Intravenous Lidocaine Response as a Predictor for Oral Oxcarbazepine Efficacy in Neuropathic Pain Syndrome: A Prospective Cohort Study

Abstract

BACKGROUND Providing pain relief for patients with neuropathic pain syndrome (NPS) is difficult, as sodium-channel blockers pose serious adverse events (AEs). Intravenous (i.v.) lidocaine infusion responses may identify patients likely to benefit from oral sodium channel blockers. We evaluated i.v. lidocaine responses to predict oral oxcarbazepine (OXC) efficacy in patients with NPS. MATERIAL AND METHODS This prospective cohort study administered one-time 3 mg/kg i.v. lidocaine infusion to patients with NPS. Numeric rating scale (NRS) pain scores and AEs were observed. Next, OXC 150 mg was prescribed; dosages were increased by 150 mg every 3 days until ≥50% pain reduction or the maximum tolerable dose or 1800 mg/day was reached. NRS, rescue drug requirements, and AEs were evaluated by phone at 1, 3, and 5 weeks and clinic visits at 2, 4, and 6 weeks. Depression, Anxiety &amp; Stress Scales 21 (DASS-21), and EuroQol-Five Dimensions-Five Levels (EQ-5D-5L) questionnaires were assessed at baseline and in week 6. RESULTS Of 46 patients, 14 discontinued due to intolerable AEs, and 32 were in the final analysis. Average post-intervention NRS significantly decreased from 6.8±1.7 (baseline) to 3.8±2.0 (lidocaine) and 4.1±2.3 (OXC); P<0.001. Negative and positive predictive values for OXC efficacy were 76.2% (95% CI: 61.6-86.5%) and 54.5% (95% CI: 32-75.4%), respectively. Six weeks after OXC treatment, 20 and 11 patients achieved ≥30% pain reduction and ≥50% pain relief, respectively. EQ-5D-5L (P=0.018) and DASS-21 stress dimension (P<0.001) significantly improved. CONCLUSIONS Negative responses to i.v. lidocaine predicted a lack of oral OXC response. AEs of OXC may have obscured an analgesic effect.