A single-center randomized controlled trial of local methylcobalamin injection for subacute herpetic neuralgia.

OBJECTIVE This study explored the efficacy of local methylcobalamin injection in relieving pain and improving the quality of life among subjects with subacute herpetic neuralgia. DESIGN A single-center, randomized controlled trial of local methylcobalamin injection was performed. SUBJECTS Ninety-eight subjects (age, ≥ 50 years) with unilateral, dermatomal pain ≥ 4 related to herpes zoster on the torso lasting for 30 days after onset of rash were enrolled. METHODS Subjects were randomized to receive local methylcobalamin injection (N = 33), oral methylcobalamin (N = 33), or subcutaneous 1.0% lidocaine injection (N = 32) for 4 weeks. Worst pain severity, global impression of change, continuous spontaneous pain, paroxysmal pain, allodynia, paresthesia, interference with activities of daily living, and quality of life were assessed after 28-day treatment period. RESULTS Time per group interaction and group difference on overall pain at each follow-up point were statistically significant (P < 0.001) among groups. In the injected methylcobalamin group, the overall pain (P < 0.001), continuous spontaneous pain (P < 0.05), paroxysmal pain (P < 0.05), and allodynia (P < 0.05) revealed a significant effect at each follow-up point as compared with the other groups. Twenty subjects achieved pain reduction ≥ 50%, 24 perceived worst pain ≤ 3, 24 stopped using analgesics at end point; activities of daily living and quality of life improved significantly as compared with the other groups (P < 0.001). Although both of the other groups showed a significant response after the 14-day treatment (P < 0.001) compared with the baseline, oral methylcobalamin did not provide any significantly pain relief (P > 0.05). CONCLUSIONS Local methylcobalamin injection was not only efficacious in relieving pain, but also appears to be tolerable and a potential choice of treatment for subacute herpetic neuralgia.