DOAC

Direct oral anticoagulants, or DOACs, are a class of oral medications that inhibit specific factors in the coagulation cascade. They include direct thrombin inhibitors such as dabigatran, and direct factor Xa inhibitors such as rivaroxaban, apixaban, and edoxaban (and the Xa inhibitor betrixaban used for VTE prophylaxis in some settings).

DOACs generally provide fixed dosing with no routine coagulation monitoring. They differ in mechanism: dabigatran directly inhibits thrombin (factor IIa), whereas rivaroxaban, apixaban, and edoxaban inhibit factor Xa, reducing thrombin generation and clot formation. Many DOACs are substrates of P-glycoprotein and, for Xa inhibitors, of CYP3A4; these pathways create potential drug interactions. Renal function strongly influences clearance, particularly for dabigatran and some other agents.

DOACs are used for stroke prevention in nonvalvular atrial fibrillation, treatment of acute venous thromboembolism (deep vein thrombosis and pulmonary embolism), and routine prophylaxis after orthopedic surgery. They are favored over warfarin in many patients due to predictable effects and less monitoring, though they are not appropriate in all settings.

Initiation and dosing depend on the specific agent and renal function; dosing must be adjusted for impaired kidney function. There is no routine INR monitoring. In bleeding or prior to urgent surgery, reversal may be required. Do not use in patients with mechanical heart valves or moderate-to-severe mitral stenosis. Specific reversal agents exist: idarucizumab for dabigatran; andexanet alfa for factor Xa inhibitors; 4-factor PCC as a non-specific option when antidotes are unavailable.

Consider hepatic disease, pregnancy, and lactation; long-term use requires consideration of bleeding risk and patient factors. DOACs may still be contraindicated in severe hepatic impairment or in certain drug interactions; reversing decisions should be guided by local protocols.