Transdermal cannabidiol has therapeutic potential for amelioration of experimental arthritis and secondary thermal hyperalgesia

Cannabinoids have been proven effective in relief of inflammatory pain, including arthritis pain. An increase in the duration of effect would significantly improve clinical efficacy. In the present study, knee joint monoarthritis was induced with complete Freund's adjuvant (CFA) in Sprague Dawley rats after baseline behavioral testing. Three days later secondary thermal hyperalgesia and knee joint inflammation were evident. The joint was swollen, and skin temperature was elevated. Secondary thermal hyperalgesia was assessed with both the Hargreave's paw withdrawal latency test and the hotplate test. A transdermal formulation of cannabidiol (CBD, 1%) was applied on four consecutive days to a 35 cm square area of skin on the rat's shaved back. Cannabidiol reduced secondary thermal hyperalgesia on each of the days upon testing four hours after cutaneous applications. Secondary thermal hyperalgesia was evident in untreated controls with monoarthritis. Subjective pain related posture score (0-5) improved from 4 in arthritic controls to 1 after cannabidiol treatment. Blood was drawn just prior to euthanasia and blood levels of cannabidiol determined. These studies indicate that transdermal cannabidiol has therapeutic potential for effective treatment of arthritic symptomatology.

(Supported by NIH RO1 NS 39041, ACS RSG-00-027-04-CDD and NIDA Drug Supply)