Safe and Effective Treatment of Refractory Cancer Pain with Chronic Oral Ketamine: A Case Series

Introduction: A growing body of evidence supports the off-label use of subanesthetic or low-dose oral ketamine for chronic pain. However, the safety and efficacy of long-term treatment remain unclear. This case series describes one palliative care (PC) clinic's experience using long-term oral ketamine to treat refractory cancer pain.Methods: All patients (n = 3) treated with oral ketamine in one PC clinic between 2022 and 2024 for adult cancer pain were reviewed. Pain scores were collected using the Edmonton Symptom Assessment Scale numeric rating scale as part of routine follow-up visits.Results: All patients reported improvement in cancer-related pain with the addition of oral ketamine. The total daily dose ranged from 30 mg to 320 mg. One patient experienced mild dissociative effects and dizziness, which resolved after decreasing the total daily dose. Treatment was maintained beyond 3 months in 2/3 cases, and the longest course of therapy was 18 months. The most significant logistical challenge was related to supply chain issues limiting availability at community pharmacies.Conclusion: Chronic treatment with oral ketamine as a coanalgesic for refractory cancer pain was well tolerated. All patients reported improved pain scores with the addition of oral ketamine. Ongoing research is needed to further describe the risks and benefits of long-term oral ketamine treatment.