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Byline: Tove Tuntland, Aleksandrs Odinecs, Conrad M. Pereira, Connie Nosbisch, Jashvant D. Unadkat Keywords: Pregnancy; placenta; maternal-fetal exchange; in vitro-in vivo correlation; dideoxynucleoside drugs; human immunodeficiency virus Abstract: Objective: We tested the hypothesis that the mechanism, rate, and extent of in vivo placental transfer of dideoxynucleoside drugs against human immunodeficiency virus can be predicted by the in vitro perfused human placenta and the drug octanol-water partition coefficient. Study Design: Near-term pregnant macaques (Macaca nemestrina) underwent long-term catheterization for the administration of 4 dideoxynucleosides against human immunodeficiency virus: zidovudine, didanosine, zalcitabine, and stavudine. Maternal plasma, fetal plasma, and amniotic fluid concentrations were determined frequently after intravenous bolus and/or infusion of the drugs administered into the maternal or fetal circulation on separate occasions. Antipyrine was included in all experiments as a marker of placental blood flow. The mechanism, rate, and extent of placental transfer of the 4 dideoxynucleosides in perfused human placenta were determined and compared with the findings obtained by others. Results: The mechanism and rate of the antipyrine-normalized placental transfer of the 4 dideoxynucleosides in perfused human placenta were highly correlated with those observed in vivo. The extent of placental transfer (fetal/maternal steady-state plasma concentration ratio) was also highly correlated with both the antipyrine-normalized placental transfer clearance (clearance index) determined in the in vitro perfused human placenta model (r.sup.2 = 0.95, in vitro clearance-index model) and the drug octanol-water partition coefficient (r.sup.2 = 0.99, in vitro partition-coefficient model). To determine the predictive capacity of these correlative models, we predicted the fetal/maternal steady-state plasma concentration ratio of each drug after excluding the data on that drug from the model fit. Both in vitro models to predict in vivo placental transfer of drug models resulted in good predictions of the observed fetal/maternal steady-state plasma concentration ratio (mean error: in vitro clearance-index model = -1.2%; in vitro partition-coefficient model = 3.9%). Conclusions: We propose that our models will accurately predict the extent of placental transfer of dideoxynucleoside drugs against human immunodeficiency virus. The models may also be applicable to other classes of drugs, regardless of therapeutic category, provided that these drugs passively diffuse across the placenta. Such a result will expedite phase 1 clinical trials of drugs in pregnant women. (Am J Obstet Gynecol 1999;180:198-206.) Author Affiliation: Seattle, Washington From the Department of Pharmaceutics, School of Pharmacy,.sup.a and the Regional Primate Research Center,.sup.b University of Washington Article History: Received 1 December 1997; Revised 29 June 1998; Accepted 14 July 1998 Article Note: (footnote) [star] Supported by grants HD27438, HD02274, and RR00166 from the National Institutes of Health., [star][star] Reprint requests: Jashvant D. Unadkat, PhD, Professor, Department of Pharmaceutics, Box 357610, School of Pharmacy, University of Washington, Seattle, WA 98195-7610., a 0002-9378/99 $8.00 + 0 6/1/93227

Updates By Carol A. Kemper, MD, FACP, Clinical Associate Professor of Medicine, Stanford University, Division of Infectious Diseases; Santa Clara Valley Medical Center, Section Editor, Updates; Section Editor, HIV, is [...]

Source: Ross L, et al. AIDS Res Hum Antiretrovir. 2001;17:1107-1115. STUDIES SUGGEST THAT THE AD-ministration of stavudine (D4T), independent of zidovudine (AZT), may induce HIV genotypic mutations commonly associated with [...]