An open-label pilot study of oral vitamin C as an opioid-sparing agent in patients with chronic pain secondary to cancer.

ABSTRACT

PURPOSE: The purpose of this study is to assess the efficacy of oral Vitamin C as an opioid-sparing agent when used in conjunction with opioids and standard adjuvant therapy in the management of chronic cancer pain. METHODS: An open-label pilot study of patients ≥18 years of age with chronic pain secondary to cancer and/or its treatment and a Brief Pain Inventory average pain score of ≥3/10. In addition to opioid analgesia, patients received 1 g of vitamin C twice daily over 3 days (total daily dose of 2 g). Patients' usual medications, including breakthrough medications, were continued throughout the study period. The primary endpoint was total daily opioid use during vitamin C administration compared with that immediately prior to study. RESULTS: Thirty-four patients were enrolled in the study. Seven failed to complete the trial. Across the 17 evaluable patients, the median daily opioid consumption was 360 mg oral morphine equivalents (OME) on the days prior to vitamin C and 390 mg when administered with vitamin C. CONCLUSION: This study failed to demonstrate any clinically significant benefit from vitamin C in conjunction with opioids in cancer-related pain and does not provide support for embarking on a larger randomised trial to determine efficacy.