C. Hammell, L. P. Zhang, F. M, S. M. Abshire, S. L. McIlwrath, A. L. Stinchcomb, K. N. Westlund
- Topical CBD proved to be an effective symptomatic, anti-inflammatory and anti-hyperalgesic treatment in arthritis
- A dose of 6.2mg/day of CBD significantly reduced swelling and synovial thickness
- Transdermal CBD use improved pain, reducing the median score from 4 to 1.5 (0-5 scale)
- Only after 2 days of CBD treatment, there was a significant improvement of heat hypersensitivity, which persisted throughout the experiment
- Pro-inflammatory activity dropped as low as non-pathological levels after using CBD
- The subjects didn’t suffer any alteration in their activity levels or motor abilities.
OBJECTIVES & HYPOTHESIS → The aim of this study was to study the in vivo efficacy of transdermal CBD to reduce inflammation and pain-related behaviors. Moreover, potential adverse effects were also assessed, in an attempt to provide a safe and effective alternative for the current arthritis treatments which often have side-effects.
METHODS → 54 rats were used in the experiments, of which 21 were used as control and 23 were subjected to adjuvant-induced monoarthritis. On day 3 after the onset of arthritis, vehicle gel or CBD gel was applied by rubbing it into the skin for 30s. The doses of CBD used per day were: 0.62 mg, 3.1mg, 6.2mg, 62mg. The criteria assessed was the following: joint circumference; spontaneous pain using a scale from 0-5; hindpaw heat sensitivity; and animal behavior. The levels of immunomodulator molecules and immunoreactivity were also determined.
RESULTS → 3 days after the onset of induced-monoarthritis, a series of pathological changes were noted: increased swelling alongside a knee joint circumference increase; thickening of the synovial membrane; high pain levels (median score of 4); and decrease of the average paw withdrawal latency (PWL), which measures hypersensitivity. After only 4 days of daily applications of transdermal CBD, all these pathological situations were reversed. 6.2 mg/day of CBD use reduced the knee joint circumference by 10.0% and dosages of 62.3 mg/day reduced it by 14.2%, while membrane thickness was decreased by more than 50%. The pain scores improved to a median of 1.5 compared to animals in the vehicle control group, which suffered no change. A significant improvement of heat hypersensitivity was also noted with the higher doses of CBD, whereas PWL values were not changed by application of vehicle. Moreover, immunoreactivity decreased, having been demonstrated a reduction of the levels of OX42 and TNFα immunoreactivity to, or even below, non-pathological levels. Lower doses of CBD (0.6mg and 3.1mg/day) had no effect on CFA-induced edema, synovial membrane thickness, pain scores nor PWL.
No changes were detected for total time spent in either exploratory activity or resting, indicating that CBD did not alter the animals’ activity levels or motor abilities.