Pharmacology · Coagulation factor replacement and haemophilia agents

Coagulation factor VIII !

Plasma-derived or recombinant factor VIII infused to prevent and treat bleeding in haemophilia A.

Updated 2026-11-01

Class: Coagulation factor replacement and haemophilia agents
Target: Factor VIII itself (cofactor of factor IXa in the tenase complex)
ATC code: B02BD02
WHO Model List of Essential Medicines

Also called: antihaemophilic factor

Factor VIII itself (cofactor of factor IXa in the tenase complex)Coagulation factor VIII

The figure shows human coagulation factor VIII, the replaced protein itself.

Target in 3D: Factor VIII itself (cofactor of factor IXa in the tenase complex). PDB structure 2R7E (RCSB PDB, public domain). View the structure at RCSB PDB

Mechanism of action

Factor VIII circulates bound to von Willebrand factor. Thrombin activates it to factor VIIIa, which acts as the cofactor that speeds up factor X activation by factor IXa on the platelet surface. In haemophilia A the factor is missing or faulty; the infused concentrate temporarily restores its level, so thrombin and a stable clot can form.

Infused factor VIII replaces the missing protein
Thrombin activates it to factor VIIIa
VIIIa helps factor IXa activate factor X
Thrombin and a stable fibrin clot form

Pharmacokinetics

Distribution: Stays in plasma, bound to von Willebrand factor
Half-life: Short, so prophylaxis needs repeated infusions; extended half-life products exist

Indications

Haemophilia A: prophylaxis, treatment of bleeds and cover for surgery Haemophilia A and B →
Von Willebrand disease (intermediate-purity concentrates that contain von Willebrand factor) Von Willebrand disease →

Adverse effects

Common

Infusion reactions
Headache

Contraindications

Known severe allergy to the product or its components

Key interactions

Emicizumab: In patients on emicizumab, standard laboratory inhibitor tests do not work; specialised testing is needed

What is monitored

Factor VIII activity levels
Inhibitor testing when response falls
Clinical response of the bleed

Administration and safety

Intravenous infusion after reconstitution; patients and families can learn to infuse at home
Doses are calculated from weight and the factor level needed; products are not interchangeable without a new calculation

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 A is rare in women; female carriers may receive it around delivery when their levels are low.

Test yourself

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

What role does factor VIIIa play in coagulation?

Cofactor for factor IXa in activating factor X (tenase complex).

Why is a recombinant product preferred when available?

It avoids the residual risk of agents transmitted through pooled plasma.

What suggests an inhibitor?

Bleeding that no longer responds to the usual infusion.

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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: Treatment of Hemophilia | Hemophilia | CDC (Centers for Disease Control and Prevention, 2026); Farmacología básica y clínica (Katzung), 16.ª ed., cap. 34 (McGraw Hill, 2025); eEML - Electronic Essential Medicines List (World Health Organization, 2025); ATCDDD - ATC/DDD Index (WHO Collaborating Centre for Drug Statistics Methodology, 2026).

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Representative model, for educational purposes only.