♦️ Anticoagulants We Encounter Most Often
In perioperative medicine, the anticoagulants that immediately come to mind are:
- Heparin
- Warfarin
- DOACs (Direct Oral Anticoagulants)
♦️ DOACs — Can You Recall All the Names?
While heparin and warfarin are familiar, there are currently four major DOACs on the market. Do you know both their generic and brand names?😅
- Dabigatran → Pradaxa®
- Apixaban → Eliquis®
- Rivaroxaban → Xarelto®
- Edoxaban → Savaysa® (Lixiana® in some countries, e.g., Japan/Europe)
🔷 From NOAC to DOAC
About a decade ago, these drugs were often referred to as NOACs (Novel Oral Anticoagulants). Since they are no longer “new,” the preferred term now is DOACs (Direct Oral Anticoagulants).
🔷 But What Does “Direct” Actually Mean?
Why the word “direct”? It implies that other anticoagulants act indirectly.
To clarify, let’s briefly review how heparin and warfarin work.
♦️ How Each Anticoagulant Works
🔷 Mechanism of Action — Heparin
Heparin does not directly block clotting factors. Instead, it binds to antithrombin III (AT-III), enhancing AT-III’s activity and leading to the inactivation of thrombin (factor IIa) and factor Xa.
👉 Importantly, heparin does not inhibit the synthesis of clotting factors.
🔷 Mechanism of Action — Warfarin
Warfarin works differently. It inhibits vitamin K epoxide reductase (VKOR), thereby blocking the recycling of vitamin K. Vitamin K is essential for the γ-carboxylation (activation) of vitamin K–dependent clotting factors (II, VII, IX, and X).
As a result, these clotting factors are synthesized but remain functionally impaired. Thus, warfarin acts indirectly, not by directly binding to the clotting factors.
🔷 Then, The Main Players: DOACs
And now to the DOACs themselves:
- Dabigatran → Direct thrombin (factor IIa) inhibitor
- Apixaban → Factor Xa inhibitor
- Rivaroxaban → Factor Xa inhibitor
- Edoxaban → Factor Xa inhibitor
Dabigatran binds directly to thrombin’s active site, while the other three bind directly to factor Xa, thereby blocking the prothrombinase complex and reducing thrombin generation.
📝 Summay / Take-Home Message
- Heparin: works indirectly via AT-III to inactivate IIa and Xa.
- Warfarin: works indirectly by inhibiting VKOR, reducing activation of factors II, VII, IX, X.
- DOACs: act directly on clotting factors.
- Dabigatran = thrombin inhibitor.
- Apixaban, rivaroxaban, edoxaban = factor Xa inhibitors. 👉 The key is in the name: “Direct” means direct binding to clotting factors.
🔗 Related articles
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