Gammaplex is a brand of intravenous immunoglobulin (IVIG), a therapy made from concentrated antibodies sourced from donated human blood plasma. It is FDA-approved to treat two conditions: primary immunodeficiency and chronic immune thrombocytopenic purpura (ITP). Both conditions involve an immune system that isn’t working properly, though in very different ways.
Primary Immunodeficiency
Primary immunodeficiency (PI) refers to a group of inherited conditions where the body doesn’t produce enough functional antibodies on its own. People with PI get infections more frequently and more severely than the general population, because their immune systems lack the frontline defenders that normally fight off bacteria and viruses. Gammaplex essentially fills in that gap by delivering a broad supply of ready-made antibodies directly into the bloodstream through an IV.
For PI, Gammaplex infusions are given every three to four weeks on an ongoing basis. The dose is tailored to body weight. This regular schedule keeps antibody levels high enough to provide continuous protection against infections. The 5% formulation is approved for adults and children aged two and older, while the 10% version is currently approved for adults only.
Chronic Immune Thrombocytopenic Purpura
Chronic ITP is a condition where the immune system mistakenly attacks the body’s own platelets, the tiny blood cells responsible for clotting. With too few platelets in circulation, people with ITP bruise easily, bleed from the gums, develop small red or purple spots on the skin, and face a higher risk of serious internal bleeding.
Gammaplex works differently in ITP than it does in PI. Rather than replacing missing antibodies, the concentrated immunoglobulin appears to distract the immune system. The flood of donated antibodies occupies the receptors and pathways that would otherwise be clearing platelets from the blood, giving platelet counts a chance to recover. This makes it useful when a quick boost in platelet count is needed.
How Gammaplex Is Given
Gammaplex is administered as an intravenous infusion, typically in a clinic, infusion center, or sometimes at home once a patient is established on therapy. The infusion starts slowly and the rate is gradually increased if tolerated well. For the 10% formulation, the average infusion takes just under two hours, compared to nearly three hours for the 5% version. That time difference is one of the practical advantages of the higher concentration: the same dose fits into a smaller volume of liquid, so it moves through the IV faster.
Gammaplex 5% vs. 10%
The two formulations differ in more than just concentration. Gammaplex 10% uses a different stabilizing ingredient (glycine) than the 5% version (which contains sorbitol). This matters for a specific group of patients: those with hereditary fructose intolerance. Because sorbitol is converted to fructose in the body, the 5% formulation is contraindicated for anyone with that condition, as well as for infants and neonates whose ability to tolerate sorbitol hasn’t been established. The 10% version sidesteps this issue entirely and can be used safely in people with fructose intolerance.
Both formulations should be stored between roughly 36°F and 77°F and kept in the original carton to protect from light. They should never be frozen. When stored properly, the 5% solution has a shelf life of 36 months.
Common Side Effects
Headache is the most frequently reported side effect across both conditions. In clinical trials for PI, 39% of patients experienced headaches during or after infusion. Fever occurred in 15%, nasal congestion in 13%, and fatigue in 12%. Nausea, rash, and reactions at the infusion site each affected roughly 5% to 9% of patients.
Side effects in the ITP trials followed a similar pattern but with some differences in frequency. Headache affected 34% of patients, while vomiting was notably more common at 23%, compared to 7% in the PI group. Nausea and fever each occurred in about 14% of ITP patients. Joint pain and itching were reported less frequently, at around 6%.
Most of these reactions are temporary and tied to the infusion itself. They tend to be most noticeable during or shortly after treatment and often improve as the body adjusts over subsequent infusions. Staying well-hydrated before and during the infusion can help reduce the likelihood and severity of side effects.
Important Safety Considerations
Like all IVIG products, Gammaplex carries a risk of blood clots and kidney problems, particularly in older adults. Patients over 65 or those with pre-existing kidney conditions or risk factors for clotting are typically infused at the slowest practical rate to minimize these risks. Adequate hydration before treatment is especially important for this group.
Because Gammaplex is derived from human plasma, it undergoes multiple steps during manufacturing to reduce the risk of transmitting infections. However, no blood-derived product can completely eliminate that theoretical risk, which is why each batch is carefully screened and processed.