Two Developments in Osteoarthritis Pain Treatment
Two developments this year provide some hope for more over-the-counter options for people with osteoarthritis pain: Diclofenac sodium gel is now available without a prescription. And turmeric extract was shown in a new study to provide moderate pain relief for knee osteoarthritis, although more research is needed with a larger sample size.
OTC Diclofenac Gel
In the spring of 2020, the FDA approved diclofenac sodium gel (Voltaren, GlaxoSmithKline) for over-the-counter sale as a topical nonsteroidal anti-inflammatory drug (NSAID) for the temporary relief of arthritis pain in the hand, wrist, elbow, foot, ankle, or knee in adults.
It is the first prescription-strength NSAID topical gel for arthritis pain to be available over the counter in the United States.
The amount of diclofenac sodium that is systemically absorbed from Voltaren Arthritis Pain is on average 6% of the systemic exposure from an oral form of diclofenac sodium.
Curcuma Longa Extract
As for turmeric (curcuma longa), a small study published in the Annals of Internal Medicine reported that curcuma longa extract (CL) was more effective than placebo for knee pain but did not affect knee effusion-synovitis or cartilage composition. The single-center study in Tasmania, Australia, was a randomized, double-blind, placebo-controlled trial, with 70 participants who suffered from symptomatic knee osteoarthritis and ultrasonography-defined effusion-synovitis.
The participants took 2 capsules per day of either CL (n = 36) or matched placebo (n = 34) for 12 weeks.
CL improved visual analog scale pain compared with placebo by -9.1 mm [95% confidence interval CI, -17.8 to -0.4 mm (P = 0.039)] but did not change effusion-synovitis volume [3.2 mL (CI, -0.3 to 6.8 mL)].
CL also improved Western Ontario and McMaster Universities Arthritis Index (WOMAC) knee pain [-47.2 mm (CI, -81.2 to -13.2 mm); P = 0.006] but not lateral femoral cartilage T2 relaxation time [-0.4 ms (CI, -1.1 to 0.3 ms)]. The incidence of adverse events was similar in the CL [n = 14 (39%)] and placebo [n = 18 (53%)] groups (P = 0.16); 2 events in the CL group and 5 in the placebo group may have been treatment related.
Multicenter trials with larger sample sizes are needed to assess the clinical significance of these findings, the authors report. However, the findings are significant because current pharmacologic treatments for patients with arthritis "are suboptimal," the authors write, and the resulting decrease in physical activity can lead to other more serious decline in health for patients. (See Wang Z, Jones G, Winzenberg, T. Effectiveness of curcuma longa extract for the treatment of symptoms and effusion-synovitis of knee osteoarthritis-a randomized trial [published online ahead of print September 15, 2020]. Ann of Intern Med. doi:10.7326/M20-0990.)