Factor VIII (antihaemophilic Factor)

Uses

Treatment and prophylaxis of haemorrhagic episodes in patients with haemophilia A, Prophylaxis in severe haemophilia A

Factor VIII (antihaemophilic Factor) is also used to associated treatment for these conditions: Hemorrhagic episodes

How Factor VIII (antihaemophilic Factor) works

The human antihemophilic factor replaces the coagulation factor VIII. It acts as a co-factor for factor IX to activate factor X in the intrinsic pathway of blood coagulation.

Dosage

Factor VIII (antihaemophilic Factor) dosage

Intravenous (Adult)-

Treatment and prophylaxis of haemorrhagic episodes in patients with haemophilia A:Dosage is individualised based on coagulation tests performed before treatment and at regular intervals during treatment. Generally, 1 IU/kg will increase circulating factor VIII levels by about 2 IU/dL. Recommended doses vary according to the preparation used.

Suggested doses: Mild-moderate haemorrhage (increase to 20-30% of normal): Usually with a single dose of 10-15 IU/kg;

More serious haemorrhage or minor surgery (increase to 30-50% of normal): Usual initial dose of 15-25 units/kg followed by 10-15 IU/kg every 8-12 hr if required;

Severe haemorrhage or major surgery (increase to 80-100% of normal): Usual initial dose of 40-50 IU/kg followed by 20-25 IU/kg every 8-12 hr. Refer to individual product information for further dosing details.

Prophylaxis in severe haemophilia A:10-50 IU/kg every 2-3 days, as needed.

Intravenous: Treatment and prophylaxis of haemorrhagic episodes: If refrigerated, warm dried concentrate and diluent to room temperature before reconstitution.

Side Effects

Allergic reactions e.g. chills, chest tightness, fever, headache, hyperfibrinogenaemia, jittery feeling, lethargy, nausea, vomiting, somnolence, stinging at infusion site, stomach discomfort, tingling, urticaria, vasomotor reactions with rapid infusion.

Toxicity

The highest toxicity is the risk of viral hepatitis transmition as well as intravascular hemolyisis can occur if large or frequent doses are used in blood groups A, B or AB.

Precaution

Risk of intravascular haemolysis in patients with blood groups A, B, or AB receiving high doses or repeated doses of factor VIII preparations. Risk of transmission of some viral infections especially hepatitis B and C. Dose requirement may vary in patients with factor VIII inhibitors; thus optimal treatment should be based on clinical response. Monitor platelet counts regularly during treatment.

Interaction

Allergic reactions e.g. chills, chest tightness, fever, headache, hyperfibrinogenaemia, jittery feeling, lethargy, nausea, vomiting, somnolence, stinging at infusion site, stomach discomfort, tingling, urticaria, vasomotor reactions with rapid infusion.

Food Interaction

Volume of Distribution

The pharmacokinetic profile of the human antihemophilic factor needed to be studied by the two-compartment theory as not all of it stays just in blood plasma. The central and peripheral volume of distribution in adults weight an average of 68 kg were 2.81 L and 1.90 L respectively.

Elimination Route

After intravenous administration of the human antihemophilic factor the values of Cmax, AUC and Tmax were 100 IU/ml, 1450 IU h/ml and 0.43 h respectively. In a second clinical trial, the treatment was administered for six months and the values of Cmax, AUC and Tmax were 99 units/ 100 ml, 1471 units h/ 100ml and 16 h, respectively.

Half Life

The mean half-life of human antihemophilic factor administered in hemophilic A patients is 14.8 hours.

Clearance

The reported clearance for the administration of antihemophilic factor is 0.15 L/h in adults with an average weight of 68 kg. In the same study, there was a separation of the intercompartment clearance which is 0.16 L/h. The clearance rate was reported to be significantly decreased with increasing age and significantly increased in patients that presented a blood type of gourp O.

Elimination Route

Intravenous administration of human antihemophilic factor is rapidly eliminated primarly through the reticuloendothelial system.

Pregnancy & Breastfeeding use

Pregnancy Category C. Either studies in animals have revealed adverse effects on the fetus (teratogenic or embryocidal or other) and there are no controlled studies in women or studies in women and animals are not available. Drugs should be given only if the potential benefit justifies the potential risk to the fetus.

Contraindication

In individuals who have had an anaphylactic or severe systemic reaction to antihemophilic factor or von Willebrand factor preparations.

Storage Condition

Storage Conditions

Store between 2-8° C. Use within 3 hr of reconstitution; do not refrigerate after reconstitution due to risk of precipitation.

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