The current, most-used treatment for hemophilia B is factor replacement therapy. This is done by infusing (giving the medication into a vein) a FIX product into the affected person. When you infuse FIX concentrate, the FIX is immediately available in the bloodstream, and your body can use it to stop or prevent the bleeding. Some bleeding may be successfully treated with amino caproic acid, often most useful for mouth bleeds, or tranexamic acid, also useful for excessive menstrual bleeding. Both of these medications can be given orally.

When treating on-demand (when you have an active bleed), how much clotting factor you need depends on the following:

You can learn to administer FIX concentrates (to yourself or your child) at home at the first signs of a bleed or for preventive care (which we call prophylaxis, or 鈥prophy鈥). [insert photo of adult infusing self or child peripherally]

Frequency of Infusions for Hemophilia B

How often you or your child need to infuse is based on your bleeding pattern and severity of your hemophilia B. The two types of therapies to consider are prophylaxis (preventive care) and on-demand (also called 鈥渆pisodic鈥 treatment).

Prophylaxis for Hemophilia B

Being on prophylaxis means infusing FIX on a regular schedule to prevent bleeds from occurring. Prophylaxis is recommended for children with severe hemophilia, but it can also be recommended for those who have frequent bleeds. Prophylaxis may also be used in advance of activities that are likely to cause a bleed. There are two types of prophylaxis:

  • Primary 鈥 This type of treatment is usually started in young children at or before the first joint bleed to reduce or prevent joint disease and is continued indefinitely.
  • Secondary 鈥 This type of prophylaxis is started after some joint bleeding has occurred; the patient may even have a target joint. Short-term prophylaxis may be started when a significant bleed has occurred and continues on a regular schedule for a defined period of time, either until the bleed is resolved or for a time after to ensure that the bleed does not occur again. It is also used following surgical procedures.

Possible advantages of prophylaxis include the following:

  • Reduced risk of joint damage
  • Ability to more safely participate in sports and other physical activities
  • Reduced risk of spontaneous bleeding

Possible disadvantages of prophylaxis include the following:

  • Frequent infusions

On-Demand Treatment for Hemophilia B

On-demand (also called 鈥渆pisodic鈥) treatment is used to treat an active bleed. FIX is infused after an injury has occurred or a bleed has started.

Possible advantages of on-demand treatment include the following:

  • Fewer infusions
  • Lower cost

Possible disadvantages of on-demand treatment include the following:

  • Increased risk of joint damage
  • Increased risk of spontaneous bleeds

Infusion Methods for Hemophilia B

All FIX products need to be infused directly into the bloodstream. There are several ways to infuse FIX, and each has its advantages and disadvantages. These include peripheral infusion (accessing a vein with a butterfly needle), port-a-catheter (also called a port), a peripherally inserted central catheter (PICC) line, or a BROVIAC庐 or HICKMAN庐 catheter.

Peripheral Venous Access for Hemophilia B

Peripheral venous access, where a butterfly needle is inserted directly into a vein and is used to infuse FIX into the bloodstream, is commonly used by those who infuse at home but do not have a venous access device, such as a port, PICC line, or BROVIAC庐.Below are some considerations regarding this type of access:

  • Requires a clean technique to be used; sterile technique is not necessary.
  • Low risk of infection when clean technique is used.
  • Treatment is completed fairly quickly if the person鈥檚 veins are large and easy to find.
  • Children鈥檚 veins are often small and difficult to find (and children do not like to sit still for infusions).

Port-a-catheter (Port)

[photo of Child with Port]

A port is a device that is surgically implanted under the skin. It has tubing that is inserted into a central vein. In most cases, it is placed on the chest. Below are some considerations regarding this type of access:

  • The port can be accessed repeatedly for many years.
  • Provides an area where the needle can be placed to infuse factor.
  • The port must be accessed using sterile technique to avoid infection.
  • Children can participate in water activities, as the port is under the skin.
  • Infection: The main risk of a port is the risk of infection.
  • Clotting: A clot may form within the catheter.

Peripherally inserted central catheter (PICC)

A PICC line is a catheter inserted into a large vein in the arm that is then connected to an even larger blood vessel in the chest. Part of the catheter stays outside of the arm, and infusions are done through that device. This device is easy to use and does not require a stick through the skin. A sterile dressing is applied over the site where the PICC comes out of the skin, and that dressing must be kept clean and drive. It is generally changed weekly. However, PICC lines only last a few weeks or months.


BROVIAC庐 catheters and HICKMAN庐 catheters (often referred to as 鈥渂roviacs鈥) are similar to a PICC line. However, A BROVIAC庐 catheter is placed directly into a central vein and threaded to a position just above the heart. It is tunneled under the skin and brought out away from the site where it enters the vein to theoretically prevent bacteria from gaining access to the central portion of the catheter. BROVIAC庐 catheters contain a “cuff” that is under the skin. As the skin grows into this “cuff,” the catheter becomes more stable, reducing the chance of it becoming pulled out. Like the PICC line, his device is easy to use and does not require sticks into the person鈥檚 skin. The difference is that these catheters can last for a prolonged period of time. The most common long-term complications of this type of central line are infection, movement that takes the catheter out of the proper position, and damage to the catheter.

Products for Hemophilia B

In the United States, there are two types of FIX products used to treat hemophilia B today: plasma-derived products and recombinant factor concentrates.

Plasma-Derived Products for Hemophilia B

A plasma-derived product is a factor concentrate made from carefully-screened, donated blood plasma. During the manufacturing process, the proteins extracted from the plasma go through a series of extensive sterilization procedures to eliminate viruses and other contaminants.

Recombinant Factor Concentrates for Hemophilia B

In the early 1980s, the cloning of FVIII and FIX and subsequent expression of functional proteins occurred. This was during the 鈥渂ad blood鈥 era (when many individuals with hemophilia being treated with plasma-derived clotting factor were infected with HIV and/or HCV). This led to the development and commercialization of recombinant clotting factors. These initial products were manufactured using Chinese hamster ovary cells or baby mouse kidney cells. Manufacturers injected these cells with the factor gene so that large amounts of the factor protein could be produced. Since the proteins are extracted from animal cells, they are not at risk for containing human viruses. Some factor concentrate products are stabilized using human albumin, while others are stabilized using sucrose. This was life-changing for many with hemophilia, allowing for prophylactic (or preventive) treatment. Some companies are now using human embryonic kidney (HEK) cells to grow the factor.

Recombinant factor concentrates can be standard or long-acting. While long-acting factor costs more per IU, you may need to infuse less often.

Dosage for Hemophilia B

Your hematologist will determine your FIX dosage, and it鈥檚 based on your weight, the severity of your hemophilia B, and your bleeding pattern. Keeping a log of your bleeding, pain, and infusions is critical in achieving the most effective dosing and treatment. Your dose will likely differ for major, minor, and prophylactic dosing. The dosage will be indicated in units of FIX. In addition, dosage may be adjusted based on how your body uses the FIX product, since some people may have a longer or shorter half-life with certain products.

Half-life is how long it takes the body to use up half of the infused dose of factor. The half-life of FIX products available today is 18 to 24 hours for standard recombinant FIX products and 3 to 5 days for long-acting recombinant FIX products.

Each of us process factor differently, so these times may vary. Your hematologist may adjust your dosage based on your bleeding history and/or factor level testing.

FIX concentrates are measured in international units (IU). One IU is equivalent to the amount of factor activity found in 1 cc or 1 ml of fresh plasma. FIX products are delivered in glass vials with labels indicating the number of IU per vial. Manufacturing companies produce common size vials, but at times, depending on body weight, a person may need to mix more than one vial to achieve the necessary dosage. Exact dosage vials are usually not available. However, multiple vials can be mixed to add up to the approximate number of units needed.

FIX dosages are calculated by the amount of factor units needed to raise one kilogram of weight to normal level activity. Most FIX products indicate that 50 units (.5 IU/Kg) are needed to raise one kilogram of weight to normal range activity.

Inhibitors for Hemophilia B

Some people with hemophilia B develop antibodies to FIX. This is called an inhibitor. Approximately 3% of people with hemophilia B develop inhibitors. The inhibitors attack FIX so that it no longer works. These antibodies are called inhibitors. In such cases, clotting factor called VIIa can be used to complete the clotting process. While inhibitors in people with hemophilia B are less common than hemophilia A, they can be even more challenging as about half of hemophilia B inhibitor patients will develop an anaphylactic reaction to infused FIX, which can be life-threatening.

In addition to the type and severity of hemophilia someone has, there are other risk factors:

  • Age/number of exposures to factor product
  • Family history of an inhibitor
  • Race/ethnicity (people of African American and Hispanic descent are at a higher risk of developing an inhibitor)
  • Gene mutation (there are ongoing studies that indicate the type of genetic mutation one has may indicate a higher risk of inhibitor development)
  • Intensive factor therapy related to surgery or trauma.

What are the symptoms of an inhibitor for Hemophilia B?

Inhibitors destroy the infused FIX, as well as the FIX produced naturally by the body in people with mild and moderate hemophilia. If you are treating a bleeding episode, following your current treatment protocol, and the bleeding is not getting better, or may actually be getting worse, this is a key sign that an inhibitor may have developed. A person who doesn鈥檛 have an inhibitor will heal from injuries or feel better after the FIX is infused, or their treatment plan is completed. Those with hemophilia B who have an inhibitor are at higher risk for an anaphylactic reaction when exposed to FIX.

How are inhibitors detected?

Anyone with hemophilia B should be tested for inhibitors regularly, at least once per year. A blood test called activated partial thromboplastin time (APTT) is performed soon after factor concentrate is infused to calculate the time it takes for the person鈥檚 blood to clot. If clotting time is outside the range expected after an infusion, a second test called a Bethesda assay is performed to confirm the diagnosis and to determine the level of inhibitor that the person has developed. The Bethesda assay determines how many Bethesda Units (BUs) a patient has. Fewer than 5 BUs is considered a low-titer inhibitor, and more than 5 BUs is considered high-titer inhibitor.

Inhibitor testing should be initiated if a patient of any age is responding poorly to treatment. Some HTCs test more frequently in the early days of treatment, and many test before every surgery and at annual comprehensive clinic visits.

If you or your child are diagnosed with an inhibitor, your hematologist will likely want you to not infuse for 48 hours to check your BU assay.

Are all Hemophilia B inhibitors the same?

No. Inhibitors come in different degrees of severity. They are measured in titers (the level of inhibitors present in a person鈥檚 blood, which is measured in BUs).


Here is some terminology associated with inhibitors:

  • Titer: The inhibitor titer is measured in Bethesda Units (BUs). This number represents the level of inhibitors in a person鈥檚 body. Inhibitors are classified as follows:
  • Low Titer: When the inhibitor level in the blood is lower than 5 BU. The number, and therefore strength, of the inhibitor is low. Provided, there is no anaphylactic reaction, people with low-titer inhibitors can sometimes continue to use FIX products to treat bleeds; they just need a lot more of it. Low-titer inhibitors can sometimes resolve on their own.
  • High Titer: When the level of inhibitors found in the blood is greater than 5 BU. The number, and therefore strength of the inhibitor, is high. People with a high titer inhibitor get no benefit from FIX, no matter how much they infuse.
  • Anamnestic Response: Once an inhibitor is present, the strength with which the body reacts to further exposure of factor concentrate, also called immune response or immunologic response, can further classify the inhibitor type.
  • Low Responder: When people with low-responding inhibitors receive FIX, the inhibitor titer does not rise. Because the titer stays low, they may be able to control bleeding by using larger quantities of FIX concentrates.
  • High Responder: When people with high-responding inhibitors are exposed to FIX, the immune system quickly triggers even more inhibitor development.

Personal Stories about Living with An Inhibitor

CDC鈥檚 National Center on Birth Defects and Developmental Disabilities (NCBDDD) hosts a Flickr Album featuring the stories of people with hemophilia who have also experienced the added challenge of an inhibitor. This Flickr Album provides powerful, personal testimonials on what it鈥檚 like to live with hemophilia and an inhibitor. It is aimed at raising awareness of this serious bleeding disorder complication, the need for continued inhibitor research, and the importance of routine inhibitor screening.

For more information about inhibitors

  • Center for Disease Control and Prevention (CDC) website, including results of the CDC’s 6-year, Hemophilia Inhibitor Research Study (HIRS), which tested the feasibility of conducting national monitoring for inhibitors amongst people with hemophilia in the United States.
  • World Federation of Hemophilia Inhibitor Primer
  • Canadian Hemophilia Society Inhibitor Guide
  • Managing Your Child鈥檚 Inhibitor: A Practical Guide for Parents, by Laureen A. Kelley
  • CLINICAL TRIALS 鈥 There may be some current clinical trials in hemophilia with inhibitors. Click here for more information on clinical trials.

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