No beneficial effect of intrathecal methylprednisolone acetate in postherpetic neuralgia patients

Background High efficacy of intrathecal methylprednisolone acetate (MPA) with lidocaine has been reported in a large patient group suffering from intractable postherpetic neuralgia (PHN). Because the treatment effect was never independently confirmed and there are ongoing safety concerns, intrathecal MPA did not become standard care for intractable PHN. We report the results of a replication trial assessing pain relief and spinal cytokine/chemokine levels in PHN patients. Methods The number of patients to be included was determined using sequential analysis to limit patient exposure to the invasive experimental treatment. Patients were randomized to the treatment group receiving MPA 60mg+lidocaine 60mg or control group receiving lidocaine 60mg only. Four injections at 7-day intervals were administered after cerebrospinal fluid (CSF) collection to measure cytokine/chemokine levels. Visual analogue scores for pain and the square allodynic area were collected during follow-up, with the primary end point set at 8 weeks follow-up. Results In total, 10 patients were included, of whom six were randomized to the treatment group. All six MPA-treated patients experienced a pain increase at 8 weeks, versus one of four patients in the control group. The square allodynic area increased in four of six MPA-treated patients versus one of four control patients. CSF interleukin-8 levels remained stable in the control group, but increased significantly after the first intrathecal MPA injection. The trial was stopped because of safety concerns and futility. Conclusion Considering the absence of clinical benefits and the potential risks of the treatment, intrathecal administration of MPA is not recommended.