NOAC vs DOAC: Nomenclature Clarification
NOAC and DOAC refer to the same class of medications—there is no clinical difference between them, only terminology. Both terms describe oral anticoagulants like dabigatran, rivaroxaban, apixaban, edoxaban, and betrixaban that directly inhibit specific coagulation factors (Factor IIa or Factor Xa) rather than working through vitamin K antagonism 1.
The Terminology Evolution
The confusion stems from multiple competing terms used to describe this drug class:
- NOAC originally stood for "Novel Oral Anticoagulants" or "New Oral Anticoagulants" 1
- Some later proposed redefining NOAC as "Non-VKA Oral Anticoagulants" to maintain the familiar abbreviation 1
- DOAC stands for "Direct Oral Anticoagulants" 1
- Other less common terms included TSOAC (Target-Specific Oral Anticoagulants) 1
Why DOAC is the Preferred Term
The International Society on Thrombosis and Haemostasis (ISTH) recommends using "Direct Oral Anticoagulant (DOAC)" as the standard terminology and suggests avoiding the term NOAC entirely 1.
Key Reasons for This Recommendation:
Safety concerns: NOAC written in medical records has been misinterpreted as "No AntiCoagulation," potentially resulting in patients not receiving critical anticoagulant therapy 1
Descriptive accuracy: The term "direct" accurately describes the mechanism of action—these drugs directly inhibit a single specific coagulation factor (either Factor IIa or Factor Xa), unlike vitamin K antagonists that indirectly reduce synthesis of multiple clotting factors 1
No longer "novel": These medications are no longer new, making "novel" or "new" increasingly inappropriate 1
Scientific appeal: Defining a drug class by what it is (direct-acting) is more scientifically sound than defining it by what it is not (non-VKA) 1
Survey Results Supporting DOAC:
In a 2015 ISTH survey of 77 thrombosis and anticoagulation experts 1:
- 89.6% felt consensus on terminology was needed 1
- When asked about acceptable terms, DOAC received the most votes (58.4%) 1
- When asked to pick the single best term, DOAC received 29.9%, NOAC (non-VKA) received 28.6%, and TSOAC received 23.4% 1
- 54.7% felt NOAC had safety implications that should limit its use 1
Clinical Implications
In practice, when you encounter either term in the literature or clinical documentation, understand they refer to the identical drug class 1. The medications include:
- Direct thrombin inhibitor (Factor IIa): Dabigatran 1
- Direct Factor Xa inhibitors: Rivaroxaban, apixaban, edoxaban, betrixaban 1
When Mechanism Matters:
The ISTH recommends specifying the drug's mechanism of action (direct FXa inhibitor vs. direct thrombin inhibitor) when clinically relevant, such as when selecting appropriate coagulation laboratory testing or considering reversal strategies 1.
Common Pitfalls to Avoid
- Do not use NOAC in medical documentation due to the documented risk of misinterpretation as "No AntiCoagulation" 1
- Do not assume all DOACs are interchangeable—while they share similar properties, they have different pharmacokinetics, dosing schedules, and specific indications 2
- Remember these are NOT appropriate for mechanical heart valves or moderate-to-severe mitral stenosis—vitamin K antagonists remain the standard for these conditions 2, 3, 4, 5