Intermetatarsal neuroma or
Morton's neuroma is a painful condition of the foot resulting from an entrapment of the common digital nerve typically in the third intermetatarsal space. The
pain can be severe and especially problematic with walking. Treatment options are limited and surgery may lead to permanent
numbness in the toes.
Capsaicin, the pungent ingredient of hot peppers, produces
analgesia by inducing retraction of nociceptive afferents from the area of innervation and is effective in treating certain
neuropathic pain disorders. A randomized double-blind placebo-controlled study was conducted to test the efficacy, tolerability, and safety of a single 0.1 mg dose of
capsaicin vs placebo injected into the region of the
neuroma. A total of 58 subjects diagnosed with
Morton's neuroma with foot
pain ≥4 (0-10 numerical
pain rating scale) were injected with 2 mL of
lidocaine into the intermetatarsal space proximal to the
neuroma to provide
local anesthesia. After 5 minutes, 0.1 mg
capsaicin or placebo was injected into the intermetatarsal space containing the painful
neuroma. Average foot
pain was rated for 2 weeks before through 4 weeks after injection. At weeks 1 and 4, the decrease in
pain was significantly greater in the subjects treated with
capsaicin (P = 0.021 and P = 0.019, respectively). A trend toward significance was noted at weeks 2 and 3. Improvements in functional interference scores and reductions in oral
analgesic use were also seen in the
capsaicin-treated group. These findings suggest that injection of
capsaicin is an efficacious treatment option for patients with painful
intermetatarsal neuroma.