How the Blood Clotting Process Works

VWD is the most common hereditary bleeding disorder, occurring in about 1% of the population. It is caused by a deficiency or defect in von Willebrand factor (VWF), a protein in the blood that is critical to the clotting process. People who have VWD take longer than normal to stop bleeding. In order to understand VWD and its treatment, it helps to know how blood coagulation works and how Humate-P^® helps clots form properly.

When a blood vessel is injured, a number of events take place to stop any bleeding that might occur. The goal is to form a stable clot to stop the bleeding. Here is a general description of the blood clotting process:

The blood vessel is injured.
The blood vessels constrict, or tighten, to slow the blood flow (vasoconstriction).
Platelets—small cells in the blood—rush to the site of injury and cling to platelet receptors to form bridges.
Together, the platelet bridges and von Willebrand factor (VWF) form layers, which act like a plug to stop the bleeding.
Other clotting factor proteins also rush to the injury site to reinforce the clot.

VWF in normal human blood—and in Humate-P^®1—have a lot of "high molecular weight multimers" (HMWMs). Humate-P^® has the most HMWMs amongst all of the VWF concentrates currently on the market.

The high molecular weight multimers (HMWMs) found in normal VWF have a lot of platelet receptors, so more platelets can gather together to form a plug.

In a study of six factor concentrates, Humate-P had the highest amount of HMWMs¹, making it as close as it gets to normal VWF.

By contrast, low molecular weight multimers (LMWMs) have fewer platelet receptors, so they form a less stable plug, which makes long-term blood clotting difficult or impossible.

Important Safety Information

Humate-P is indicated for treatment and prevention of bleeding in adult patients with hemophilia A (classical hemophilia). Humate-P is also indicated in adult and pediatric patients with von Willebrand disease (VWD) for (1) treatment of spontaneous and trauma-induced bleeding episodes, and (2) prevention of excessive bleeding during and after surgery. This applies to patients with severe VWD, and patients with mild and moderate VWD for whom use of desmopressin is known or suspected to be inadequate. Humate-P is not indicated for the prophylaxis of spontaneous bleeding episodes.

Humate-P is contraindicated in individuals with a history of anaphylactic or severe systemic response to antihemophilic factor or von Willebrand factor preparations.

Monitor for intravascular hemolysis and decreasing hematocrit values in patients with A, B, and AB blood groups who are receiving large or frequent doses. Also monitor VWF:RCo and FVIII levels in VWD patients, especially those undergoing surgery.

Thromboembolic events have been reported in VWD patients receiving coagulation factor replacement. Caution should be exercised and antithrombotic measures considered, particularly in patients with known risk factors for thrombosis.

Humate-P is derived from human plasma. The risk of transmission of infectious agents, including viruses and, theoretically, the Creutzfeldt-Jakob disease (CJD) agent, cannot be completely eliminated.

In patients receiving Humate-P in clinical studies for treatment of VWD, the most commonly reported adverse reactions observed by >5% of subjects are allergic-anaphylactic reactions, including urticaria (hives), chest tightness, rash, pruritus (itching), and edema (swelling). For patients undergoing surgery, the most common adverse reactions are postoperative wound or injection-site bleeding, and epistaxis (nosebleed).

Please see full prescribing information.

You are encouraged to report negative side effects of prescription drugs to the FDA. Visit www.fda.gov/medwatch or call 1-800-FDA-1088.

References

Metzner HJ, Hermentin P, Cuesta-Linker T, Langner S, Müller H-G, Friedbold J. Characterization of factor VIII/von Willebrand factor concentrates using a modified method of von Willebrand factor multimer analysis. Hemophilia. 1998;4(suppl 3):25-32.