ITP Treatments

Anti-D Antibody

Anti-D antibody is a blood product used to achieve a temporary and occasionally long-term elevation of the platelet counts. It is marketed under several trade names including WinRho SDF and Rhophylac. According to one study, it has 79-90% efficacy, depending on the type of ITP.

It is a sterile freeze dried gamma globulin fraction containing antibodies to Rh (D). Within a few minutes of an intravenous infusion, anti-D coats the recipient’s (normal) red cells with purified IgG, which resembles the coating of platelets by the (abnormal autoimmune) ITP immunoglobulin. After D(Rh)-positive red cells are coated with anti-D, they compete with the recipient’s IgG(ITP)-coated platelets for phagocytosis (destruction) by macrophages in the spleen. Usually, IgG(WinRho)-coated red cells succeed in blocking the spleen’s destruction of IgG (ITP)-coated platelets, thus increasing platelet counts. Significant increases in platelet counts occur within 1-3 days with peak counts observed 8 days after infusion. The effects last approximately one month.

Anti-D is made from human plasma derived from a limited list of donors in a special program. It undergoes a viral inactivation and micro filtration process using solvent/detergent. Donors are stimulated to produce Ig with especially high levels of specific antibodies so a smaller amount of the product is required. This reduces the cost per infusion by about half of what IVIg would cost. Also, because anti-D has been treated to inactivate any viral contamination, it is safer to use than IVIg. However, because anti-D antibodies and action are so specific, it is only effective for people who are Rh positive (85% of population) and have a spleen. It may not be suitable for some pregnant women.

Dosage

Suggested dosing is 50 mcg/kg of bodyweight although some clinical studies report greater success at a 75 mcg/kg dose. The infusions take about three to five minutes for the IV push and about 30 minutes for the IV drip. Anti-D can be given as a single dose or as two divided doses given on separate days. The dose and frequency of administration are determined from the patient's clinical response.

Side Effects

Side effects developed following 4% of the infusions, and included headaches, chills, fever and body aches. Pain and swelling at the injection site have occurred in a few cases. A remote risk of anaphylaxis (shock response) exists for patients with hypersensitivity to blood products. Because of the specific antibodies that the product uses, anemia caused by hemolysis (destruction of red blood cells) can also be a problem. RBC levels should be monitored, especially in people with low hemoglobin.

News

Continued postmarketing safety surveillance has shown rare, but severe and sometimes fatal, intravascular hemolysis and potentially serious complications, including disseminated intravascular coagulation in patients with ITP. Physicians should discuss the risks and benefits of WinRho SDF, alert patients who are being treated for ITP about the signs and symptoms associated with intravascular hemolysis (back pain, shaking chills, fever, discolored urine, decreased urine output, sudden weight gain, fluid retention/edema, and/or shortness of breath) and advise patients to report any symptoms immediately to their physicians.
Maltose in IVIG products, such as the liquid formulation of WinRho SDF, has been shown to give falsely high blood glucose levels in certain types of blood glucose testing systems. Due to the potential for falsely elevated glucose readings, only testing systems that are glucose-specific should be used to test or monitor blood glucose levels in patients receiving this product.
From www.medwatch.gov

Help

1-800-4WINRHO (1-800-494-6746)
winrho@baxter.com

Baxter Healthcare Corporation
One Baxter Parkway
Deerfield, IL 60015