Dosing Alternatives in Subcutaneous Immunoglobulin Therapy

Introduction Immunoglobulin G (IgG) replacement therapy is the standard care for patients with primary immune deficiency diseases (PIDDs). Previously, IgG had been administered mostly by intramuscular injection, but since the development of intravenous preparations (IVIg), the IV route has been predominant, especially in the United States. Subcutaneous infusion (SCIg) using small mechanical pumps was introduced in the early 1980s, and has recently become much more popular in the United States with the licensing of a 16% IgG preparation specifically intended for subcutaneous use. Subcutaneous infusion is associated with efficacy comparable to that of IVIg and a higher quality of life among patients. Subcutaneous infusions are usually administered more frequently than IVIg infusions, and since they can be self-administered, SCIg is associated with different requirements for training. For some practitioners and patients unfamiliar with this method of administration, initiating therapy with SCIg or switching from IVIg to SCIg has been a challenge.