From the FDA Drug Label
2.4 Converting from or to apixaban
To switch from 2.5mg apixaban BID to heparin drip, stop apixaban and initiate heparin drip. The exact protocol for conversion is not explicitly stated in the label, but it is generally recommended to stop apixaban and start heparin when aPTT is <40 seconds for patients being converted from apixaban to heparin. However, this information is not directly provided in the label for the specific context of prothrombin mutation. 1
From the Research
To switch from apixaban 2.5mg BID to a heparin drip for a patient with prothrombin mutation, discontinue the apixaban and wait 24 hours before starting the heparin infusion, as this waiting period is necessary to minimize the risk of bleeding due to overlapping anticoagulant effects, as suggested by the pharmacokinetic properties of apixaban 2. When initiating the heparin drip, use a standard weight-based protocol, typically starting with a bolus of 80 units/kg followed by an initial infusion rate of 18 units/kg/hour.
- Monitor aPTT levels 6 hours after starting the infusion and adjust the rate to maintain the aPTT within the therapeutic range (typically 1.5-2.5 times the control value) 3.
- For patients with prothrombin mutation who have higher thrombotic risk, ensure there is minimal time without anticoagulation coverage.
- If the clinical situation requires immediate anticoagulation without the 24-hour waiting period, consider starting the heparin at a lower initial dose without a bolus and monitor closely for bleeding complications, taking into account the effects of apixaban on thrombin generation parameters 2 and the relationship between anti-factor Xa activity and aPTT 4, 5. The most recent and highest quality study on anticoagulation monitoring 5 highlights the importance of adapting laboratory testing strategies to the changing anticoagulation landscape, which supports the use of aPTT for monitoring heparin therapy in patients transitioning from oral factor Xa inhibitors like apixaban.