Minocycline Does Not Decrease Intensity of Neuropathic Pain Intensity, But Does Improve Its Affective Dimension

Recent understanding of the neuron-glia communication shed light on an important role of microglia to develop neuropathic pain The analgesic effect ofminocycline on neuropathic pain is promising but it remains unclear in clinical settings. This study included 20 patients with neuropathic pain of varied etiologies. We administered 100 mg/day of minocycline for 1 week and then 200 mg/day for 3 weeks, as an open-label adjunct to conventional analgesics. An 11-point numerical rating scale. (NRS) and the short-form McGill Pain Questionnaire (SF-MPQ) were used to evaluate pain severity. The data were collected at baseline and after 4 weeks of therapy and analyzed using the Wilcoxon signed-rank test. All except two of the patients tolerated the full dose of minocycline. There was no significant improvement in the scoring of NRS (5.6 +/- 1.2 at baseline vs. 5.3 +/- 1.9 at 4 weeks; P = .60). The total score of the SF-MPQ decreased significantly (17.2 +/- 7.4 vs. 13.9 +/- 9.6; P = .02), particularly in the affective subscale (4.4 +/- 2.7 vs. 3.3 +/- 3.6; P = .007) but not so in the sensory subscale (12.8 +/- 5.2 vs. 10.6 +/- 6.2; P = .06). We conclude that minocycline failed to decrease pain intensity but succeeded in reducing the affective dimension associated with neuropathic pain.