Subcutaneous injection of botulinum toxin a is beneficial in postherpetic neuralgia.

Objective: To assess the benefits of subcutaneous injection of botulinum toxin A (BTX-A) for the treatment of postherpetic neuralgia (PHN).

Design: We investigated the therapeutic benefits of BTX-A in subjects with PHN in a randomized, double-blind, placebo-controlled study. Sixty subjects with PHN were randomly and evenly distributed into BTX-A, lidocaine, and placebo groups.

Measures: After randomization, one of the following solutions was injected subcutaneously in the affected dermatome: 5u/mL BTX-A, 0.5% lidocaine, or 0.9% saline (placebo). Visual analog scale (VAS) pain and sleeping time (hours) were evaluated at the time of pretreatment, day 1, day 7, and 3 months posttreatment. Opioid usage was calculated at day 7 and 3 months posttreatment.

Results:   Compared with pretreatment, VAS pain scores decreased at day 7 and 3 months posttreatment in all three groups (P<0.01). However, the VAS pain scores of the BTX-A group decreased more significantly compared with lidocaine and placebo groups at day 7 and 3 months posttreatment (P<0.01). Sleep time (hours) had improved at day 7 and at 3 months compared with pretreatment in all three groups, but the BTX-A group improved more significantly compared with lidocaine and placebo groups (P<0.01). The percent of subjects using opioids posttreatment in the BTX-A group was the lowest (21.1%) compared with the lidocaine (52.6%) and placebo (66.7%) groups (P<0.01).

Conclusions: Subcutaneous administration of BTX-A significantly decreased pain in PHN and reduced opioid use compared with lidocaine and placebo at day 7 and 3 months post-treatment. It also increased subjects' sleep times.