Chondroitin is a natural physiological compound that is synthesised endogenously and secreted by the chondrocytes. It is found in joint cartilage and connective tissue (including vessel walls).
Chondroitin is a mixture of high molecular weight glycosaminoglycans and disaccharide polymers composed of equimolar amounts of D-glucuronic acid, D-acetylgalactosamine and sulphates in 10–30 disaccharide units. (Glycos-aminoglycans are the substances in which collagen fibres are embedded in cartilage.)
Chondroitin absorbs water, adding to the thickness and elasticity of cartilage and its ability to absorb and distribute compressive forces. It also appears to control the formation of new cartilage matrix, by stimulating chondrocyte metabolism and synthesis of collagen and proteoglycan. Chondroitin also inhibits degradative enzymes (elastase and hyaluronidase), which break down cartilage matrix and synovial fluid, contributing to cartilage destruction and loss of joint function.
Chondroitin is claimed to be useful as a dietary supplement in combination with glucosamine in osteoarthritis and related disorders. Preliminary evidence suggests that chondroitin reduces the pain of osteoarthritis in the knee compared with placebo.
In a multicentre, randomised, double-blind, controlled study, involving 127 patients with osteoarthritis of the knee, 40 were treated with chondroitin sulphate oral gel 1200 mg daily, capsules 1200 mg daily or placebo for 3 months. Chondroitin (both formulations) significantly improved subjective symptoms, including joint mobility.
In a randomised, double-blind, placebo-controlled study, 80 patients with knee osteo-arthritis participated in a 6-month study and received either 2 × 400 mg chondroitin capsules twice a day or placebo. Symptoms of joint pain and time to perform a 20-metre walk were significantly reduced in the treated group, and there was a non-significant trend for the placebo group to use more paracetamol.
A 1-year, randomised, double-blind, controlled pilot study included 42 patients with symptomatic knee osteoarthritis. Patients were treated orally with 800 mg chondroitin sulphate or placebo. Chondroitin sulphate was well tolerated and significantly reduced pain and increased overall mobility. In addition, bone and joint metabolism stabilised in the treated patients, but not in those on placebo.
A meta-analysis that included seven trials of 372 patients taking chondroitin found that over 120 or more days, chondroitin was signifi-cantly superior to placebo with respect to the Lesquesne index and pain rating on a visual analogue scale (VAS). Pooling the data con-firmed these results, and showed at least 50% improvement in the treated versus the placebo patients. The authors concluded that further investigations using larger cohorts of patients for longer time periods were needed to prove the usefulness of chondroitin as a symptom-modifying agent in osteoarthritis.
A randomised, double-blind, double-dummy study compared the efficacy of chondroitin with diclofenac in 146 patients with knee osteoarthritis. During the first month, patients received either 3 × 50 mg diclofenac tablets daily plus 3 × 400 mg placebo sachets, or 3 × 400 mg chondroitin sachets daily plus 3 × 50 mg placebo tablets. From months two to three, the diclofenac patients were given placebo sachets alone, and the chondroitin patients were given chondroitin sachets. Both groups were treated with placebo sachets from months four to six. The diclofenac group showed prompt pain reduction, which disappeared after the end of treatment. In the chondroitin group, the therapeutic response appeared later, but lasted for up to 3 months after the end of treatment.
Chondroitin sulphate 1 g daily was investigated in a prospective, double-blind, placebo-controlled, multicentre clinical study in patients with femetotibial osteoarthritis. Treatment continued for 3 months and there was a 3-month post-treatment period. There was a trend towards efficacy, with good tolerability after 3 months’ treatment, and persistent efficacy 1 month post-treatment.
No problems have been reported.
Pregnancy and breast-feeding
No problems have been reported but there have not been sufficient studies to guarantee the safety of chondroitin in pregnancy and breastfeeding. Chondroitin is probably best avoided.
There are no known serious side-effects. How-ever, there are no long term studies assessing the safety of chondroitin. Rarely, gastrointestinal effects and headache have been reported. However, studies in animals have found significantly decreased haematocrit, haemoglobin, white blood cells and platelet count, and the risk of internal bleeding has been suggested.7 However, there are no reports of bleeding as a result of chondroitin use in humans.
Anticoagulants: Theoretically, chondroitin could potentiate the effects of anticoagulants.
Chondroitin is available in the form of capsules, typically containing 250–750 mg, often in combination with glucosamine. A review of two US products containing chondroitin showed that both had lower chondroitin levels than declared on the labels; this was also found for six out of 13 glucosamine and chondroitin combination products, all due to low chondroitin levels.
The dose is not established. Manufacturers tend to recommend 400–1200 mg daily.
Chondroitin appears to offer some pain relief in osteoarthritis. However, studies conducted so far have involved small numbers of subjects and have been short. Further research is required to establish the place of chondroitin as a supplement for osteoarthritis.
Dietary Supplements, Third Edition, by Pamela Mason, BSc, MSc, PhD, MRPharmS, published by Pharmaceutical Press, London, 2007.
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McNamara PS, Barr SC, Erb HN, et al. Hematologic, hemostatic and biochemical effects in dogs receiving an oral chondroprotective agent for thirty days. Am J Vet Res 1996; 57: 1390–1394.