Researchers have created a model for how factor VIII replacement concentrates behave in the body of hemophilia A patients undergoing surgery, which could allow doctors to calculate more accurate and individualized doses for factor replacement treatment.
The study “A Population Pharmacokinetic Model For Perioperative Dosing Of Factor VIII In Hemophilia A Patients,” was published in the journal Haematologica. Although the researchers admit that the model did not take all possible parameters into account, it is an important step towards better postoperative treatment of people with hemophilia and in reducing costs associated with over treatment.
Hemophilia treatment with factor replacement is not an inexpensive affair; when surgery is involved, physicians often maximize doses to prevent complications that can occur from excessive bleeding. A recent study of patients with hemophilia type A indicated that patients often have either too low or too high levels of factor VIII at different times after surgery.
In order to better understand how to dose factor VIII during and after surgery, researchers at the Erasmus University Medical Center in the Netherlands studied the behavior of factor VIII concentrates in patients. They analyzed how the drug was distributed to different tissues; how long it took before it was cleared from the body; and the mechanisms involved in the clearance.
Such computing, known as pharmacokinetics, allows scientists to build models based on observations of how a drug travels throughout the body, and how it is broken down and transported out of the body.
The group consisted of 119 hemophilia A patients who underwent 198 surgeries. All patients were treated for up to two weeks after surgery. Treatment consisted of a dose of 50 IU per kg before the procedure, followed by either repeated or continuous infusions after surgery.
Measurements showed that about 45% of factor VIII concentrations within 24 hours after surgery were too low. After six days of hospitalization, the measurements were 75% too high which confirmed findings from the earlier study.
Researchers found that the speed of removal of the blood clotting factor from the body was affected by age, blood group, and the severity of surgery. All of the characteristics form the basis for the more accurate, individualized after surgery treatment model.