PB1188 - Use of DOAC-Stop to guide warfarin therapy in patients receiving argatroban

Background: The direct thrombin inhibitor argatroban prolongs the PT and APTT. During warfarinisation with target INR 2.0-3.0, guidance suggests continuing argatroban until the INR is >4. Guidance for higher target INR bridging is lacking. Pre-treatment of plasma with the activated charcoal-based reagent DOAC-Stop can be used to remove DOACs for coagulation testing, but scant literature exists on use in argatroban-treated patients.

Aims: To evaluate DOAC-stop INR during argatroban treatment.

Methods: We present a case where INR testing in presence of DOAC-Stop was used to guide re-warfarinisation with a target INR of 3.0-4.0.

Results: A 70-year-old female with a ball-and-cage mechanical mitral valve (target INR 3.0-4.0) and history of HITT was admitted to intensive care with urosepsis. Warfarin requirements fluctuated (dose between 3-10mg), her INR became subtherapeutic for prolonged periods necessitating argatroban bridging. Due to previous stroke on therapeutic warfarin, risk of argatroban with INR < 2.5 was deemed high, thus DOAC-Stop INR was used to guide warfarin dosing without cessation of argatroban. DOAC-Stop added to plasma reduced both APTT and TT indicating neutralisation of argatroban. INRs were measured during continuous argatroban infusion in presence and absence of DOAC-Stop. Standard INR>4.0 corresponded with DOAC-Stop INR ranging between 1.8 and 2.8 (Figure 1). The variable effect of argatroban interaction with warfarinised plasma on INR in absence of DOAC-Stop meant that using an arbitrary INR cutoff would have resulted to under-warfarinisation, while the INR in presence of DOAC-Stop correlated well with post -argatroban INR.

Conclusion(s): Our case provides an example of DOAC-Stop use to guide anticoagulation in patients receiving argatroban. To date only one case report has been published describing this practice, in antiphospholipid syndrome. Our study has demonstrated that a rule of awaiting an INR >4.0 may lead to premature argatroban cessation. Larger scale studies are warranted to explore the use of DOAC-Stop in patients receiving argatroban.