Factor VIII (Specialist drug)

How it works

It replaces deficient coagulation factor VIII, which acts as a cofactor for activated factor IX to accelerate factor X activation and restore effective clot formation.

Prescribing in practice

• Inhibitory antibodies to factor VIII can develop, especially during early treatment, reducing efficacy, so response should be monitored and inhibitor testing performed if bleeding is not controlled.
• Allergic and hypersensitivity reactions can occur, and product choice (recombinant versus plasma-derived) should follow national recommendations.
• As some products are plasma-derived, viral-safety counselling and hepatitis A and B immunisation are advised.

Monitoring

Monitor factor VIII levels to guide and verify dosing, and perform inhibitor screening if the expected clinical or laboratory response is not achieved.

Counselling the patient

• Report a poor response to treatment or new difficulty controlling bleeds, as an inhibitor may have formed.
• Report any rash, wheeze or swelling during infusions promptly.
• Maintain treatment records and keep recommended hepatitis vaccinations current.

Evidence & guidelines

Factor VIII replacement is the established standard for haemophilia A in UK haemophilia centres, with prophylaxis and inhibitor monitoring underpinned by national haemophilia guidance.