Intravenous immunoglobulin, commonly called IVIG, is a concentrated solution of antibodies collected from the blood plasma of thousands of healthy donors and delivered directly into a vein. It contains over 90% IgG, the most abundant type of antibody in human blood, and is used both to replace missing antibodies in people with immune deficiencies and to calm an overactive immune system in autoimmune and inflammatory conditions. Each batch is pooled from anywhere between 1,000 and 100,000 donors, giving it an extraordinarily broad range of antibodies that reflect the collective immune experience of the donor population.
How IVIG Is Made
The manufacturing process starts with large pools of donated plasma. These pools are fractionated, a process that separates the plasma into its component proteins and isolates the IgG antibodies. Because the product comes from human blood, manufacturers use multiple steps to eliminate the risk of transmitting viruses. Two of the most important are solvent/detergent treatment, which destroys the outer coating of enveloped viruses, and pasteurization (sustained heating). Each of these steps alone reduces viral contamination by a factor of 100,000 to 1,000,000, and using them together creates a wide safety margin. The final product closely mirrors the antibody composition found in normal human plasma, including small amounts of other immunoglobulin types, cytokines, and soluble receptors.
How It Works in the Body
IVIG does different things depending on why it’s being given. For people who can’t produce enough antibodies on their own, it works as straightforward replacement therapy, supplying the infection-fighting antibodies their bodies lack.
Its role in autoimmune and inflammatory conditions is more complex. When the immune system mistakenly attacks the body’s own tissues, it often does so through autoantibodies that latch onto cells and flag them for destruction. IVIG interferes with this process in several ways. At high doses, the massive influx of IgG essentially floods the docking sites (called Fc receptors) on immune cells, occupying them so autoantibodies can’t trigger an attack. It also turns up the activity of an inhibitory receptor on immune cells that acts like a brake pedal, dialing down the inflammatory response. Beyond receptor effects, IVIG can neutralize inflammatory signaling molecules, block the complement cascade (a chain reaction that damages tissue), and shift the balance of immune cell types toward a less aggressive profile.
Conditions Treated With IVIG
The FDA has approved IVIG for several conditions, including primary immunodeficiency disorders, chronic immune thrombocytopenic purpura (ITP), and chronic inflammatory demyelinating polyneuropathy (CIDP). In practice, it’s also widely used off-label for dozens of other conditions where the immune system is causing harm.
Primary Immunodeficiency
People born with defects in antibody production rely on regular IVIG infusions to maintain a protective level of IgG. Without it, they face repeated, sometimes life-threatening infections. For these patients, IVIG is typically given every three to four weeks as ongoing maintenance therapy.
Immune Thrombocytopenia (ITP)
In ITP, the immune system destroys platelets, the blood cells responsible for clotting. IVIG works here primarily by blocking the receptors on immune cells in the spleen that would otherwise grab and destroy antibody-coated platelets. It also suppresses autoantibody production and inhibits complement-mediated platelet destruction. The response is fast: in a recent clinical trial, about 89% of patients reached a healthy platelet count within seven days, with a median response time of just three days. Roughly 72% of patients achieved a strong response within that first week. IVIG’s effects in ITP can begin within 24 to 48 hours of infusion, making it especially useful when platelet counts are dangerously low and bleeding risk is high.
Guillain-Barré Syndrome
Guillain-Barré syndrome (GBS) is an acute condition in which the immune system attacks the nerves, causing progressive weakness that can lead to paralysis. IVIG is one of two standard treatments (the other being plasma exchange). The standard course is five consecutive days of infusion. Despite treatment, about 20% of severely affected patients still can’t walk independently after six months. Between 8% and 16% of treated patients experience a temporary setback after initially improving, though a second course of IVIG usually helps them recover again.
CIDP
CIDP is essentially the chronic cousin of Guillain-Barré. It causes progressive weakness and impaired sensation in the legs and arms over a period of months. IVIG is a first-line treatment and is given in repeated cycles to prevent relapses and maintain nerve function.
What the Infusion Is Like
IVIG is given through an IV line, typically in a hospital outpatient center or infusion clinic. About 30 minutes before the infusion starts, most patients receive premedication to reduce the chance of a reaction. This usually includes acetaminophen and an antihistamine. Patients with a history of reactions or those considered high-risk may also receive a steroid through their IV line. Adequate hydration before the infusion is important, and patients at risk of kidney problems may receive an IV fluid bolus beforehand.
The infusion itself starts slowly, typically at about 0.5 mL per kilogram of body weight per hour. The rate is gradually doubled every 15 to 30 minutes as long as the patient tolerates it well. For someone who has tolerated previous infusions without trouble, the maximum rate can reach 4 to 8 mL/kg/hour. For older patients, those with kidney impairment, or heart transplant recipients, the rate is kept lower. Depending on the dose and how quickly the rate can be increased, a single infusion session can take anywhere from a few hours to most of the day. Multi-day courses, like the five-day protocol used for Guillain-Barré, mean spending significant time in the infusion chair.
Side Effects and Risks
Most side effects are mild and temporary. Headache is the most common, affecting more than half of patients. Flushing, fever, chills, fatigue, and general malaise are also frequent. These reactions often improve simply by slowing the infusion rate or taking over-the-counter pain relievers.
Serious adverse effects are rare but worth knowing about. Aseptic meningitis, an inflammation of the membranes surrounding the brain that is not caused by infection, occurs in roughly 0.6% to 1% of patients. It causes severe headache, neck stiffness, and sensitivity to light, usually within 24 to 48 hours of the infusion, and resolves on its own. Kidney impairment is another uncommon but potentially dangerous complication, particularly in patients who are already dehydrated or have pre-existing kidney disease. Thrombosis (blood clots), hemolytic anemia (destruction of red blood cells), and transfusion-related acute lung injury are among the rarest serious risks.
Cost and Availability
IVIG is one of the more expensive therapies in medicine. Pricing has climbed steadily over the years. In the early 2000s, the average U.S. price was around $30 per gram. By 2010, liquid formulations had reached roughly $70 per gram, and Medicare reimbursement settled around $73 per gram. For a 70-kilogram adult receiving 2 grams per kilogram for an autoimmune condition, that translates to 140 grams per course, putting the drug cost alone in the range of $10,000 per treatment cycle before hospital and administration fees.
Supply shortages have been a recurring issue. Because IVIG depends entirely on voluntary plasma donations, production can’t simply be scaled up on demand. Industry consolidation, shifts in manufacturing processes, and growing demand for the product have all contributed to periodic allocation restrictions. These shortages can force hospitals to prioritize which patients receive IVIG and delay treatment for others.