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[Pharmacology](https://durgical.com/en/pharmacology/) · Class

# Coagulation factor replacement and haemophilia agents

Concentrates that replace a missing clotting factor (VIII in haemophilia A, IX in haemophilia B), plus emicizumab, which does factor VIII's job.

Updated 2026-11-01

## What they are

Plasma-derived or recombinant factor concentrates are infused to prevent bleeds (prophylaxis) or to treat them. Some patients develop inhibitors, antibodies that neutralise the infused factor. Emicizumab, a bispecific antibody, is a non-factor option for haemophilia A given under the skin.

## Mechanism of action

Factors VIII and IX form the intrinsic tenase complex on activated platelets, in which factor IXa, helped by factor VIIIa, activates factor X. Replacing the missing factor restores thrombin generation; emicizumab bridges factor IXa and factor X itself.

Target: Intrinsic tenase (factor IXa + VIIIa → factor X)

## Key points

- Haemophilia A = factor VIII deficiency; haemophilia B = factor IX deficiency; both X-linked
- Prolonged aPTT with normal PT
- Inhibitors (neutralising antibodies) are the main complication of replacement
- Mild haemophilia A and von Willebrand disease may respond to desmopressin
- Emicizumab plus activated prothrombin complex concentrate can cause thrombotic microangiopathy

## Drugs in this class

- [**Coagulation factor VIII** Plasma-derived or recombinant factor VIII infused to prevent and treat bleeding in haemophilia A. Factor VIII itself (cofactor of factor IXa in the tenase complex)](https://durgical.com/en/pharmacology/coagulation-factor-viii/)
- [**Coagulation factor IX** Plasma-derived or recombinant factor IX infused to prevent and treat bleeding in haemophilia B. Factor IX itself (the serine protease of the tenase complex)](https://durgical.com/en/pharmacology/coagulation-factor-ix/)
- [**Emicizumab** A bispecific antibody that bridges factors IXa and X, doing factor VIII's job. Given under the skin to prevent bleeds… Factor IXa and factor X (bridged by the antibody)](https://durgical.com/en/pharmacology/emicizumab/)

## Others in the class

- recombinant factor VIIa
- prothrombin complex concentrate
- von Willebrand factor concentrate

## Test yourself

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

## Which factor is missing in haemophilia B?

Factor IX.

## What is an inhibitor in haemophilia?

An antibody that neutralises the infused factor.

## Which test is prolonged in haemophilia?

The aPTT (the PT is normal).

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

Sources: Farmacología básica y clínica (Katzung), 16.ª ed., cap. 34 (McGraw Hill, 2025); [Treatment of Hemophilia | Hemophilia | CDC](https://www.cdc.gov/hemophilia/treatment/index.html) (Centers for Disease Control and Prevention, 2026); Goodman & Gilman's The Pharmacological Basis of Therapeutics, 14th ed., ch. 36 (McGraw Hill, 2023); [eEML - Electronic Essential Medicines List](https://list.essentialmeds.org/) (World Health Organization, 2025).

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