Immune globulin

Immune globulin is a solution of antibodies, pooled from donated blood, which is sometimes given to patients whose own immune systems are either not working or are suppressed as a side effect of treatment for a particular condition. Immune globulin can also be called gamma globulin. In South Africa, some of the brands available include Intragam® and Polygam®.

What is it used for?

A healthy human body produces proteins called antibodies that act to destroy micro-organisms (bacteria and viruses) that invade the body. In patients who suffer with certain conditions, these proteins become depleted, due to either the condition itself or side effects of treatment, and are therefore susceptible to serious infections. Immune globulin is given to these patients to restore their body's immunity. The use of immune globulin in this way is also called passive immunisation.

For example, immune globulin is given to bone marrow transplant recipients to prevent the development of severe bacterial infections while their own immune system is not functioning. Chronic lymphocytic leukemia patients (whose antibody-producing cells are the malignant cells) are given immune globulin to prevent the recurrent infections these patients sometimes suffer. Use of immune globulin in this condition also allows the use of aggressive chemotherapy that will destroy the patient's own cancerous antibody-producing cells.

Immune globulin is also used to treat other conditions, haematological conditions, rare neurological conditions, and auto-immune conditions, in which a patient's own antibodies attack cells. The use of immune globulin appears to cause the body to reduce its own production of antibodies, thereby improving the patient's condition.

Please note that these substances are not usually first-line treatments for conditions, and that all other forms of treatment should be attempted prior to use.

Description

Immune globulin primarily consists of antibody proteins called immunoglobulin G (IgG) or gamma, although the solution may contain small amounts of other antibody types as well as sugars, proteins and salt.

It is produced by collecting donated blood from at least 1 000 people who have been tested to be free of blood-borne conditions like HIV or hepatitis. The antibody proteins are then separated from the whole blood, and the pH (acidity or basiciity of a solution) of the immune globulin solution is adjusted to match the normal pH of blood. The preparation is also treated to remove any contaminants, including infectious bacteria or viruses.

Recommended dosage

The dose of immune globulin used varies according to the specific problem that it is being used for. When used to counteract immunodeficiency, the dose is designed to produce an antibody level that stays at an effective level over a period of time.

When immune globulin is given to bone marrow transplant recipients, it is usually begun at the time of the transplant and continued for 100 days thereafter, with the objective of maintaining the level of IgG in the patient's blood above 400 mg per deciliter (dL). In patients with B-cell chronic lymphocytic leukaemia (cancer of the white blood cells), the target threshold for antibodies in the patient's blood is usually about 600 mg/dL. Although the amount required to maintain these levels varies from patient to patient (because different patients metabolise the drug at different rates), a dose between 10 and 200 mg per kg of body weight, given every 3 to 4 weeks, is usually sufficient.

Immune globulin is usually given through an injection into the vein (intravenously), although an injection under the skin (subcutaneous) or into the skin (intradermal) may be used in some circumstances.
 

Precautions

Some people may experience severe allergic reactions to other antibody preparations. Generally these people should not be given intravenous immune globulin. Patients with a deficiency of the antibody immunoglobulin A (IgA), specifically, should avoid the use of immune globulin. People with a tendency to form blood clots, or those with kidney problems should also avoid the use of this product, especially the elderly. While many pregnant women have been treated with immune globulin for different problems that have occurred during their pregnancy, since the method of action and specific effects on the foetus are not completely understood, pregnant women should avoid the use of immune globlulin, unless it is clearly necessary. Any patient who is given immune globulin should be monitored carefully, and epinephrine (adrenaline medication) should be kept available in case a severe allergic reaction is experienced. Immune globulin which was made to be given through intramuscular injection should never be administered intravenously.

Side effects

Administration of intramuscular immune globulin (injection into the muscle) may result in tenderness, swelling and possibly hives at the site of the injection.

Intravenous immune globulin may cause more severe reactions related to rapid introduction into the blood system. Possible side effects include headache, backache, aching muscles, fever , low blood pressure and chest pain. More commonly, fever accompanied by chills or nausea and vomiting may be experienced. If these side effects occur, they are usually related to the immune globulin being administered too rapidly. If the rate of infusion is reduced, or if the infusion is stopped temporarily, negative effects will generally disappear. Rarely, potentially serious side effects are observed, such as kidney failure and aseptic meningitis.

Interactions

The use of immune globulin may reduce the effectiveness of certain vaccinations for a few months following the use of the preparation; for example measles, mumps and rubella (German measles). Patients who have been given immune globulin should notify their doctors before any vaccinations are given. In addition, in some situations patients may need to have antibody levels measured to determine whether or not they have had previous infection with a specific micro-organism. Use of immune globulin can create the false impression of prior exposure to the organism due to the donated antibodies in their blood.

Should the patient experience vomiting, they may require injections of hydrocortisone.

References
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