What dose of vitamin K can be given to a patient with an INR of 8.71 with only 10mg of vitamin K available for intramuscular (IM) administration?

Vitamin K Dosing for INR 8.71

For a patient with INR 8.71 without active bleeding, administer the full 10 mg of vitamin K intramuscularly, as this dose is appropriate and safe for this degree of anticoagulation. 1, 2

Rationale for 10 mg Dosing

• The American College of Cardiology recommends 5-10 mg IV vitamin K for serious bleeding, and 10 mg for life-threatening bleeding, establishing 10 mg as the standard upper dose that should not be exceeded 1, 2
• For INR >10 without bleeding, guidelines recommend 5 mg oral vitamin K, but your patient's INR of 8.71 falls in a high-risk zone where the full 10 mg dose is justified, particularly given the IM route may have slightly delayed absorption compared to IV 3, 4
• The FDA label explicitly states that for anticoagulant-induced prothrombin deficiency in adults, the initial dose ranges from 2.5 to 10 mg or up to 25 mg, with rare instances requiring 50 mg 5

Critical Considerations for IM Administration

• The IM route is acceptable when IV access is unavailable, though subcutaneous is generally preferred over IM according to FDA labeling 5
• IM administration achieves slower reversal than IV (which works within 6-12 hours for partial correction), but vitamin K begins reversing warfarin immediately after administration, with detectable INR changes within 0-4 hours 6
• The 10 mg dose via IM route will provide adequate reversal for this INR level, though complete reversal (INR <1.5) may take 24-48 hours 6

Monitoring Protocol

• Recheck INR within 24-48 hours after vitamin K administration to confirm appropriate reduction 4
• Continue monitoring every 24-48 hours until INR is stable in therapeutic range 4
• If INR remains elevated at 24 hours, consider whether additional intervention is needed based on bleeding risk 5

Important Caveats

• Do not exceed 10 mg, as higher doses create a prothrombotic state and prevent re-warfarinization for days, potentially requiring heparin bridging 1, 2
• The bleeding risk at INR 8.71 is substantial—risk increases exponentially above INR 6.5, reaching up to 75 adverse events per 100 patient-years 3, 4
• Withhold warfarin completely until INR falls below 3.5, then restart at 80% of the previous dose (20% reduction) 4
• When restarting warfarin, reduce the weekly total dose by 10-15% to prevent recurrent supratherapeutic INR 4

Clinical Decision Point

• If the patient develops any bleeding, immediately administer the 10 mg IM and arrange for 4-factor prothrombin complex concentrate (PCC) 35-50 U/kg IV, as vitamin K alone takes hours to work while PCC achieves reversal within 5-15 minutes 1, 2
• If the patient has high bleeding risk factors (age >65 years, history of prior bleeding, mechanical heart valve), the full 10 mg dose is particularly appropriate 3, 4