Oral anticoagulant drugs and the risk of osteoporosis: New anticoagulants better than old?

Several drugs have been associated with an increased risk of osteoporosis when used chronically. Coumarins (warfarin, acenocoumarol, phenprocoumon, and fluindione) are oral anticoagulants widely used for the prevention and treatment of arterial and venous thromboembolic diseases. These drugs are vitamin K antagonists that interfere with γ-carboxyglutamate formation, and consequently inhibit the carboxylation of glutamate residues of proteins that are synthesized in the bone. These effects on bone turnover and dietary restrictions in patients on anticoagulation are possible mechanisms inducing osteoporosis in coumarin users. However, conflicting evidence is available concerning the risk of osteoporosis and bone fractures in patients on treatment with these drugs. This risk is likely to be clinically relevant in long-term (more than 1 year) coumarin users. Novel direct oral anticoagulants, recently introduced in clinical practice, exert reduced interference on bone metabolism; however, limited in vitro and animal data are currently available, and their long-term effects will only become apparent in time.