Hæmofili B- patienter, der får faktor IX- præparater bør overvåges for at holde øje med udviklingen af neutraliserende antistoffer mod faktor IX (inhibitorer) (se Hvilke mulige bivirkninger).
Individuals with haemophilia B who receive factor IX preparations, should be monitored for the development of neutralising antibodies against factor IX (inhibitors) (see Possible side effects).