RE: Multiple amniotic fluid samples

Dear Dr. Hutson, The general methodological approach with amniotic fluid PK modeling is to pool the fluid from all the sacs at a given time point and measure the concentration in that pooled fluid. The concentrations in the amniotic fluid are generally modeled as a single compartment with other compartments representing the fetus, the placenta, and maternal plasma. There is some elegant work from Dr. Boudinot's group in this area (see below). If you have measured amniotic concentrations from different sacs at each time point then that variability can be simply assigned to noise (sigma) as indicated by Dr. Gibiansky. For my Ph.D. work we were interested mainly in fetal PD and maternal/fetal PK are summarized in the JPET paper indicated below. Fetal PK can be easily modeled by simultaneously analyzing maternal plasma, fetal plasma, and overall fetal tissue concentrations (Both fetal amount and fetal plasma concentrations are needed to estimate the fetal volume of distribution) Huang CS-H, Boudinot FD and Feldman S. Maternal-fetal pharmacokinetics of zidovudine in rats. Journal of Pharmaceutical Science 1996; 85: 965-970. Samtani MN, Pyszczynski NA, Dubois DC, Almon RR, Jusko WJ. Modeling glucocorticoid-mediated fetal lung maturation: I. Temporal patterns of corticosteroids in rat pregnancy. JPET. 2006 ;317:117-26. Warm regards...MNS