All of the direct thrombin inhibitors increase the INR, albeit to a variable extent. When given in thera- peutic doses, argatroban has the greatest effect on the INR.227 This phenomenon complicates transition- ing from argatroban to vitamin K antagonists. To overcome this problem, the INR can be measured after stopping the argatroban infusion for several hours. Because holding argatroban may expose patients to a risk of thrombosis, another option is to monitor the vitamin K antagonist with a chromogenic factor X assay. In this setting, factor X levels,45% have been associated with INR values.2 when the effect of argatroban has been eliminated.228 Moni- toring factor X levels may be safer than aiming for an INR 4 when vitamin K antagonists are given in conjunction with argatroban.229,230 2.2 Reversal of Anticoagulant Effects There are no specific antidotes for direct thrombin inhibitors. Using inhibition of thrombin generation in whole blood recovered from a bleeding time incision as an index of activity, recombinant factor VIIa can reverse the anticoagulant effect of direct thrombin inhibitors in healthy volunteers.231 Although recom- binant factor VIIa reduces bleeding induced by direct thrombin inhibitors in animals, the usefulness of this agent in patients who are bleeding has not been established. www.chestpubs.org CHEST / 141 / 2 / FEBRUARY, 2012 SUPPLEMENT e37S 31. Shaughnessy SG, Young E, Deschamps P, Hirsh J. The effects of low molecular weight and standard heparin on cal- cium loss from fetal rat calvaria. Blood. 1995;86(4):1368-1373. 32. Linkins L-A, Dans AL, Moores LK, et al. Treatment and pre- vention of heparin-induced thrombocytopenia: antithrom- botic therapy and prevention of thrombosis, 9th ed: American College of Chest Physicians evidence-based clinical practice guidelines. Chest. 2012;141(2)(suppl):e495S-e530S. 33. Berkowitz SD. Treatment of established deep vein thrombo- sis: a review of the therapeutic armamentarium. Orthopedics. 1995;18(suppl):18-20. 34. 