Human anti-D immunoglobulin contains specific antibodies (IgG) against the Rh(D) antigen of human erythrocytes. It can also contain antibodies to other Rh antigens, e.g. anti-Rh C antibodies.
During pregnancy, and especially at the time of childbirth, foetal RBCs may enter the maternal circulation. When the woman is Rh(D) negative and the foetus Rh(D) positive, the woman may become immunised to the Rh(D) antigen and produce anti-Rh(D) antibodies which cross the placenta and may cause haemolytic disease of the new-born.
Passive immunisation with anti-D immunoglobulin prevents Rh(D) immunisation in more than 99% of cases provided that a sufficient dose of anti-D immunoglobulin is administered soon enough after exposure to Rh(D) positive foetal RBCs.
The mechanism by which anti-D immunoglobulin suppresses immunisation to Rh(D) positive red cells is not known. Suppression may be related to the clearance of the red cells from the circulation before they reach immunocompetent sites or, it may be due to more complex mechanisms involving recognition of foreign antigen and antigen presentation by the appropriate cells at the appropriate sites in the presence or absence of antibody.
The bioavailability of human anti-D immunoglobulin for intravenous use is complete and immediate. IgG is quickly distributed between plasma and extravascular fluid.
Human anti-D immunoglobulin for intramuscular administration is slowly absorbed into the recipient’s circulation and reaches a maximum after a delay of 2 to 3 days.
Human anti-D immunoglobulin has a half-life of about 3 to 4 weeks. This half-life may vary individually from patient to patient.
IgG and IgG-complexes are broken down in cells of the reticuloendothelial system.
Due to induction of and interference with antibodies, there are limited preclinical data of relevance for anti-D immunoglobulin.
Repeated dose testing and embryo-foetal toxicity studies have not been conducted and are impracticable to conduct.
The potential for mutagenic effects of immunoglobulins have not been studied.
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