Direct thrombin inhibitors include lepirudin and argatroban; they:

a. Require binding to antithrombin to provide their anticoagulant effect
b. Are usually monitored using the PT.
c. Are used when a patient develops heparin-induced thrombocytopenia
d. Bind all serine proteases

ANS: C
Direct thrombin inhibitors are used when a patient is suspected of having or confirmed to have heparin-induced thrombocytopenia. In this setting, LMWH is not substituted for unfractionated heparin. Direct thrombin inhibitors bind and inactivate free and sometimes clot-bound thrombin. As their name implies, they do not require binding to antithrombin to exert this effect. They are usually monitored using the PTT, although they also prolong the PT and the ACT.