There are few efficacious treatments for mechanical neck pain, with controlled trials suggesting efficacy for muscle relaxants and topical non-steroidal anti-inflammatory drugs. Although studies evaluating topical lidocaine for back pain have been disappointing, the more superficial location of the cervical musculature suggests a possible role for topical local anesthetics.
We performed a randomized, double-blind, placebo-controlled crossover trial at 4 U.S. military, Veterans Administration, academic and private practice sites in which 76 patients were randomized to receive either placebo followed by lidocaine patch for 4-week intervals (group 1) or a lidocaine-placebo patch sequence. The primary outcome measure was mean reduction in average neck pain, with a positive categorical outcome designated as a ≥2-point reduction in average neck pain coupled with a ≥5/7 score on the Patient Global Impression of Change scale at the 4-week endpoint.
For the primary outcome, the median reduction in average neck pain score was -1.0 (IQR -2.0, 0.0) for the lidocaine phase vs. -0.5 (IQR -2.0,.0) for placebo treatment (p=0.17). 27.7% of patients experienced a positive outcome during lidocaine treatment vs. 14.9% during the placebo phase (p=0.073). There were no significant differences between treatments for secondary outcomes, though a carryover effect on pain pressure threshold was observed for the lidocaine phase (p=0.015). 27.5% of patients in the lidocaine group and 20.5% in the placebo group experienced minor reactions, the most common of which was pruritis (p=0.036).
The differences favoring lidocaine were small and non-significant, but the trend towards superiority of lidocaine suggests more aggressive phenotyping and applying formulations with greater penetrance may provide clinically meaningful benefit.