Anticoagulant & Rodenticide (Warfarin & Superwarfarin) Poisoning

Overview & definition

The vitamin-K-antagonist anticoagulants — the therapeutic warfarin and the superwarfarin long-acting anticoagulant rodenticides (the LAARs — the brodifacoum, the bromadiolone, the difenacoum, the difethialone) — produce the coagulopathy by the inhibition of the vitamin-K-epoxide reductase (the VKORC1). The warfarin is the manageable (the half-life the 40 h); the superwarfarin is the prolonged and the dangerous (the half-life the weeks to the months) and the demands the weeks-to-the-months of the vitamin K.[1][1]

The mechanism

The warfarin and the superwarfarin inhibit the vitamin-K-epoxide reductase (the VKORC1) — the enzyme that the recycles the vitamin K (the epoxide → the active hydroquinone). Without the active vitamin K, the gamma-carboxylation of the vitamin-K-dependent clotting factors (the II / prothrombin, the VII, the IX, the X) and the natural anticoagulants (the proteins C and S) is the impaired — the factors the produced but the non-functional (the no the calcium-binding, the no the activation).[1][1]

The warfarin versus the superwarfarin

• The warfarin — the therapeutic, the half-life the 40 hours. The acute overdose or the supratherapeutic. The coagulopathy the manageable over the days; the vitamin K the several days.[1]
• The superwarfarin (the LAARs — the brodifacoum, the bromadiolone) — the rodenticide. The half-life the weeks to the months (the hepatic accumulation, the high lipid solubility). The prolonged, the severe coagulopathy. The demands the weeks-to-the-months of the high-dose vitamin K (the sometimes the months to the year). The risk of the relapse if the vitamin K the stopped early.[1]

The clinical

• The bleeding — the any site. The mucosal (the epistaxis, the gingival), the GI (the melaena, the haematemesis), the genitourinary (the haematuria), the intracranial (the dangerous), the soft-tissue (the bruising, the haematoma).[1][1]
• The coagulation — the PT/INR the markedly prolonged (the INR often the above 10; the sometimes the unmeasurable). The aPTT the prolonged (the less). The factors the reduced.
• The history — the occupational (the pest-control), the intentional (the self-harm, the Munchausen, the sabotage), the accidental (the child, the pet bait). The "the unexplained coagulopathy" — the suspect the superwarfarin.[1]

The investigation

• The PT/INR — the markedly prolonged; the thrombin time the normal (the distinguishes from the dabigatran / the heparin). The factors (the II, VII, IX, X the reduced).[1]
• The serum warfarin / the brodifacoum level (the qualitative; the not the routine but the confirmatory for the superwarfarin).
• The FBC (the anaemia from the bleeding), the platelet (the normal — the distinguishes from the thrombocytopenia), the cross-match (the transfusion).[1][1]
• The imaging (the CT brain for the intracranial; the imaging for the occult bleeding).[1]

Treatment

1. The active, the life-threatening bleeding — the immediate reversal.[2][1][1]

• The 4-factor prothrombin-complex concentrate (the PCC) IV (the 25 to 50 units/kg) — the fastest, the most-effective; the reconstitutes the factors immediately. The preferred over the FFP (the faster, the smaller-volume, the more-effective).[2]
• The IV vitamin K1 (the phytomenadione, the 10 mg IV slowly) — the restores the factor SYNTHESIS (the onset the 6 to 12 h; the peak the 24 h). The given WITH the PCC (the PCC the immediate, the vitamin K the sustained).[1]
• The FFP (the 15 mL/kg) if the PCC the unavailable. The larger-volume, the slower.[1]
• The transfusion (the red cells for the anaemia; the platelets if the thrombocytopenia).[1]

2. No the active bleeding, the INR elevated — the vitamin K.[1][1]

• The oral vitamin K1 (the 1 to 5 mg) for the INR the mildly elevated; the IV for the higher. The hold the warfarin.
• The monitor the INR; the titrate.[1]

3. The superwarfarin — the prolonged vitamin K.[1]

• The high-dose vitamin K1 (the oral, the sometimes the IV; the 50 to 100 mg/day) for the weeks to the months — the superwarfarin the half-life the weeks-to-the-months. The relapse if the stopped early. The monitor the INR throughout. The sometimes the year-long course.[1]
• The psychosocial (the intentional — the self-harm, the Munchausen).[1]

The Direct Oral Anticoagulants (the DOACs) — the dabigatran, the apixaban, the rivaroxaban, the edoxaban

The direct oral anticoagulants (the DOACs) — the direct thrombin inhibitor (the dabigatran) and the direct factor-Xa inhibitors (the apixaban, the rivaroxaban, the edoxaban) — the increasingly the supplant the warfarin (the no the routine the monitoring, the predictable the pharmacokinetics, the fewer the interactions). The DOAC overdose (the accidental, the supratherapeutic, the intentional, the renal the failure) the produces the bleeding the indistinguishable from the warfarin — the mucosal, the GI, the intracranial. The reversal the agent-specific: the idarucizumab (the Praxbind) for the dabigatran; the andexanet alfa (the Andexxa / the Ondexxya) for the apixaban / the rivaroxaban; the 4-factor PCC (the 50 IU/kg) for the apixaban / the rivaroxaban if the andexanet the unavailable; the FFP the no the role (the ineffective for the DOAC).[3][4][9]

The DOAC the half-life the 5-17 h (the shorter the warfarin); the renal the dabigatran (the 80 per cent the renal — the dialysis the removes), the mixed the apixaban / the edoxaban (the 25-50 per cent the renal), the hepatic-biliary the rivaroxaban (the 33 per cent the renal, the 66 per cent the hepatic). The renal the failure the prolongs the half-life (the dabigatran the 30 h the dialysis-dependent) — the dialysis the removes the dabigatran (the 50-60 per cent; the NOT the apixaban / the rivaroxaban — the protein-bound the 87-95 per cent).[6][9]

[1]

The DOAC — the laboratory (the drug-specific, the NOT the INR)

The PT/INR and the aPTT the unreliable the DOAC — the apixaban the often the normal the PT; the dabigatran the variably the prolongs the aPTT. The DOAC the NOT the monitored (the predictable the pharmacokinetics — the no the routine the level). The DOAC-specific the assays the required for the confirmatory:[4][6]

• The dabigatran — the dilute thrombin time (the dTT) or the ecarin clotting time (the ECT); the sensitive the quantitative. The standard the thrombin time the too the sensitive (the near-infinite the high the concentration). The anti-IIa the calibrated.
• The apixaban / the rivaroxaban / the edoxaban — the anti-Xa the calibrated (the drug-specific the calibration — the apixaban the anti-Xa ≠ the rivaroxaban the anti-Xa). The NOT the heparin the anti-Xa (the over-estimates the DOAC). The level > 50 ng/mL the bleeding the threshold.
• The "the < 50 ng/mL" the rule — the if the DOAC the level < 50 ng/mL AND the no the life-threatening the bleed, the supportive the management (the no the antidote the required). The drug the below the therapeutic the range. [1]

The DOAC reversal — the agents (the idarucizumab, the andexanet, the PCC)

1. The idarucizumab (the Praxbind) — the dabigatran

The idarucizumab — the humanised the monoclonal-antibody the Fab fragment — the binds the dabigatran with the 350-fold the higher the affinity than the dabigatran the binds the thrombin. The 1:1 the stoichiometric the binding; the immediate the neutralisation (the within the minutes). The 5 g IV (the 2 × 2.5 g the vials, the 5 min the apart; the two the boluses or the rapid the infusion). The peak the reversal the within the 15 min. The dialysis the not the required (the idarucizumab the removes the dabigatran from the circulation; the extravascular the dabigatran the redistributes — the occasionally the second the dose).[3]

The RE-VERSE AD the trial (the Pollack et al. 2017) — the prospective the single-arm the cohort of the 503 the dabigatran-treated the patients with the serious the bleeding or the requiring the urgent the procedure. The idarucizumab 5 g IV the reversed the dabigatran the anticoagulant the activity in the 88-98 per cent the immediately (the dTT the normalised; the ECT the normalised). The thrombotic the events the 4.8 per cent (the 90-day); the 19 per cent the 90-day the mortality (the serious-the-bleed the population).[3]

2. The andexanet alfa (the Andexxa / the Ondexxya) — the apixaban, the rivaroxaban

The andexanet alfa — the recombinant the modified the factor Xa — the catalytically the inactive (the serine-the-protease the domain the mutation) but the retains the Gla-domain the binding. The acts as the decoy — the binds the apixaban / the rivaroxaban (the competitive the sequestration) the AND the releases the tissue-factor-pathway the inhibitor (the TFPI) → the enhanced the thrombin the generation. The 2-min the onset. The low dose (the 400 mg IV bolus at the 30 mg/min then the 4 mg/min × 120 min) for the apixaban the any-dose or the rivaroxaban ≤ 10 mg, the LAST the dose > 8 h; the high dose (the 800 mg bolus then the 8 mg/min × 120 min) for the rivaroxaban > 10 mg or the unknown, the LAST the dose < 8 h. The andexanet the also the reverses the enoxaparin (the LMWH).[4][5]

The ANNEXA-4 the trial (the Connolly et al. 2019) — the single-arm the prospective of the 352 the patients with the apixaban / the rivaroxaban the major the bleeding. The andexanet the reduced the anti-Xa the activity by the 92 per cent; the excellent the haemostasis the 82 per cent at the 12 h. The thrombotic the events the 10 per cent (the 30-day) — the higher the than the idarucizumab. The rebound the anti-Xa the activity after the infusion the ends (the unbound the drug the redistributes) — the re-bleeding the risk.[4]

The ANNEXA-A and the ANNEXA-R (the Siegal et al. 2015) — the randomised the placebo-the-controlled (the healthy the older the volunteers). The andexanet the immediately the reversed the apixaban (the ANNEXA-A) and the rivaroxaban (the ANNEXA-R) the anti-Xa the activity; the no the serious the adverse.[5]

3. The 4-factor PCC — the apixaban, the rivaroxaban, the edoxaban (the if the andexanet the unavailable)

The 4-factor PCC (the 50 IU/kg IV) — the surrogate the reversal for the factor-Xa the inhibitors when the andexanet the unavailable (the expensive, the limited the supply, the not the stocked the all the hospitals). The mechanism: the overwhelming the factor the load (the II, the VII, the IX, the X — the more the factor than the inhibitor the can the bind). The 50 IU/kg the typical (some the 25-50 IU/kg). The improves the thrombin the generation the surrogate (the ETP) the NOT the anti-Xa (the does NOT the neutralise the drug — the overwhelms).[7][9]

The the andexanet versus the PCC the debate — the andexanet the more the effective (the true the neutralisation) but the higher the thrombosis and the expensive; the PCC the cheaper, the stocked, the modest the effect but the widely the used. The 2024 the ACC/AHA the guidance the prefer the andexanet for the apixaban / the rivaroxaban the life-threatening the bleed; the 4-factor PCC the 50 IU/kg the if the andexanet the unavailable.[1]

The warfarin reversal — the detailed protocol (the 4-factor PCC + the vitamin K + the FFP)

The warfarin (and the superwarfarin) the reversal the two-pronged: the immediate the factor the repletion (the 4-factor PCC; the FFP the alternative) PLUS the sustained the factor the synthesis (the IV vitamin K1 10 mg). The PCC the alone the insufficient — the factors the short the half-life (the 6 h for the factor VII) — the INR the rebounds the 12-24 h the without the vitamin K. The vitamin K the alone the too the slow (the onset the 6-12 h) for the active the bleed. The both the together.[2][7]

The 4-factor PCC the dosing — the INR-based (the weight-based):

• The INR 2-4 — the 25 IU/kg (the Beriplex P / the Kcentra; the Octaplex; the Cofact; the max the 2,500 IU).
• The INR 4-6 — the 35 IU/kg (the max the 3,500 IU).
• The INR > 6 — the 50 IU/kg (the max the 5,000 IU). [1]

The 4-factor PCC (the Beriplex P / the Kcentra; the Octaplex; the Cofact) the contains the factors II, the VII, the IX, the X (the 4-factor; the proteins C and S the variable). The reconstitutes the factors the immediately (the within the minutes). The INR the recheck the 30 min the post — the repeat the dose if the INR the still the above the target.[2][8]

The vitamin K1 (the phytomenadione) the 10 mg IV — the SLOWLY (the over the 20-30 min; the NOT the bolus — the anaphylactoid). The restores the factor the synthesis (the gamma-carboxylation). The onset the 6-12 h; the peak the 24 h; the full the effect the 48-72 h. The given the WITH the PCC (the PCC the immediate; the vitamin K the sustained — the prevents the rebound).[1][1]

The FFP (the 15 mL/kg; the 4 units) — the if the PCC the unavailable. The larger the volume (the 1 L the typical), the slower (the thawing, the infusion the time), the less the effective (the factor the concentration the low; the factor VII the labile). The risk the TRALI, the TACO, the pathogen the transmission. The PCC the preferred the whenever the available.[2][1]

The reversal agent — the comparison (the DOAC and the warfarin)

[1]

The reversal algorithm — by the drug and the bleeding severity

[1]

The time-to-offset — the drug still present after the reversal

The DOAC the still the present after the reversal — the idarucizumab the binds the dabigatran in the circulation (the extravascular the dabigatran the redistributes; the occasionally the second the dose the 12-24 h). The andexanet the short the half-life (the 1 h); the infusion the ends → the rebound the anti-Xa (the unbound the drug the redistributes from the extravascular). The PCC the factors the short the half-life (the factor VII the 6 h) — the INR the rebounds the 12-24 h. The the patient the still the anticoagulated — the monitor, the re-assess, the re-dose.[3][4][1]

The special situations

• The intracranial the haemorrhage (the ICH) — the most-feared. The immediate the reversal (the PCC + the vitamin K for the warfarin; the idarucizumab / the andexanet for the DOAC). The PCC the faster than the FFP (the improved the outcome in the ICH — the Steiner the 2016 the INCH). The systolic the BP < 140. The neurosurgery. The thrombotic the risk the managed the post.[8][1]
• The massive the GI the bleed — the source the control (the endoscopy / the colonoscopy / the angioembolisation). The reversal (the PCC for the warfarin; the idarucizumab / the andexanet for the DOAC). The transfusion (the RBC, the platelet if the anti-platelet).
• The peri-operative / the urgent the surgery — the DOAC the delay the 24-48 h (the 2 × the half-life); the reversal if the urgent. The warfarin the PCC + the vitamin K.
• The traumatic the bleed — the massive the transfusion the protocol; the tranexamic the acid (the 1 g IV); the reversal of the anticoagulant. The trauma the team; the damage-control the surgery.
• The pregnancy — the warfarin the teratogenic (the first the trimester); the DOAC the contraindicated. The heparin / the LMWH the preferred. The reversal the heparin the protamine; the LMWH the protamine the partial.
• The renal the failure — the dabigatran the accumulates (the 80% the renal); the dialysis the removes. The apixaban / the rivaroxaban the protein-bound the dialysis the ineffective. The idarucizumab for the dabigatran the dialysis-dependent.

Prognosis

The warfarin overdose is the survivable with the vitamin K and the PCC; the mortality driven by the bleeding (the intracranial). The superwarfarin is the prolonged (the weeks-to-the-months) but the survivable with the prolonged vitamin K. The relapse the risk if the vitamin K the stopped early. The Munchausen / the sabotage the recurring.[1][1][1]

Red flags

[1] [1]

Clinical pearls

Key trials and evidence

[1] [1] [1] [1] [1] [1] [1] [1]

References

1. [1]Caravati EM, et al. Long-Acting Anticoagulant Rodenticide (Superwarfarin) Poisoning: A Review of Its Historical Development, Epidemiology, and Clinical Management Transfus Med Rev, 2015.PMID 26239439
2. [2]Hunt BJ, et al. Prothrombin complex concentrate for vitamin K antagonist reversal in acute bleeding settings: efficacy and safety Expert Rev Hematol, 2019.PMID 31159607
3. [3]Pollack CV, Reilly PA, Eikelboom JW, et al. [Prevalence and predisposing factors of methicillin-resistant Staphylococcus aureus in long-term care facilities. An international view] Orv Hetil, 2016.PMID 27346474
4. [4]Connolly SJ, Milling TJ Jr, Eikelboom JW, et al. Atomic-Level Customization of 4 in. Transition Metal Dichalcogenide Multilayer Alloys for Industrial Applications Adv Mater, 2019.PMID 31157462
5. [5]Siegal DM, Curnutte JT, Connolly SJ, et al. In vivo NAD assay reveals the intracellular NAD contents and redox state in healthy human brain and their age dependences Proc Natl Acad Sci U S A, 2015.PMID 25730862
6. [6]Cuker A, Burnett A, Triller D, Crowther M, Ansell J, Van Cott EM, et al. An overview of neural networks for drug discovery and the inputs used Expert Opin Drug Discov, 2018.PMID 30449189
7. [7]Sarode R, Milling TJ Jr, Refaai MA, Mangione A, Schneider A, Durn BL, Goldstein JN An indicator of probable semicircular canal dehiscence: ocular vestibular evoked myogenic potentials to high frequencies Otolaryngol Head Neck Surg, 2013.PMID 23674567
8. [8]Steiner T, Poli S, Griebe M, Hüsing J, Hajda J, Pabst W, et al. Maternal postpartum high-dose vitamin D3 supplementation (6400 IU/day) or conventional infant vitamin D3 supplementation (400 IU/day) lead to similar vitamin D status of healthy exclusively/fully breastfeeding infants by 7 months of age Evid Based Med, 2016.PMID 26759149
9. [9]Tomaselli GF, Mahaffey KW, Cuker A, Dobesh PP, Doherty JU, Eikelboom JW, et al. Intra-auricular modification of facelift incision decreased the risk of Frey syndrome Tzu Chi Med J, 2019.PMID 31867256