This research was designed as a pilot proof-of-concept study to evaluate the use of low-dose
methadone in post-herpetic
neuralgia patients who remained refractory after first and second line post-herpetic
neuralgia treatments and had indications for adding an
opioid agent to their current
drug regimens.
METHODS: This cross-over study was double blind and placebo controlled. Ten
opioid naïve post-herpetic
neuralgia patients received either
methadone (5 mg bid) or placebo for three weeks, followed by a 15-day washout period and a second three-week treatment with either
methadone or placebo, accordingly. Clinical evaluations were performed four times (before and after each three-week treatment period). The evaluations included the visual analogue scale, verbal category scale, daily activities scale, McGill
pain questionnaire, adverse events profile, and evoked
pain assessment. All patients provided written informed consent before being included in the study. ClinicalTrials.gov: NCT01752699 RESULTS:
Methadone, when compared to placebo, did not significantly affect the intensity of spontaneous
pain, as measured by the visual analogue scale. The intensity of spontaneous
pain was significantly decreased after the
methadone treatment compared to placebo on the category verbal scale (50% improved after the
methadone treatment, none after the placebo, p=0.031). Evoked
pain was reduced under
methadone compared to placebo (50% improved after the
methadone treatment, none after the placebo, p=0.031).
Allodynia reduction correlated with sleep improvement (r=0.67, p=0.030) during the
methadone treatment. The side effects profile was similar between both treatments.
CONCLUSIONS: