KL infusion, as defined by an improvement in at least 1 evaluated clinical sign. The likelihood of clinical response was improved with a ketamine infusion rate >= 2 <mu>g/kg/min, total ketamine dose of >= 0.5 mg/kg, and lidocaine infusion rate >= 25 mu g/kg/min. CONCLUSIONS Outpatient IV KL infusions were well-tolerated in dogs and cats with cancer and provided a high rate of clinical benefit when combined with standard anti-cancer and analgesic therapies. CLINICAL RELEVANCE Management of cancer pain often requires multimodal analgesia. Given the clinical benefit and minimal toxicity observed with outpatient KL infusions, KL infusions should be considered as an adjunctive treatment to use in combination with anticancer therapy, oral and topical analgesics, and interventional therapies in dogs and cats for palliation of refractory cancer pain from advanced disease.