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Anticoagulant therapy: choice, duration and reversal

In most cases a DOAC is preferred over warfarin, except for fixed exceptions — a mechanical valve, moderate-severe mitral stenosis, antiphospholipid syndrome, very severe kidney failure and pregnancy; the length of treatment for thrombosis is set by its cause (3 months with a transient cause, extended for unprovoked thrombosis).

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Why it matters in the exam

Anticoagulant questions test the right choice. In venous thrombosis or atrial fibrillation without a mechanical valve, a DOAC (apixaban, rivaroxaban, edoxaban, dabigatran) is preferred. Warfarin remains the choice with a mechanical valve, moderate-severe mitral stenosis and antiphospholipid syndrome; in pregnancy LMWH is given, because warfarin is teratogenic and DOACs are not approved. Duration for thrombosis: 3 months when there was a major transient trigger (surgery, admission), extended treatment with no stop date for unprovoked thrombosis at low bleeding risk, and in cancer — LMWH or a DOAC for at least 6 months. The INR target for warfarin is 2–3, and 2.5–3.5 for a mechanical mitral valve.

The second part is bleeding and reversal. In life-threatening bleeding on warfarin, intravenous vitamin K and prothrombin complex concentrate (4-factor PCC) are given; when the INR exceeds 10 without any bleeding — hold warfarin and give vitamin K by mouth. Dabigatran is reversed with idarucizumab; factor Xa inhibitors with andexanet alfa or PCC. DOAC doses are adjusted for kidney function and age, and they interact with strong inhibitors and inducers of CYP3A4 and P-gp (for example rifampicin, carbamazepine). Most atrial fibrillation patients who stop warfarin before surgery need no heparin "bridging", which increases bleeding (details in the anaesthesia and surgery chapters).

Key points

• DOAC preferred, except mechanical valve, mitral stenosis, APS, pregnancy and very severe kidney failure.
• Thrombosis with transient cause: 3 months; unprovoked: extended; cancer: at least 6 months.
• Warfarin: INR 2–3; mechanical mitral valve 2.5–3.5.
• Reversal: vitamin K + PCC; idarucizumab for dabigatran; andexanet or PCC for Xa inhibitors.
• Pregnancy: LMWH.

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Sources

• CHEST Guideline and Expert Panel Report: Antithrombotic Therapy for VTE Disease, 2021 — Choice of anticoagulant and duration
• EHRA Practical Guide on the use of non-vitamin K antagonist oral anticoagulants, 2021 — Renal dosing, interactions and reversal
• Harrison's Principles of Internal Medicine, 21st edition (2022) — Antiplatelet, Anticoagulant, and Fibrinolytic Drugs

Sources are given for further reading; the text is written afresh and not copied from them.

Reviewed by the Examqo AI Professor · 2026-11-02. The text may contain errors; when in doubt, check the source.