Treating Patients with Knee Osteoarthritis with Topical Diclofenac Sodium 1% Gel

Las Vegas—A post-hoc analysis of 3 similar 12-week, randomized, double-blind, parallel-group, multicenter trials found that patients with knee osteoarthritis (OA) who used topical diclofenac sodium 1% gel had significant improvements in pain and physical function compared with patients who received placebo gel. The results, presented at the AAPM meeting during a poster presentation titled Topical Diclofenac Sodium Gel in Older and Younger Patients, were similar for patients <65 years of age and those ≥65 years of age. According to the authors, topical diclofenac sodium 1% gel reduced peak plasma diclofenac levels 150-fold and mean plasma levels 17-fold in a previous study compared with oral diclofenac. Topical diclofenac sodium 1% gel is among several nonsteroidal anti-inflammatory drugs (NSAIDs), which are typically used to treat knee OA but are often associated with gastrointestinal, cardiovascular, and renal adverse events. In this trial patients were included if they were ≥35 years of age; had symptomatic knee OA for ≥6 months; received daily treatment of target knee pain with oral NSAIDs, cyclooxygenase-2 inhibitors, or acetaminophen for ≥2 weeks during the month before screening; pain on movement score ≥50 on a 100-mm visual analog scale; and pain score ≥9 on the 0 to 20 scale Western Ontario and McMaster Universities Osteoarthritis (WOMAC) index. They were excluded if they had a history of or currently had secondary OA, rheumatoid arthritis, other chronic inflammatory joint diseases, or fibromyalgia; were allergic to study medications; or had used a topical analgesic or anti-inflammatory in the previous month. After an analgesic washout period ≥1 week, patients were randomized in a 1:1 ratio to receive topical diclofenac sodium 1% gel or vehicle medication. Each patient received 4 g of the study drug applied to their knees 4 times daily for 12 weeks. They could also receive 500 mg of acetaminophen as rescue medication to a maximum of 4 g daily. In their analysis, the authors divided the patients by age: <65 years or ≥65 years. At baseline, the demographics were similar for the groups. Of the 602 patients <65 years of age, the mean age was approximately 54 years, and the mean body mass index (BMI) was approximately 32 kg/m2. Approximately 62% of the patients were women, and the mean WOMAC index score was 12.3. Of the 374 patients ≥65 years of age, the mean age was approximately 72 years, and the mean BMI was approximately 30 kg/m2. Approximately 65% of the patients were women, and the mean WOMAC index score was approximately 12.0. In the group <65 years of age, the mean improvement in the WOMAC pain index, the physical function index, the global rating of disease, and the pain on movement score was significantly higher for patients who received topical diclofenac sodium 1% gel compared with those who received the vehicle medication (P=.007; P=.002; P=.01; and P<.001, respectively). Patients ≥65 years of age who used topical diclofenac sodium 1% gel also had a significantly greater improvement compared with those who used the vehicle medication, as measured by the WOMAC pain index (P=.02), the physical function index (P=.004), and the pain on movement score (P=.02). There was no statistically significant difference in the global rating of disease in patients ≥65 years of age who used topical diclofenac sodium 1% gel compared with those who used the vehicle medication. The adverse event rates were similar for the groups ≥65 years of age and <65 years of age. The most common adverse events were application site reactions; gastrointestinal adverse events were infrequent. This study was funded by Endo Pharmaceuticals, Inc.