The stereochemistry was not fully determined until the 1939 work of Walter Haworth. In the United States, glucosamine is not approved by the Food and Drug Administration (FDA) for medical use in humans. Since glucosamine is classified as a dietary supplement in the United States, evidence of safety is required by FDA regulations, but evidence of efficacy is not required so long as it is not advertised as a treatment for a medical condition. In 2004, the FDA declared there was insufficient evidence for supplement manufacturers to state that glucosamine was effective for treating arthritis, joint degeneration, or cartilage deterioration, a position remaining in effect as of 2018. In most of Europe, glucosamine is approved as a medical drug and is sold in the form of glucosamine sulfate. In this case, evidence of safety and efficacy is required for the medical use of glucosamine and several guidelines have recommended its use as an effective and safe therapy for osteoarthritis. The Task Force of the European League Against Rheumatism (EULAR) committee has granted glucosamine sulfate a level of toxicity of 5 in a 0-100 scale, and recent OARSI (Osteoarthritis Research Society International) guidelines for hip and knee osteoarthritis indicate an acceptable safety profile. By 2014, the OARSI did not recommend glucosamine for disease modification, and considered it "uncertain" for symptom relief, in knee osteoarthritis. In 2013, without admitting fault, manufacturer Rexall Sundown and NBTY agreed to pay up to to settle consumer claims related to the wording of certain claims on the packaging of glucosamine bottles sold at Costco under the Kirkland label. In August 2012, a class-action lawsuit was filed in New York claiming that 21st Century Healthcare, Inc. had falsely advertised that its "Glucosamine 750 Chondroitin 600 Triple Strength" dietary supplements would restore lost cartilage. In April 2013, a San Diego man launched a proposed class-action lawsuit in California Federal Court accusing Nutramax Laboratories, Walmart and Rite Aid of falsely advertising the effectiveness of glucosamine. Since glucosamine is a precursor for glycosaminoglycans, and glycosaminoglycans are a major component of cartilage, research has focused on the potential for supplemental glucosamine to beneficially influence cartilage structure and alleviate arthritis. Although its use as a supplement appears safe, the evidence does not support it being universally effective, as clinical trials have not provided results that support its efficacy in 100% of human subjects.