Background and aims We have previously reported that
sinomenine, an
alkaloid isolated from the root of the plant Sinomenium acutum, had antinociceptive effect in rodent models of acute inflammatory or
neuropathic pain. As a
traditional medicine,
sinomenine is used in China to treat
rheumatoid arthritis (RA). Methods In the present study, we evaluated the potential antinociceptive effect of
sinomenine in a mouse model of RA,
collagen type II antibody (CII Ab) induced
arthritis (CAIA) after acute and chronic administration. Results As single administration,
sinomenine at 40 or 80 mg/kg significantly reduced mechanical
hypersensitivity both at the time of peak joint
inflammation (days 11-19 after CII Ab injection) or during the post-inflammatory phase (days 35-54). No tolerance to the effect of 80 mg/kg
sinomenine was observed during repeated injection twice a day for 5 days from day 11 to day 19 or from day 49 to day 53 after CII Ab injection in CAIA mice. Conclusions We have shown that
sinomenine is effective in alleviating localized and spread
hypersensitivities in CAIA mice both during acute
inflammation and in post-inflammatory phase. Further, repeated
sinomenine administration has elevated the baseline mechanical threshold without producing tolerance. Implications
Sinomenine may be clinically useful to treat
chronic pain in RA, including wide-spread
pain which appears to be a difficult clinical problem despite the improvement in the acute treatment of RA by disease modifying agents.