The immediate effects of lidocaine iontophoresis on trigger-point pain

Objective: To assess the efficacy of lidocaine iontophoresis on myofascial trigger-point pain. Setting: University athletic training facility. Design: Randomized, double-blind, placebo-controlled, repeated-measures. Subjects: Twenty-three subjects with sensitive trigger points over the trapezius. Intervention: Placebo iontophoresis treatment without current or lidocaine, control treatment using distilled water and normal current dose, medicated treatment using 1 % lidocaine and normal current dose. Main Outcome Measure: Trigger-point pressure threshold assessed with an algometer. Results. ANOVA revealed a significant difference among treatments (F (2,40) = 7.38, P < .01). Post hoc comparisons revealed a significant difference in pressure threshold between the lidocaine treatment and the control (P =.01) and placebo (P =.001) treatments. Effect sizes of .28 and .39, respectively, were found for these comparisons. Conclusions: Although the data revealed significant differences between treatments, the small effect sizes and magnitude of the pressure-sensitivity deviation scores suggest that iontophoresis with 1 % lidocaine is ineffective in treating trigger points.