title: Pharmacokinetics of 250 μg anti-D IgG in the third trimester of pregnancy: an observational study.
abstract: OBJECTIVE
  We present a pharmacokinetic study evaluating a single intramuscular dose of 250 μg anti-D immunoglobulin in the third trimester of pregnancy. The aim of the study was to determine the kinetic profile and duration of detectable levels of anti-D.
  
  
  METHODS
  Prospective observational study.
  
  
  METHODS
  Antenatal outpatient clinic.
  
  
  METHODS
  Healthy Rhesus D (RhD)-negative pregnant women with an RHD-positive fetus.
  
  
  METHODS
  Serial plasma anti-D quantitations following antenatal administration of anti-D immunoglobulin were performed using flow cytometry. Kinetic profiles for anti-D levels were generated from the concentration values at predetermined sampling time points. The half-lives were calculated by linear regression analysis. Main outcome measures. Time vs. concentration profile, half-life and anti-D concentration ≥1 ng/mL close to term.
  
  
  RESULTS
  The maximal plasma concentration of anti-D was usually seen at 3-10 days postinjection, with a median value of 25 ng/mL. The half-life varied between individuals, with a median of 23 days. We found detectable levels of anti-D IgG within two weeks of parturition in 11 of 12 women.
  
  
  CONCLUSIONS
  The preparation of anti-D immunoglobulin used in the present study, if administrated in pregnancy week 28-30, is associated with detectable levels of anti-D in most women at the time of delivery. Although the half-time is 23 days, it is uncertain whether all mothers have adequate anti-D concentrations at term. Alternative strategies may be evaluated in the future, with repeated administration of antenatal prophylaxis at term rather than conventional postpartum administration of anti-D.
authors.affiliation: Department of Obstetrics and Gynecology, Karolinska University Hospital and Karolinska Institute, Stockholm, Sweden. eleonor.tiblad@karolinska.se
authors.forename: Eleonor
authors.initials: E
authors.lastname: Tiblad
authors.forename: Agneta
authors.initials: A
authors.lastname: Wikman
authors.forename: Anders
authors.initials: A
authors.lastname: Rane
authors.forename: Yvonne
authors.initials: Y
authors.lastname: Jansson
authors.forename: Magnus
authors.initials: M
authors.lastname: Westgren
mesh_terms: D000328:Adult; D005260:Female; D006207:Half-Life; D006801:Humans; D007273:Injections, Intramuscular; D007518:Isoantibodies / Q000097:blood*; D010599:Pharmacokinetics; D011247:Pregnancy; D011263:Pregnancy Trimester, Third / Q000097:blood*; D011446:Prospective Studies; D012203:Rh Isoimmunization / Q000097:blood / Q000517:prevention & control; D018029:Rho(D) Immune Globulin / Q000008:administration & dosage / Q000097:blood*; D055815:Young Adult
chemical_list: D007518:Isoantibodies; D018029:Rho(D) Immune Globulin