Ms. Wallace et al., Efficacy of oral mexiletine for neuropathic pain with allodynia: A double-blind, placebo-controlled, crossover study, REG ANES PA, 25(5), 2000, pp. 459-467
Background and Objectives: Mexiletine is an oral sodium channel antagonist
that has been reported to be effective in a variety of neuropathic pain syn
dromes. However, recent reports question the efficacy of oral mexiletine in
neuropathic pain. The objectives of this study were to examine the effect
of oral mexiletine on pain, neurosensation, allodynia, and quality of life.
Methods: Twenty subjects suffering from neuropathic pain with prominent all
odynia were enrolled in a randomized placebo-controlled crossover study. Pa
tients were titrated to a maximum dose of 900 mg/d or dose-limiting side ef
fects, whichever occurred first. At baseline and on days 0, 4, 7, and 10, t
he following tests were performed: (1) Quality of Life Questionnaires; (2)
pain scores; (3) area of allodynia; (4) side effects; (5) neurosensory test
ing; and (6) peak and trough plasma mexiletine levels.
Results: Peak plasma levels occurred on day 10 and were 0.54 mu g/mL. There
was no significant effect on any quality of life measurement. There was no
significant effect on any neurosensory threshold or the area of allodynia.
There was a significant effect of mexiletine on stroking-induced pain. The
re were no significant effects on any other pain score. Side effects were n
egligible.
Conclusions: At doses of up to 900 mg/d, mexiletine has minimal effects on
pain and allodynia of neuropathic pain. However, side effects may preclude
higher doses.