Adverse effects of IgG therapy.

IgG is widely used for patients with immune deficiencies and in a broad range of autoimmune and inflammatory disorders. Up to 40% of intravenous infusions of IgG may be associated with adverse effects (AEs), which are mostly uncomfortable or unpleasant but often are not serious. The most common infusion-related AE is headache. More serious reactions, including true anaphylaxis and anaphylactoid reactions, occur less frequently. Most reactions are related to the rate of infusion and can be prevented or treated just by slowing the infusion rate. Medications such as nonsteroidal anti-inflammatory drugs, antihistamines, or corticosteroids also may be helpful in preventing or treating these common AEs. IgA deficiency with the potential of IgG or IgE antibodies against IgA increases the risk of some AEs but should not be viewed as a contraindication if IgG therapy is needed. Potentially serious AEs include renal dysfunction and/or failure, thromboembolic events, and acute hemolysis. These events usually are multifactorial, related to combinations of constituents in the IgG product as well as risk factors for the recipient. Awareness of these factors should allow minimization of the risks and consequences of these AEs. Subcutaneous IgG is absorbed more slowly into the circulation and has a lower incidence of AEs, but awareness and diligence are necessary whenever IgG is administered.