💊 DOACs (Direct Oral Anticoagulants)

DOACs are a class of oral anticoagulant medications that directly inhibit specific clotting factors in the coagulation cascade. They are an alternative to warfarin for many indications.

Rivaroxaban and apixaban are direct factor Xa inhibitors, preventing the conversion of prothrombin to thrombin. Dabigatran is a direct thrombin inhibitor, preventing thrombin from converting fibrinogen to fibrin.

DOACs are primarily used for the prevention of stroke and systemic embolism in patients with non-valvular atrial fibrillation. They are also indicated for the treatment and secondary prevention of deep vein thrombosis (DVT) and pulmonary embolism (PE). Some DOACs are used for thromboprophylaxis after elective hip or knee replacement surgery.

Absolute contraindications include active pathological bleeding, severe uncontrolled hypertension, and significant liver disease associated with coagulopathy. They are also contraindicated in patients with mechanical prosthetic heart valves due to increased risk of thrombotic events. Caution is needed in severe renal impairment and in patients with conditions predisposing to bleeding.

The most significant adverse effect is bleeding, which can range from minor ecchymoses to life-threatening haemorrhage. Gastrointestinal upset, such as dyspepsia (especially with dabigatran), is also common. Hypersensitivity reactions are rare but can occur. There is a risk of thrombotic events if discontinued prematurely.

Routine coagulation monitoring is generally not required for DOACs, unlike warfarin. However, renal function should be assessed before initiation and periodically thereafter, as most DOACs are renally excreted. Liver function tests may also be considered, particularly in patients with pre-existing hepatic impairment.

Always check for active bleeding, severe renal or hepatic impairment, and concurrent medications that increase bleeding risk (e.g., NSAIDs, antiplatelets). Counsel patients on the importance of adherence, recognising signs of bleeding, and informing healthcare professionals about their medication. Emphasise that they should not stop taking the drug without medical advice.

DOACs have largely replaced warfarin for many indications due to their predictable pharmacokinetics and lack of need for routine INR monitoring. Dabigatran has a specific reversal agent (idarucizumab), while factor Xa inhibitors (apixaban, rivaroxaban) have andexanet alfa. Remember the contraindication in mechanical heart valves. Renal function is a key determinant for dose adjustment or choice of DOAC.

SBAs often focus on choosing the correct anticoagulant for a patient with atrial fibrillation, considering renal function and contraindications. Questions may also test knowledge of which DOACs are factor Xa inhibitors versus thrombin inhibitors. Recognising scenarios where DOACs are contraindicated (e.g., mechanical heart valves) is a common theme.