Objectives: 

Chronic pain, a devastating, widespread problem, is a syndrome that cuts across traditionally defined disciplinary boundaries within the health sciences. The present study explored the effects of a chili pepper extract (Capsaicin) on pain and inflammation in a rat model of adjuvant-induced arthritis (AIA).

Materials: 

Tibio-tarsian arthritis was induced in white Wistar rats by subcutaneous injections with Freund adjuvant (FA) in the left hind paw. Four groups were compared: a non-arthritis control group and three AIA groups treated orally with saline solution, non steroidal anti-inflammatory agents (Indomethacin) and Capsaicin. After 21 days the change in the paw volume (as an indicator of edema) was measured with a plethysmometer, and nociception was evaluated by applying mechanical pressure on the hind paw.

Results: 

A large increase was observed in the hind paw volume of untreated, saline-treated arthritic rats compared with non-arthritic rats. Our results showed that Indomethacin (2 mg/kg/day) and Capsaicin (2 mg/kg/day) treatments significantly decreased the edema and mechanical hyperalgia both in the FA treated paw and in the opposite one compared with non-arthritic or saline-treated arthritic rats. In contrast, arthritic rats treated with Capsaicin and Indomethacin showed a gradual but significant decrease in their paw volumes until the end of the experiment. Capsaicin effectively lowered the pain score of AIA rats from day 21 after the induction of arthritis, its efficiency being similar to that of Indomethacin.

Conclusions: 

The study confirms the analgesic effect and the anti-inflammatory efficiency of Capsaicin.