Transitioning from Argatroban to Warfarin Therapy in Patients with Heparin-induced Thrombocytopenia

Argatroban, a direct thrombin inhibitor used for thromboprophylaxis or treatment in heparin-induced thrombocytopenia (HIT), is routinely monitored using the activated partial thromboplastin time (aPTT) yet also prolongs the international normalized ratio (INR). Peritransitional INRs, aPTTs, anticoagulant dosing patterns, and outcomes were evaluated in 165 HIT patients who were transitioned, without guidelines, from argatroban to warfarin therapy. Argatroban (median doses: 1.5-2.0 mcg/kg/min) and warfarin (median dose: 5 mg initially with 3.8 mg/day thereafter) overlapped a median 4 days. Median (5-95th percentile) aPTTs (in seconds) and INRs, respectively, were 59.8 (38.8-82.9) and 3.2 (1.7-7.0) during argatroban monotherapy, 68.6 (44.5-104) and 5.3 (2.4-16) maximally during cotherapy, 59.9 (38.7-92.2) and 4.0 (2.2-11.6) immediately before argatroban cessation during cotherapy, and 36.0 (25.6-60.2) and 2.3 (1.3-7.3) within a median 10-12 hours after argatroban cessation. Major bleeding occurred in 1 (0.6%...