Treatment and prophylaxis of bleeding in patients with haemophilia B (congenital factor IX deficiency).
For this indication, competent medicine agencies globally authorize below treatments:
20 - 60 [iU] per kg of body weight
From 20 To 60 [iU] per kg of body weight once every day
Dose and duration of the substitution therapy depend on the severity of the factor IX deficiency, on the location and extent of the bleeding and on the patient’s clinical condition.
The number of units of factor IX administered is expressed in International Units (IU), which are related to the current WHO standard for factor IX products. Factor IX activity in plasma is expressed either as a percentage (relative to normal human plasma) or in International Units (relative to an International Standard for factor IX in plasma).
One International Unit (IU) of factor IX activity is equivalent to that quantity of factor IX in one ml of normal human plasma.
The calculation of the required dosage of factor IX is based on the empirical finding that 1 International Unit (IU) factor IX per kg body weight raises the plasma factor IX activity by 1-2% of normal activity. The required dose is determined using the following formula:
Required units = body weight (kg) x desired factor IX rise (%) (IU/dl) x 0.8
The amount to be administered and the frequency of administration should always be oriented to the clinical effectiveness in the individual case.
In the case of the following haemorrhagic events, the factor IX activity should not fall below the given plasma activity level (in % of normal or in IU/dl) in the corresponding period. The following table can be used to guide dosing in bleeding episodes and surgery:
|Degree of haemorrhage / Type of surgical procedure||Factor IX level required (%) (IU/dl)||Frequency of doses (hours) / Duration of therapy (days)|
|Early haemarthrosis, muscle bleeding or oral bleeding||20-40||Repeat every 24 hours. At least 1 day, until the bleeding episode as indicated by pain is resolved or healing is achieved.|
|More extensive haemarthrosis, muscle bleeding or haematoma||30-60||Repeat infusion every 24 hours for 3-4 days or more until pain and acute disability are resolved.|
|Life threatening haemorrhages||60-100||Repeat infusion every 8 to 24 hours until threat is resolved.|
|Minor surgery including tooth extraction||30-60||Every 24 hours, at least 1 day, until healing is achieved.|
|Major surgery||80-100 (pre- and post-operative)||Repeat infusion every 8 to 24 hours until adequate wound healing, then therapy for at least another 7 days to maintain a factor IX activity of 30 to 60% (IU/dl).|
For long term prophylaxis against bleeding in patients with severe haemophilia B, the usual doses are 20 to 40 IU of factor IX per kilogram of body weight at intervals of 3 to 4 days. In some cases, especially in younger patients, shorter dosage intervals or higher doses may be necessary.
It is recommended to not exceed a maximal infusion rate of 5 ml/min.