Low-Dose Diclofenac Approved for Management of Osteoarthritis Pain
Low-dose submicron diclofenac (Zorvolex) was approved by the U.S. Food and Drug Administration (FDA) for the management of osteoarthritis pain. The oral agent is the first FDA-approved low-dose nonsteroidal anti-inflammatory drug (NSAID).
The capsules contain diclofenac as submicron particles that are approximately 20 times smaller than their original size. The small particle size and increased surface area are said to lead to faster dissolution of the agent, according to the product manufacturer Iroko Pharmaceuticals.
The agent was designed to align with recommendations from the FDA and several professional medical organizations that NSAIDs be used at the lowest effective dose for the shortest possible duration, according to Iroko Pharmaceuticals.
Phase 3 Efficacy and Safety Data
Approval was based on a phase 3, 12-week study by Gibofsky et al of 305 patients (aged 41 to 90 years) with osteoarthritis of the hip or knee. Participants were randomized to diclofenac 35 mg three times daily (tid) or 35 mg twice daily (bid), or placebo. The patients were all chronic users of NSAIDs and/or acetaminophen and were having an osteoarthritis flare at baseline.
At 12 weeks, the 35-mg diclofenac tid group showed significant improvement over the placebo group in Western Ontario and McMasters Universities Osteoarthritis Index (WOMAC) pain subscale scores (-44.1 vs. -32.5; P=0.0024). In addition, both diclofenac groups showed greater improvement in average total WOMAC score compared with placebo (-35.9 with 35 mg tid and -30.3 with 35 mg bid vs. -23.2; P=0.0002 and P=0.0363, respectively).
Diarrhea, headache, nausea, and constipation were the most commonly reported treatment-related side effects.
The agent is also indicated for the management of mild to moderate acute pain in adults.