PassFinals
Pharmacology & Therapeutics

Anticoagulation (warfarin and DOACs)

Choose anticoagulation by indication, thrombotic risk, bleeding risk, renal function and patient preference; warfarin and direct oral anticoagulants have different monitoring, interactions and reversal pathways.

In a nutshell

Anticoagulant choice follows the indication and patient factors. DOACs are preferred for most eligible non-valvular AF and are options for much confirmed VTE; warfarin is required for mechanical valves and is used when DOACs are unsuitable. INR monitors warfarin, not DOAC activity. Major bleeding needs resuscitation, urgent specialist help and agent-specific reversal.

Classic presentation

A patient taking warfarin or a DOAC presents with bruising, gastrointestinal or intracranial bleeding, an unexpected INR, renal deterioration, a planned urgent procedure or recurrent thrombosis after missed doses.

Key points

  • Offer a DOAC for AF with CHA2DS2-VASc 2 or more and consider one for men with a score of 1, taking bleeding risk and preference into account; use a VKA if DOACs are unsuitable.
  • Mechanical heart valves require warfarin; do not switch these patients to a DOAC.
  • For confirmed proximal DVT or PE, treat for at least 3 months, then reassess recurrence risk, bleeding risk, provoking factors and patient preference.
  • INR is for warfarin. Routine anticoagulant-effect monitoring is not required for DOACs, but renal function, interactions, adherence and bleeding still need review.
  • Life-threatening warfarin bleeding requires urgent PCC plus vitamin K according to local haematology protocol; idarucizumab reverses dabigatran and NICE TA697 covers andexanet alfa for selected apixaban or rivaroxaban bleeds.
  • Do not use a fixed universal interruption or restart interval around procedures or bleeding; use the agent, renal function, procedural risk and thrombotic indication to drive the specialist plan.
  • Every patient needs written information, an anticoagulant alert card and clear advice on bleeding, missed doses, interactions, pregnancy, dental care and when to seek urgent help.

First-line investigation

Confirm the indication and last dose; check FBC, renal and hepatic function, and INR for warfarin. Use a calibrated drug-specific assay only when a DOAC level will change urgent management.

Management

Recognise major bleeding or thrombosis

  • Stabilise ABCDE, stop further doses, obtain the last-dose and renal history, control the source and call senior/haematology help for major bleeding or suspected intracranial haemorrhage.4,11,12

Identify the indication and safe drug

  • Use DOACs for most eligible non-valvular AF and many VTE pathways; retain warfarin for mechanical valves and when DOACs are unsuitable, and use specialist management for triple-positive antiphospholipid syndrome.1,2,3

Monitor the drug that is actually being used

  • Monitor warfarin with INR and review interacting drugs and illness; do not use INR as a DOAC assay, but review renal function, bleeding, adherence, interactions and dose suitability.5,14,4,13,6

Reverse only when the clinical criteria are met

  • Use PCC plus vitamin K for urgent warfarin reversal, idarucizumab for dabigatran, and NICE-criteria andexanet alfa for selected apixaban or rivaroxaban life-threatening bleeds; escalate edoxaban to haematology because there is no specific authorised antidote.10,4,11,7

Reassess duration, restart and safety

  • Review VTE duration at 3 months, ongoing AF anticoagulation at least annually and any restart after bleeding or procedures only after haemostasis and the thrombotic-versus-bleeding balance have been reviewed.2,1,15

Exam traps

  • INR is not a reliable test of DOAC activity; a normal INR does not exclude clinically important DOAC exposure.
  • Do not use a DOAC for a mechanical heart valve.
  • Do not give vitamin K alone when immediate warfarin reversal is required; PCC provides rapid factor replacement and vitamin K sustains reversal.
  • Andexanet alfa is not a universal antidote for every DOAC and is not used for edoxaban in current UK advice.
  • Do not stop or restart anticoagulation around surgery or bleeding using a memorised interval without checking the agent, renal function, indication and local specialist protocol.

Illustrations

Coagulation cascade and anticoagulant targetsDiagram of the clotting cascade highlighting the vitamin K-dependent factors targeted by warfarin and the single activated factor targeted by each DOAC.PassFinals · original
Warfarin versus DOAC reversal pathwaysSide-by-side diagram showing vitamin K and PCC reversing warfarin against idarucizumab and andexanet alfa reversing selected DOACs, with specialist escalation for edoxaban.PassFinals · original
Indication, monitoring and safety-netting mapFlow diagram linking atrial fibrillation, VTE and valve indications to drug choice, INR or renal monitoring, bleeding red flags and specialist review.PassFinals · original

Key sources

  1. NICE NG196: Atrial fibrillation, recommendations (NG196, current recommendations including anticoagulation choice and review)
  2. NICE NG158: Venous thromboembolic diseases, recommendations (NG158, current recommendations for VTE anticoagulation and duration)
  3. NHS England/MHRA: Inappropriate anticoagulation of patients with a mechanical heart valve (National Patient Safety Alert NatPSA/2021/006/NHSPS)
  4. MHRA: Direct-acting oral anticoagulants, bleeding risk and reversal agents (Drug Safety Update, 29 June 2020 with 2023 renal-impairment update note)
  5. NHS Specialist Pharmacy Service: Warfarin monitoring (Professional monitoring advice, current page)
  6. BNF: Apixaban (BNF medicine monograph for prescribing, renal dosing and interactions)
  7. BNF: Dabigatran etexilate (BNF medicine monograph for prescribing, renal dosing and interactions)
  8. BNF: Edoxaban (BNF medicine monograph for prescribing, renal dosing and interactions)
  9. BNF: Rivaroxaban (BNF medicine monograph for prescribing, renal dosing and interactions)
  10. NICE TA697: Andexanet alfa for reversing apixaban or rivaroxaban (TA697, last updated 15 January 2025)
  11. NHS Highland: Anticoagulant reversal guidance (UK NHS local therapeutic guideline; operational reversal pathway)
  12. NHS England: Delay in treatment with prothrombin complex concentrate (Patient-safety insight on timely PCC administration)
  13. BNF: Warfarin (BNF medicine monograph for prescribing, cautions, interactions and reversal)
  14. MHRA: Warfarin and other anticoagulants monitoring (Drug Safety Update, 22 October 2020)
  15. NHS: Anticoagulant medicines, considerations (Patient information on interactions, pregnancy and safety)

This page is exam revision material, not medical advice, and must not be used for patient care. Always check drug doses against the BNF and current guidance. Full disclaimer.