Penetration of Topical Glucosamine Sulfate into the Synovial Fluid of Patients with Knee Osteoarthritis: A Nonrandomized, Open-Label, Single Dose, Bioavailability Study

Objective: This study aims to show that a proprietary topical cream can deliver glucosamine through the skin into the synovial fluid of osteoarthritic patients. This cream contains 10% w/w glucosamine sulfate. It also aims to determine the endogenous level of glucosamine in the synovial fluid of these patients. Therapeutic effectiveness of glucosamine is not addressed in this study. Design: This phase IV, open-label, nonrandomized study enrolled 240 patients. Participants from the Test group received a single dose treatment (2 g of cream), and synovial fluid samples were collected 1 - 3 hours post-treatment. Patients from the Control group were not subjected to any treatment but their synovial fluid was also sampled to establish a glucosamine concentration baseline for Time-0 (T0). Glucosamine concentrations were determined by HPLC analysis. Results: The mean glucosamine concentration in the synovial fluid of patients from the Test group (100.56 ng/ml, 95% CI 66.36 - 134.76, n = 117) was higher than in the Control group (17.83 ng/ml, 95% CI 7.42 - 28.24, n = 117) resulting in a significant between-group difference (p < 0.0001). While the gender of the subjects did not appear to affect the results, a significant difference was observed with age variation. Conclusion: The results suggest that glucosamine can be topically delivered across the human skin into the synovial fluid using a proper vehicle. This suggests that other water-soluble molecules could similarly be delivered transdermally, alleviating the need for oral delivery in cases where oral administration is difficult, or when harmful side effects could ensue.