What Are Inhibitors?

What Are Inhibitors?

Inhibitors, A to B.

Inhibitors might seem mysterious. But understanding them better can help you understand your condition. And get on with life.

What's an inhibitor, anyway?2,3


  • People with hemophilia A or B can develop inhibitors, which prevent their factor VIII or IX treatment from working to form a clot to stop bleeding.

    People with hemophilia A or B can develop inhibitors, which prevent their factor VIII or IX treatment from working to form a clot to stop bleeding.
  • People with hemophilia lack certain clotting factor proteins necessary to control bleeds.

    Their treatment contains factor that replaces missing proteins and helps their blood clot.

    People with hemophilia lack certain clotting factor proteins necessary to control bleeds. Their treatment contains factor that replaces missing proteins and helps their blood clot.
  • But for some people, the factor may suddenly stop working—and antibodies are to blame.

    Antibodies are a part of your body's natural defense system, attacking foreign substances that enter the body. They're valuable for fending off viruses and bacteria.

    Antibodies are a part of your body’s natural defense system, attacking foreign substances that enter the body. They’re valuable for fending off viruses and bacteria.
  • For some people with hemophilia, these antibodies view the factor treatment as foreign and attack it, stopping it from working. The antibodies are called inhibitors.

    For some people with hemophilia, these antibodies view the factor treatment as foreign and attack it, stopping it from working. Those antibodies are called inhibitors.

  • People with hemophilia A or B can develop inhibitors, which prevent their factor VIII or IX treatment from working to form a clot to stop bleeding.

    People with hemophilia A or B can develop inhibitors, which prevent their factor VIII or IX treatment from working to form a clot to stop bleeding.
  • People with hemophilia lack certain clotting factor proteins necessary to control bleeds.

    Their treatment contains factor that replaces missing proteins and helps their blood clot.

    People with hemophilia lack certain clotting factor proteins necessary to control bleeds. Their treatment contains factor that replaces missing proteins and helps their blood clot.
  • But for some people, the factor may suddenly stop working—and antibodies are to blame.

    Antibodies are a part of your body's natural defense system, attacking foreign substances that enter the body. They're valuable for fending off viruses and bacteria.

    Antibodies are a part of your body’s natural defense system, attacking foreign substances that enter the body. They’re valuable for fending off viruses and bacteria.
  • For some people with hemophilia, these antibodies view the factor treatment as foreign and attack it, stopping it from working. The antibodies are called inhibitors.

    For some people with hemophilia, these antibodies view the factor treatment as foreign and attack it, stopping it from working. Those antibodies are called inhibitors.

Inhibitors can happen.

Inhibitors usually appear in young children. But they can develop at any age.4 Some people with hemophilia may be more at risk for getting inhibitors than others.

Severe hemophilia A
up to 3 out of every 10 people5

Hemophilia B
up to 1 out of every 20 people5

Who's most at risk for developing inhibitors?6

  • People with severe hemophilia
  • Children (inhibitors usually develop during childhood)
  • People with a family history of inhibitors
  • African-Americans and Hispanics (higher frequency of inhibitors)7

Some people with hemophilia A or B may develop inhibitors in response to a treatment that contains factor VIII or factor IX. Most inhibitors appear within the first 150 days of exposure to factor VIII.2,8

We don't know why some people get inhibitors and others don't, but scientists are trying to find out.

Complications: 5 things to know

1

Severe hemophilia patients with inhibitors don't bleed more often than other severe hemophilia patients. But their bleeds are more difficult to manage because they don't always respond to standard treatment.9

2

Inhibitor patients may develop serious complications, like uncontrollable bleeding, joint disease, and disabilities.4,10

3

Moderate and mild hemophilia patients may experience a change in bleeding pattern. They're also at risk for serious complications; many experience severe spontaneous bleeding in joints and muscles.11

4

Patients with inhibitors are at increased risk for life-threatening bleeding and are hospitalized more frequently.12

5

Surgeons may be reluctant to perform joint procedures and other operations meant to help improve an inhibitor patient's joint condition and mobility if they're concerned about uncontrollable bleeding.13

FEIBA. Made to help manage inhibitors.

Inhibitors aren't easy to understand. But they may be manageable.

Want to learn more? Check out our About FEIBA page.

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FEIBA [Anti-Inhibitor Coagulant Complex]
Indications and Detailed Important Risk Information for Patients

Indications for FEIBA

FEIBA is an Anti-Inhibitor Coagulant Complex approved for use in hemophilia A and B patients with inhibitors for:

  • Control and prevention of bleeding episodes
  • Use around the time of surgery
  • Routine prophylaxis to prevent or reduce the frequency of bleeding episodes.

FEIBA is NOT for use in the treatment of bleeding episodes resulting from coagulation factor deficiencies without inhibitors to factor VIII or factor IX.

Detailed Important Risk Information for FEIBA

WARNING: EVENTS INVOLVING CLOTS THAT BLOCK BLOOD VESSELS

  • Blood clots that block blood vessels and their effects have been reported during post-marketing surveillance following infusion of FEIBA, particularly following administration of high doses (above 200 units per kg per day) and/or in patients at risk for forming blood clots.
  • If you experience any of these side effects, call your doctor right away.

Who should not use FEIBA?

You should not use FEIBA if:

  • You had a previous severe allergic reaction to the product
  • You have Disseminated Intravascular Coagulation (DIC), or signs of small blood vessel clots throughout the body
  • You have sudden blood vessel clots or blocked blood vessels, (such as, heart attack or stroke)

What other important information should I know about FEIBA?

Events involving blood clots blocking blood vessels (such as blood clot in vein, blood clot in the lung, heart attack, and stroke) can occur with FEIBA, particularly after receiving high doses (above 200 units per kg per day) and/or in patients with risk factors for clotting.

Events of thrombotic microangiopathy (TMA), a condition where blood clots and damage occur in small blood vessels, were reported in an emicizumab (Hemlibra®) clinical trial where patients received FEIBA with emicizumab as part of a treatment plan for breakthrough bleeding. The safety and efficacy of FEIBA for breakthrough bleeding in patients receiving emicizumab has not been established. If you take, or anticipate taking, FEIBA with emicizumab, tell your doctor, since they will need to closely monitor you.

At first sign or symptom of a sudden blood vessel clot or blocked blood vessel (such as chest pain or pressure, shortness of breath, fever, altered consciousness, vision, or speech, limb or abdomen swelling and/or pain), stop FEIBA administration right away and seek immediate emergency medical treatment.

Infusion of FEIBA should not exceed a single dose of 100 units per kg body weight and daily doses of 200 units per kg of body weight. Maximum injection or infusion rate must not exceed 2 units per kg of body weight per minute.

Allergic reactions, including severe, sometimes fatal allergic reactions that can involve the whole body, can occur following the infusion of FEIBA. Stop using FEIBA promptly and call your doctor or get emergency treatment right away if you get a rash, hives or welts, experience itching, tightness of the throat, vomiting, abdominal pain, chest pain or tightness, difficulty breathing, lightheadedness, dizziness, nausea or fainting.

Because FEIBA is made from human plasma it may carry a risk of transmitting infectious agents, such as viruses, variant Creutzfeldt-Jakob disease (vCJD) and, theoretically, the Creutzfeldt-Jakob disease (CJD).

What are the possible side effects of FEIBA?

The most common side effects observed during the prophylaxis clinical study were low number of red blood cells, diarrhea, bleeding into a joint, positive test for hepatitis B surface antibodies, nausea, and vomiting.

The serious side effects seen with FEIBA are allergic reactions and clotting events involving blockage of blood vessels, which include stroke, blockage of the main blood vessel to the lung, and deep vein blood clots.

Call your doctor right away about any side effects that bother you during or after you stop taking FEIBA.

What other medications might interact with FEIBA?

Talk with your doctor about the possibility of formation of blood clots when taking drugs that may prevent clot breakdown such as tranexamic acid, and aminocaproic acid. There have not been adequate studies of the use of FEIBA and rFVIIa (NovoSeven®), or emicizumab together, or one after the other. Use of drugs that may prevent clot breakdown within approximately 6 to 12 hours after the administration of FEIBA is not recommended.

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

Please see FEIBA full Prescribing Information, including BOXED WARNING on blood clots, and discuss with your doctor.