Glucosamine Warfarin

Vitamin K antagonists, such as dicoumarol (8.61, a natural product) and warfarin (8.62), are used as anticoagulants in human therapy (thrombosis, atherosclerosis) and as rat poisons that lead to internal bleeding and death in rodents. Heparin, a polysaccharide consisting of 2-0-sulfonated glucuronic acid and 2-N,6-0-disulfonated glucosamine, is also a widely used anticoagulant, but its effect is connected not with Vitamin K but with enzyme inhibition. 

Glucosamine sulfate may increase the International Normalized Ratio (INR) in patients taking warfarin, increasing the risk for bruising and bleeding. The mechanism is not well understood and may be dose-related as increases in INR have occurred when the glucosamine dose was increased. Until more is known, the combination should be avoided or very carefully monitored. 

Interactions of glucosamine with warfarin (29,30) and acenocoumarol (31) have been described. 

Scott GN. Interaction of warfarin with glucosamine-chondroitin. Am J Health Syst Pharm 2004 61(11) 1186. 

Han cartilage or tendons. Glucosamine, in large doses, can increase insulin requirements in diabetics. Chondroitin increases the likelihood of relative overdose with warfarin, probably by competition for plasma protein binding sites and increase in free warfarin concentrations. 

A few reports surest that glucosamine with or without chondroitin may increase the HSR in patients taking warfarin. In contrast, one case of a decreased HSR has been reported when glucosamine was given with acenocoumarol. 

Scott GN. Interaction of warfarin widi glucosamine—chcndioitiiL Am J Heallh-Syst Pharm (2004)61, 1186. 

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