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# Coagulation factor IX

Plasma-derived or recombinant factor IX infused to prevent and treat bleeding in haemophilia B.

Updated 2026-11-01

- Class: [Coagulation factor replacement and haemophilia agents](https://durgical.com/en/pharmacology/classes/coagulation-factor-replacement-and-haemophilia-agents/)
- Enzyme: Factor IX itself (the serine protease of the tenase complex)
- ATC code: B02BD04
- WHO Model List of Essential Medicines

✂**Factor IX itself (the serine protease of the tenase complex)**Coagulation factor IX

ⓘ The figure shows activated human factor IX (factor IXa); the small molecule in the crystal is p-aminobenzamidine, a laboratory inhibitor in the active site, not the drug.

**Target in 3D:** Factor IX itself (the serine protease of the tenase complex). PDB structure 1RFN (RCSB PDB, public domain). [View the structure at RCSB PDB](https://www.rcsb.org/structure/1RFN) · Drag to rotate · pinch to zoom

## Mechanism of action

Factor IX is a vitamin K-dependent zymogen. Activated by factor XIa or by tissue factor–VIIa, factor IXa, together with factor VIIIa, activates factor X. In haemophilia B, infused factor IX restores this step and allows thrombin to form.

- Infused factor IX replaces the missing zymogen
- It is activated to factor IXa
- IXa with VIIIa activates factor X
- Thrombin generation is restored

## Pharmacokinetics

**Half-life**
Extended half-life products allow less frequent infusions

## Indications

- Haemophilia B (Christmas disease): prophylaxis, treatment of bleeds and surgery [Haemophilia A and B →](https://durgical.com/en/conditions/haemophilia-a-and-b/)

## Adverse effects

### Common

- Infusion reactions
- Headache, nausea

### Serious (rare, important)

- Inhibitor development, sometimes with severe allergic reactions
- Thrombosis with older plasma-derived complex concentrates

## Contraindications

- Known severe allergy to the product

## Key interactions

**Antifibrinolytics (tranexamic acid, aminocaproic acid)**
With factor IX complex concentrates the risk of thrombosis increases

## What is monitored

- Factor IX activity levels
- Inhibitor testing and allergy during early exposures
- Clinical response

## Administration and safety

- Intravenous infusion after reconstitution; home infusion is common
- Pure factor IX is not the same as prothrombin complex concentrate; check the product before preparing it

## Nursing care

- Record the product name and lot number of every infusion
- Watch for allergic reactions during and after the infusion
- Teach the family to recognise joint and muscle bleeds early and to treat them quickly
- Report bleeding that does not respond as usual: it may mean an inhibitor

## Pregnancy and breastfeeding

Haemophilia B is rare in women; carriers with low levels may need it around delivery.

## Memory aid

«B for Nine», and IX is vitamin K-dependent like II, VII and X.

## Test yourself

Think of the answer, then tap the question to see it.

## Which haemophilia is treated with factor IX?

Haemophilia B.

## Is factor IX vitamin K-dependent?

Yes, like factors II, VII and X.

## Which drug interaction raises thrombosis risk with factor IX complex?

Antifibrinolytics such as tranexamic acid.

[Add to my cards (3)](https://durgical.app/estudiar/?add=/en/pharmacology/coagulation-factor-ix/)

## Related drugs

- [Coagulation factor VIII](https://durgical.com/en/pharmacology/coagulation-factor-viii/)
- [Tranexamic acid](https://durgical.com/en/pharmacology/tranexamic-acid/)

## Related conditions

- [Haemophilia A and B](https://durgical.com/en/conditions/haemophilia-a-and-b/)

[← Back to the class: Coagulation factor replacement and haemophilia agents](https://durgical.com/en/pharmacology/classes/coagulation-factor-replacement-and-haemophilia-agents/)

Educational content on how drugs work; not a prescribing guide and no substitute for a health professional's advice. No doses are given.

Sources: [Treatment of Hemophilia | Hemophilia | CDC](https://www.cdc.gov/hemophilia/treatment/index.html) (Centers for Disease Control and Prevention, 2026); Farmacología básica y clínica (Katzung), 16.ª ed., cap. 34 (McGraw Hill, 2025); [DailyMed - TRANEXAMIC ACID injection, solution](https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=6f033f1e-8c78-4c87-b870-6493944315ff) (DailyMed (U.S. National Library of Medicine), 2026); [ATCDDD - ATC/DDD Index](https://atcddd.fhi.no/atc_ddd_index/?code=B02BD04) (WHO Collaborating Centre for Drug Statistics Methodology, 2026).

## **Spotted a mistake?** We are always improving for the community. Tell us what is wrong and our team will review it. Report a mistake

Representative model, for educational purposes only.

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Source: https://durgical.com/en/pharmacology/coagulation-factor-ix/
License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/pharmacology/coagulation-factor-ix/