To compare the analgesic efficacy of two different doses of epidural ketamine in chronic low back-pain patients: A randomised double-blind study

Background and Aims: Ketamine, an adjunct to epidural steroid injections (ESI) for chronic back-pain provides better quality and prolonged duration of analgesia. The present study aims to evaluate the analgesic efficacy in terms of pain scores, duration of pain-free period, patient satisfaction score (PSS) and number of repeat injections with 25 mg versus 50 mg ketamine as adjuvants to ESI. Methods: In a prospective, randomised, double-blind trial at a tertiary care hospital, 60 patients of chronic low back-pain of either sex, aged 18–65 years, received preservative free 25 mg ketamine in Group I and 50 mg ketamine in Group II as adjunct to 40 mg triamcinolone in total 6 ml volume given epidurally. Baseline data along with follow-ups at 2, 4, 8 and 12 weeks post-procedure included assessment of pain using Visual Analogue Scale (VAS), duration, number of repeat blocks using PSS, Quality of Life (QoL) and side-effects. Categorical data analysed using the Chi-Square test, and continuous data using paired t-test. Results: Pain evaluation within the groups over time showed significant improvement from baseline (P = 0.000), and between the groups showed comparable VAS scores at 12 weeks (P = 0.392). The PSS, pain-free duration and number of repeat injections were also statistically comparable. However, the QoL improved more in Group II vs Group I (P = 0.024). The short-lasting side effects were more in Group II, but no features of neurotoxicity were observed in any patient. Conclusion: The analgesic efficacy of adjuvant therapy with 50 mg ketamine appeared comparable to 25 mg ketamine. Although, there was a better quality of life and longer pain-free interval with 50 mg ketamine, the side effects were more.