Prediction of Individual Analgesic Response to Intravenous Lidocaine in Painful Diabetic Peripheral Neuropathy: A Randomized, Placebo-controlled, Cross-over Trial.

Objectives Intravenous lidocaine can alleviate painful diabetic peripheral neuropathy (DPN) in some patients. Whether quantitative sensory testing (QST) can identify treatment responders have not been prospectively tested. Methods This was a prospective, randomized, double-blind, crossover, placebo-controlled trial comparing intravenous lidocaine to normal saline (placebo) for painful DPN. Thirty-four participants with painful DPN were enrolled and given intravenous lidocaine (5▒mg/kg ideal body weight) or placebo as a 40-minute infusion, after a battery of QST parameters were tested on the dorsal foot, with a three-week washout period between infusions. Results Thirty-one participants completed both study sessions and were included in the final analysis. Lidocaine resulted in a 51% pain reduction 60-120 minutes after infusion initiation, as assessed on a 0-10 numerical rating scale, while placebo resulted in a 33.5% pain reduction (difference=17.6%, 95% CI 1.9-33.3%, P=0.03). Neither mechanical pain threshold, heat pain threshold, nor any of the other measured QST parameters predicted the response to treatment. Lidocaine administration reduced mean Neuropathic Pain Symptom Inventory paresthesia/dysesthesia scores when compared to placebo by 1.29 points (95% CI -2.03 to -0.55, P=0.001), and paroxysmal pain scores by 0.84 points (95% CI -1.62 to -0.56, P=0.04), without significant changes in burning, pressing or evoked pain sub-scores. Discussion While some participants reported therapeutic benefit from lidocaine administration, QST measures alone were not predictive of response to treatment. Further studies, powered to test more complex phenotypic interactions, may be required to identify reliable predictors of response to pharmacotherapy in patients with DPN.