Effect of minocycline on lumbar radicular neuropathic pain: a randomized, placebo-controlled, double-blind clinical trial with amitriptyline as a comparator.
BACKGROUND
Less than 50% of patients experience sufficient pain relief with current drug therapy for neuropathic pain. Minocycline shows promising results in rodent models of neuropathic pain but was not studied in humans with regard to the treatment of neuropathic pain.


METHODS
In this randomized, double-blind, placebo-controlled clinical trial, patients with subacute lumbar radicular pain received placebo, amitriptyline 25 mg, or minocycline 100 mg once a day (n = 20 per group) for 14 days. Primary outcome measure was the pain intensity in the leg as measured by a numeric rating scale ranging from 0 to 10 on days 7 and 14. Secondary outcome measures were the reduction of neuropathic pain symptoms in the leg as determined with a neuropathic pain questionnaire, consumption of rescue medication, and adverse events on days 7 and 14.


RESULTS
Sixty patients were randomized and included in an intention-to-treat analysis. After 14 days, patients in the minocycline and amitriptyline groups reported a reduction of 1.47 (95% confidence interval, 0.16-2.83; P = 0.035) and 1.41 (95% confidence interval, 0.05-2.78; P = 0.043), respectively, in the numeric rating scale compared to the placebo group. No differences were seen in the neuropathic pain questionnaire values at any time point during treatment between the three groups. The rate of adverse events in the amitriptyline group was 10% versus none in the minocycline and placebo groups. No differences were noted in the consumption of rescue medication.


CONCLUSIONS
Although both groups differed from placebo, their effect size was small and therefore not likely to be clinically meaningful.
From the Department of Anesthesiology, Intensive Care Medicine and Multidisciplinary Pain Centre, Ziekenhuis Oost-Limburg, Genk, Belgium (P.V., J.V.Z., M.P., P.D.V., R.M., R.H.); Department of Anesthesiology, Pain and Palliative Medicine, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands (P.V., K.V.); Faculty of Medicine and Life Sciences, Hasselt University, Diepenbeek, Belgium (P.V.); and Department of Anatomy, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands (T.K., E.R.).
Pascal
P
Vanelderen
Jan
J
Van Zundert
Tamás
T
Kozicz
Martine
M
Puylaert
Pieter
P
De Vooght
Roel
R
Mestrum
René
R
Heylen
Eric
E
Roubos
Kris
K
Vissers
D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000639:Amitriptyline / Q000009:adverse effects / Q000627:therapeutic use; D018712:Analgesics, Non-Narcotic / Q000009:adverse effects / Q000627:therapeutic use*; D001416:Back Pain / Q000188:drug therapy*; D019208:Brain-Derived Neurotrophic Factor / Q000097:blood; D004311:Double-Blind Method; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D008911:Minocycline / Q000009:adverse effects / Q000627:therapeutic use*; D009437:Neuralgia / Q000188:drug therapy*; D010147:Pain Measurement / Q000187:drug effects; D013126:Spinal Nerve Roots / Q000473:pathology; D016896:Treatment Outcome; D055815:Young Adult
D018712:Analgesics, Non-Narcotic; D019208:Brain-Derived Neurotrophic Factor; D000639:Amitriptyline; D008911:Minocycline