Safety and Effectiveness of Four-Factor Prothrombin Complex Concentrate in Special Populations with INR Below 2: A Post-Marketing Surveillance Study

We previously conducted a prospective, observational post-marketing surveillance study to assess the safety and effectiveness of four-factor prothrombin complex concentrate (4F-PCC) for rapid vitamin K antagonist (VKA) reversal in Japanese patients. This subgroup analysis compared the safety, especially thromboembolic events (TEEs), and effectiveness of 4F-PCC by stratifying patients into two subgroups according to baseline international normalized ratio (INR) levels with < 2.0 and ≥ 2.0. Of 1271 eligible patients, 215 (17.9%) had INR < 2.0 and 987 (82.1%) had INR ≥ 2.0. Overall baseline characteristics were similar between groups; age (74.0 years vs 74.0 years), body mass index (22.1 kg/m2 vs 21.9 kg/m2), ratio of inpatients (90.2% vs 88.7%), manifested atrial fibrillation (46.0% vs 48.8%). Median INRs at baseline were 1.72 (minimum 0.92, maximum 1.99) in the INR < 2.0 group and 2.95 (2.00, 27.11) in the INR ≥ 2.0 group. The most common reason for 4F-PCC administration was intracranial hemorrhage (67.0% vs 59.5%), and lesser gastrointestinal bleeding (0.9% vs 7.5%). After 4F-PCC administration (average doses 24.5 IU/kg INR < 2.0 group and 29.2 IU/kg INR ≥ 2.0 group), INRs were significantly reduced to 1.21 (− 28%) and 1.31 (− 68%), respectively, and resulted in hemostasis in a similarly rapid manner. The incidences of adverse drug reactions were 3.7% in each group. TEEs occurred in 4 (1.9%) patients in the INR < 2.0 group and 11 (1.1%) patients in the INR ≥ 2.0 group and were predominantly composed of stroke, while similar rates (67.0% vs 62.9%) of bleeding events post-anticoagulant resumption were observed between groups. This study supports the favorable tolerability and efficacy of 4F-PCC regardless of baseline INR (< 2.0 or ≥ 2.0), with a prompt reduction of INR and substantial hemostatic effectiveness in the real-world setting for patients requiring urgent VKA reversal, although no indicated 4F-PCC dose for VKA reversal exists for INR < 2.0 to date.