Adolescents/Adults (≥12 years)
In adults, on average, one International Unit (IU) of BeneFIX per kilogram of body weight increased the circulating activity of factor IX by 0.8 ± 0.2 IU/dL (range 0.4 to 1.2 IU/dL). Use the following formula to estimate the dose with 0.8 IU/dL average increase of factor IX per IU/kg body weight administered:
number of factor IX IU required (IU) | = | body weight (kg) | × | desired factor IX increase (% of normal or IU/dL) | × | 1.3 (IU/kg per IU/dL) |
Children (<12 years)
In children, on average, one international unit of BeneFIX per kilogram of body weight increased the circulating activity of factor IX by 0.7 ± 0.3 IU/dL (range 0.2 to 2.1 IU/dL; median of 0.6 IU/dL per IU/kg). Use the following formula to estimate the dose with 0.7 IU/dL average increase of factor IX per IU/kg body weight administered:
number of factor IX IU required (IU) | = | body weight (kg) | × | desired factor IX increase (% of normal or IU/dL) | × | 1.4 (IU/kg per IU/dL) |
Doses administered should be titrated to the patient's clinical response. Patients may vary in their pharmacokinetic (e.g., half-life, recovery) and clinical responses to BeneFIX. Although the dose can be estimated by the calculations above, it is highly recommended that, whenever possible, appropriate laboratory tests, including serial factor IX activity assays, be performed.