To assess the efficacy of glucosamine sulfate in knee osteoarthritis (OA).
A 4-center, 6-month, randomized, double-blind, placebo-controlled glucosamine discontinuation trial was conducted in 137 current users of glucosamine with knee OA who had experienced at least moderate improvement in knee pain after starting glucosamine. Study medication dosage was equivalent to the dosage of glucosamine taken prior to the study (maximum 1,500 mg/day). Followup continued for 6 months or until disease flare, whichever occurred first. The primary outcome was the proportion of disease flares in the glucosamine and placebo groups using an intent-to-treat analysis. Secondary outcomes included time to disease flare; analgesic medication use; severity of disease flare; and change in pain, stiffness, function and quality of life in the glucosamine and placebo groups.
Disease flare was seen in 28 (42%) of 66 placebo patients and 32 (45%) of 71 glucosamine patients (difference -3%; 95% confidence interval [95% CI] -19, 14; P = 0.76). In the Cox regression analysis, after adjustment for sex, study site, and OA radiographic severity, time to disease flare was not significantly different in the glucosamine compared with placebo group (hazard ratio of flare = 0.8; 95% CI 0.5, 1.4; P = 0.45). At final study visit, acetaminophen was used in 27% and 21% of placebo and glucosamine patients, respectively (P = 0.40), nonsteroidal antiinflammatory drugs were used in 29% and 30% (P = 0.92), and both were used in 20% and 21% (P = 0.84). No differences were found in severity of disease flare or other secondary outcomes between placebo and glucosamine patients.
In patients with knee OA with at least moderate subjective improvement with prior glucosamine use, this study provides no evidence of symptomatic benefit from continued use of glucosamine sulfate.