Ex vivo human placental transfer and the vasoactive properties of hydralazine.

OBJECTIVE: The purpose of this study was to determine the placental transfer and fetal vascular effects of hydralazine in an ex vivo human placental system. STUDY DESIGN: Nine placentas from uncomplicated term vaginal or cesarean deliveries were studied by means of the ex vivo single-cotyledon perfusion system. Antipyrine was used for the reference compound in the determination of the clearance index of hydralazine. Fetal vascular effects of hydralazine were determined by the effects on the perfusion pressure of the fetal artery in a constant-flow open system. Variations in fetal pressure were analyzed with the 1-sample Student t test. RESULTS: The clearance index of hydralazine ranged from 0.61 +/- 0. 18 to 0.73 +/- 0.14. The accumulation of hydralazine in the recirculated fetal compartment was linear in relationship to the maternal concentration. Fetal pressure changes were noted in 6 of the 9 placentas, or 66.6%. The mean change in pressure was -4.1 +/- 4.4 mm Hg (P =.0231). CONCLUSIONS: Hydralazine readily crosses the ex vivo human placental perfusion system.

Ex vivo human placental transfer of trovafloxacin.

OBJECTIVE: The purpose of this study was to determine the ex vivo human placental transfer of trovafloxacin from the maternal circulation to the fetal circulation. METHODS: Six placentas from uncomplicated, term, vaginal or cesarean deliveries were studied using the ex vivo isolated cotyledon perfusion chamber; 14C-antipyrine was used as a reference compound to determine the clearance index (CI) of trovafloxacin. RESULTS: The CI of trovafloxacin was 0.19 +/- 0.13 at a mean trough concentration of 1.38 +/- 0.22 microg/ml and 0.16 +/- 0.10 at a mean peak concentration of 7.48 +/- 2.3 microg/ml as determined by our newly developed high-pressure liquid chromatographic assay. Tissue concentration did not exceed maternal concentration, and there was little or no accumulation when the perfusion system was closed for 1 hr. CONCLUSIONS: Trovafloxacin crosses the placenta by simple diffusion and does not accumulate in the media to any extent, nor does it bind to tissue or accumulate in the placenta.

Placental transfer of ritonavir with zidovudine in the ex vivo placental perfusion model.

OBJECTIVE: The object was to determine the placental transfer of ritonavir alone and in combination with zidovudine. STUDY DESIGN: Twelve placental perfusion studies were performed at trough (1-2 microg/mL) and peak (approximately 20 microg/mL) combinations of ritonavir and zidovudine. Accumulation of ritonavir was determined. RESULTS: Transfer of ritonavir at trough concentrations was undetectable (<0.025 microg/mL). The clearance index of ritonavir at peak concentration was 0.085 +/- 0.05 and was unaffected by zidovudine. The fetal concentration of ritonavir was 0.0758 +/- 0.22 microg/mL at a maternal concentration of approximately 20 microg/mL and 25.5 +/- 6.9 microg/mL at a concentration of 100 microg/mL. There was no tissue accumulation of ritonavir either alone or with zidovudine. CONCLUSION: The clearance index of ritonavir at therapeutic levels was extremely low, with little accumulation in the fetal compartment and no accumulation in placental tissue. Zidovudine does not significantly affect the transfer or accumulation of ritonavir.

The ex vivo human placental transfer of the anti-HIV nucleoside inhibitor abacavir and the protease inhibitor amprenavir.

OBJECTIVE: The transfer of abacavir, a new nucleoside inhibitor, and amprenavir, a new protease inhibitor, used for the treatment of human immunodeficiency virus, has been studied in the ex vivo human placental model. METHODS: The ex vivo human placental model used C14 antipyrine to determine the transport fraction and clearance index of these compounds at both the peak and trough serum concentrations. The clearance index accumulation and tissue concentrations were determined for each drug by high pressure liquid chromatography. RESULTS: The clearance index of abacavir was 0.47 +/- 0.19 and 0.50 +/- 0.07 at peak and trough concentrations, respectively. The clearance index of amprenavir was 0.38 +/- 0.09 and 0.14 +/- 0.08 at peak and trough concentrations, respectively. There was no unusual accumulation of either drug in the media or tissue when the perfusion system was closed. CONCLUSION: Abacavir is the first nucleoside compound studied in the perfusion system with a high clearance index. The transfer of the protease inhibitor amprenavir had a clearance index 2.75 times greater than the clearance index of ritonavir at peak concentration determined in a previous study. At trough concentration the clearance index was much less than at the peak concentration. A similar result was found with ritonavir.

The maternal-fetal transfer of lamivudine in the ex vivo human placenta.

OBJECTIVE: Our purpose was to measure the transfer of lamivudine ([-]-2'-deoxy-3'-thiacytidine) across the human placenta both alone and in the presence of zidovudine. STUDY DESIGN: Nine placentas from term, elective cesarean deliveries were analyzed with use of the ex vivo single cotyledon perfusion system. Antipyrine was used as the reference compound to measure the clearance index values of lamivudine alone and in combination with zidovudine. Lamivudine concentrations in the perfusates and tissues were quantified by high-pressure liquid chromatography. RESULTS: The clearance index of lamivudine at a maternal concentration of 1.39 micrograms/ml was 0.23 +/- 0.14. At a peak concentration of 14.68 micrograms/ml the clearance index was 0.14 +/- 0.06. These index values did not significantly change in the presence of 1 or 10 micrograms/ml of zidovudine. In a closed recirculating system the fetal lamivudine concentration increased as more lamivudine was added to the maternal perfusate. The addition of zidovudine did not influence this transfer. CONCLUSION: Lamivudine appears to cross the placenta by simple diffusion and its transfer does not appear to be altered by zidovudine.

Ex vivo human placental transfer of anti-human immunodeficiency virus compounds.

OBJECTIVE: The transfer of anti-human immunodeficiency virus (HIV) drugs has been studied in the ex vivo human placental model. There is a paucity of information on the placental transfer of these drugs because of ethical considerations and the expense involved in the use of the non-human primate model. METHODS: The standardized ex vivo human placental model was used in these studies and the clearance index in relationship to antipyrine was used to determine the role of transfer of non-nucleosides, nucleosides, and a protease inhibitor. Several of the nucleosides and ritonavir were combined with zidovudine (AZT) to determine the effect of the combinations. RESULTS: All non-nucleosides, nucleosides, and the protease inhibitor were found to cross the human placenta by simple diffusion, although at variable rates. Ritonavir did not diffuse as rapidly as the nucleosides, but some diffusion was noted at peak concentrations. CONCLUSIONS: Ex vivo perfusion studies agree with those determined in the non-human primate model and with data from existing clinical trials.

Ampicillin for neonatal group B streptococcal prophylaxis: how rapidly can bactericidal concentrations be achieved?

OBJECTIVE: Our purpose was to determine how rapidly bactericidal concentrations of ampicillin against group B streptococci are achieved in amniotic fluid and cord blood after a 2 gm maternal infusion. STUDY DESIGN: Ampicillin was administered at varying time intervals between 3 and 67 minutes before elective cesarean delivery in 40 women. Samples of amniotic fluid were obtained by amniocentesis just before the uterine incision was made. Umbilical and maternal blood were obtained at the time of delivery. Ampicillin concentrations were measured by high-pressure liquid chromatography. RESULTS: The mean concentrations of ampicillin measured in maternal and umbilical cord sera all exceeded the minimum bactericidal concentrations reported for group B streptococci (0.25 to 2.0 micrograms/ml) and were achieved as soon as 5 minutes after ampicillin infusion. Similarly, bactericidal levels of ampicillin in the amniotic fluid could be detected as early as 5 minutes. However, such concentrations of ampicillin in the amniotic fluid were achieved in only 85% of the pregnancies studied. CONCLUSIONS: Bactericidal levels of ampicillin against group B streptococci can usually be achieved rapidly in both fetal blood and amniotic fluid after a standard 2 gm intravenous dose given to the mother for neonatal prophylaxis.

Ex vivo human placental transfer of rifampin and rifabutin.

OBJECTIVE: The purpose of this study was to determine the ex vivo human placental transfer of rifampin and rifabutin. METHODS: Seven placentas from uncomplicated term vaginal or cesarean deliveries were studied utilizing the ex vivo single cotyledon perfusion system. Antipyrine was used for the reference compound in the determination of the clearance indices of rifampin and rifabutin. RESULTS: The clearance indices of rifampin at maternal concentrations of 1.0 and 10.0 mug/ml were 0.12 +/- 0.05 and 0.12 +/- 0.11, respectively. The clearance indices of rifabutin at maternal concentrations of 1.0 and 10.0 mug/ml were 0.44 +/- 0.11 and 0.37 +/- 0.15, respectively. CONCLUSIONS: Because of its greater lipophilicity, rifabutin was found to have a greater clearance than rifampin. However, because of rifabutin's trend toward greater deposition in tissue, there was proportionately less accumulation of rifabutin in the fetal circulation when compared to rifampin.

Markers of acute and chronic asphyxia in infants with meconium-stained amniotic fluid.

OBJECTIVE: Cord blood pH, lactate, hypoxanthine, and erythropoietin levels have all been used as markers of either acute or chronic asphyxia. We sought to determine whether these index values were significantly different in infants with or without meconium-stained amniotic fluid. STUDY DESIGN: Fifty-six pregnant women in spontaneous labor at term were divided into two groups on the basis of the presence or absence of meconium-stained amniotic fluid. All meconium-stained fluid was centrifuged, and the volume percentage of particulate matter (i.e., meconium) was recorded. Umbilical artery blood and mixed arterial and venous cord blood were obtained at each delivery. Lactate, hypoxanthine, and erythropoietin levels were measured. Statistical analysis included Student t test and rank sum statistics where appropriate. Normal and Spearman correlation coefficients were also used. RESULTS: There were no significant differences in mean umbilical artery pH (7.26 +/- 0.06 vs 7.25 +/- 0.10), lactate levels (32.8 +/- 10 mg/dl vs 30.4 +/- 14.2 mg/dl), and hypoxanthine levels (13.4 +/- 6.7 mumol/L vs 14.0 +/- 6.0 mumol/L) in newborns with meconium (n = 28) compared with controls (n = 28). Erythropoietin levels were significantly greater in newborns with meconium (median 39.5 mIU/ml vs 26.8 mIU/ml, p = 0.039). There was no correlation between the amount of particulate matter and any marker of asphyxia. CONCLUSIONS: There was no correlation between markers of acute asphyxia (i.e., umbilical artery blood pH, lactate, or hypoxanthine) and meconium. However, erythropoietin levels were significantly elevated in newborns with meconium-stained amniotic fluid. This latter marker may better correlate with chronic asphyxia.

Ex vivo human placental transfer of human immunodeficiency virus-1 p24 antigen.

OBJECTIVE: Our purpose was to determine whether human immunodeficiency virus-1 p24 antigen crosses the human placenta and, if so, to determine its clearance index relative to antipyrine. STUDY DESIGN: Eight term human placentas from uncomplicated vaginal or cesarean section deliveries were studied by ex vivo placental perfusion to determine the incidence and concentration required to obtain passage of p24 antigen into the fetal circulation. The concentration of p24 antigen was determined by antigen-capture enzyme immunoassay. RESULTS: The passage of p24 antigen into the fetal circulation was observed in three of five placentas studied when the p24 antigen concentration in the maternal circulation was 2942.8 +/- 401 pg/ml. When the p24 concentration in the maternal circulation was raised approximately fourfold to 14506 +/- 4124 pg/ml, p24 antigen passed to the fetal circulation in two of three placentas and in three of three placentas in the closed perfusion system. CONCLUSIONS: p24 antigen crossed the human placenta to the fetal circulation in what appears to be a concentration-dependent manner.

Teratogenic and embryocidal effects of Zidovudine (AZT) in sprague-dawley rats.

OBJECTIVE: The purpose of the present investigation was to analyze the effets of zidovudine on the postimplantation embryo and fetus. METHODS: Pregnant Sprague-Dawley rats were given various doses (10 mg/kg, 30 mg/kg, 150 mg/kg) of zidovudine or saline by an endotracheal tube during the period of embryogenesis (days 6-8, 9-11, 6-11 postconception). The animals were sacrificed on days 18-19 of pregnancy, and their fetuses were removed by hysterotomy. Autopsies under low (15x) and high (40x) power light microscopy were performed on all fetuses. RESULTS: There was no statistically significant difference among the groups with respect to maternal weight gain. There were more pregnancy resorptions in the group receiving high-dose zidovudine (150 mg/kg/day) throughout embryogenesis than in the control group (P = 0.001, respectively). Four major structural anomalies were noted among the 689 fetuses examined, but zidovudine was not associated with an increased frequency of congenital anomalies in rats when it was administered in doses similar to, 3-, and 15-fold higher than the regimen recommended for adult humans. The drug, however, was embryocidal in the high-dose group (P = 0.002). CONCLUSIONS: These findings are consistent with previous studies of preimplantation mouse embryos that demonstrated an embryocidal effect on preimplantation conceptuses. In summary, post-implantation embryonic zidovudine exposure was associated with significantly increased pregnancy losses (resorptions and intrauterine deaths).

The transfer of the nucleoside analog ganciclovir across the perfused human placenta.

OBJECTIVE: The purpose of this study was to compare the maternal-fetal placental transfer of the antiviral nucleoside analog ganciclovir to that of acyclovir and to investigate the mechanism of transport. STUDY DESIGN: The ex vivo human placental cotyledon model was used. Carbon 14-labeled antipyrine was used as the reference compound to determine the clearance index of both antiviral agents. Dinitrobenzylthioinosine was used as a nucleoside transport inhibitor to help determine the transfer mechanism of each agent. RESULTS: The clearance index for ganciclovir was 0.17 +/- 0.08 and 0.20 +/- 0.10 at 1 and 10 micrograms/ml maternal concentrations. This was similar to the clearance index for acyclovir, which was 0.17 +/- 0.06 and 0.18 +/- 0.12, respectively. The clearance index for ganciclovir was not significantly affected by the addition of 5 mumol/L dinitrobenzylthionosine to the perfusate (0.25 +/- 0.09 vs 0.20 +/- 0.05). The same was true for acyclovir (0.29 +/- 0.06 vs 0.22 +/- 0.07). When the closed system and maternal ganciclovir concentrations of 1.0, 10.0, and 100 micrograms/ml were used, the percent fetal levels compared with maternal levels at 1 hour were 17.2%, 19.2%, and 17.3%, respectively. For acyclovir the fetal levels were 15.6%, 9.1%, and 8.9% compared with maternal levels. CONCLUSION: The antiviral agents ganciclovir and acyclovir appear to cross the placenta by simple diffusion, at least at therapeutic levels, and this transfer is not affected by the nucleoside transport inhibitor dinitrobenzylthioinosine.

Oral amoxicillin as prophylaxis for endocarditis: what is the optimal dose?

We compared serum levels and tolerability of oral amoxicillin in 30 healthy adults who each received 2.0 g of amoxicillin and, 1 week later, 3.0 g of the same preparation. Serum levels of amoxicillin were determined at 1, 2, 4, and 6 hours following its ingestion. Mean serum levels of amoxicillin were significantly higher after 3.0-g doses than after 2.0-g doses. Levels in females were higher than in males; this was a reflection of differences in body weights. Food intake had no effect on serum levels. The 2.0-g doses resulted in adequate serum levels; 6 hours after dosing levels were still substantially higher than the MICs for oral streptococci. Three individuals (10%) experienced mild gastrointestinal side effects after they received the 3.0-g doses; no side effects were noted after the 2.0-g doses. We propose that to prevent bacterial endocarditis in adults who are at risk, a single 2.0-g dose of oral amoxicillin may be adequate prophylaxis for dental, oral, or upper respiratory tract procedures.

The ex vivo transfer of the anti-HIV nucleoside compound d4T in the human placenta.

The purpose of this study was to determine the ex vivo maternal-fetal placental transfer of 2',3'-didehydro-3'-deoxythymidine (d4T) and to compare it to the perfusion characteristics of 3'-azido-2',3-dideoxythymidine (AZT). This study used the single cotyledon perfusion system and antipyrine to determine the clearance index of this thymidine-containing anti-human immunodeficiency virus (HIV) compound. The endogenous base thymidine and the inhibitor dipyridamole were used to determine if this anti-HIV compound crossed the placenta by simple diffusion. The clearance index of d4T was 0.24 +/- 0.07 at 1.0 micrograms/ml and 0.235 +/- 0.045 at 10.0 micrograms/ml. These data suggest that the clearance index of d4T is 77-81% of AZT. The presence of high concentrations of dipyridamole and endogenous thymidine did not alter the clearance of d4T. In studies in which both the maternal and fetal circulations were closed, the accumulation in the fetal circulation was linear when the maternal concentration was in the range of 1-100 micrograms/ml. These data suggest that d4T crosses the human placenta by simple diffusion, and has similar perfusion characteristics to that of AZT.

Studies on the placental transfer of cell-free human immunodeficiency virus and p24 antigen in an ex vivo human placental model.

OBJECTIVE: We studied whether the human placenta has the structural integrity to impede transplacental passage of cell-free human immunodeficiency virus (HIV)-1 or p24 antigen from the maternal to the fetal circulation. METHODS: Nine term human placentas from uncomplicated vaginal or cesarean section deliveries were studied ex vivo with a placental perfusion apparatus to determine whether cell-free HIV-1 at 200-2000 tissue culture infectious dose (TCID50/mL) would pass to the fetal circulation. Passage of virus or p24 was assessed by infectivity titration and/or p24 antigen capture enzyme immunoassay. RESULTS: Infectious HIV-1 was not detected in any of the fetal perfusate samples taken periodically during experiments. Low concentrations of HIV-1 p24 antigen, however, were detected in fetal perfusate samples from three placentas. CONCLUSIONS: The term human placenta effectively impedes passage of cell-free HIV-1 from the maternal to the fetal circulation. However, it may be permeable to passage of p24 antigen.

Penicillin levels following the administration of benzathine penicillin G in pregnancy.

OBJECTIVE: To investigate the distribution of penicillin in the maternal-placental-fetal unit at term gestation. METHODS: Twenty-five healthy gravidas at 38-39 weeks' gestation scheduled for elective repeat cesarean delivery under spinal anesthesia received benzathine penicillin G, 2.4 million units intramuscularly (IM) preoperatively. Ten women delivered 1 day after injection, five delivered 2-3 days after, and ten delivered 7 days after. We collected maternal serum and cerebrospinal fluid, amniotic fluid (AF), and cord serum at delivery. Penicillin levels were measured using a validated agar disc diffusion method (sensitivity 0.006 micrograms/mL) with Micrococcus lutea as the test organism. RESULTS: There was no significant difference in mean penicillin levels at day 1, day 2-3, or day 7 for maternal serum, maternal cerebrospinal fluid, cord serum, or AF. The mean (+/- standard error) penicillin concentration (range 0.005-0.59 micrograms/mL) in maternal serum declined from 0.14 +/- 0.04 micrograms/mL 1 day after injection to 0.08 +/- 0.06 micrograms/mL 7 days after injection. The proportion of patients with a penicillin concentration at or above 0.018 micrograms/mL in the maternal serum declined significantly from day 1 to day 7 (P = .03). Overall, nine of 25 women (36%) had serum penicillin levels that were less than 0.018 micrograms/mL. CONCLUSION: A wide range of penicillin levels were observed in gravidas at term in the maternal serum, cerebrospinal fluid, umbilical cord serum, and AF within 1 week after 2.4 million units of benzathine penicillin G IM. We speculate that altered pharmacokinetics may affect the efficacy of this drug for prevention of congenital syphilis in the near-term gestation.

Transfer of Timentin (ticarcillin and clavulanic acid) across the in vitro perfused human placenta: comparison with other agents.

OBJECTIVES: In vitro perfusion of human placentas was used to quantify the net placental transfer of ticarcillin and clavulanic acid. STUDY DESIGN: Placentas were obtained from uncomplicated pregnancies at term. The maternal and fetal circulations were reestablished at flow rates of 17.5 ml/min and 5 ml/min, respectively. Open circulations were used to evaluate steady-state pharmacodynamics and transplacental gradient formation. Drug levels were measured by high-pressure liquid chromatography. RESULTS: The clearance index of ticarcillin was 0.037 +/- 0.004. The fetal/maternal ratio was 0.91. Therapeutic concentrations of clavulanate (2 to 6 micrograms/ml) in the maternal media resulted in undetectable transfer to the fetal compartment. By using higher levels of clavulanate, a clearance index of 0.061 +/- 0.001 (mean +/- SEM) and 1:1 fetal/maternal gradient was obtained. CONCLUSIONS: These data correspond to relatively low transfer of ticarcillin with a cord/maternal ratio of < 1. Clavulanate transfer is slightly greater. Agents with similar activity and superior transfer would optimize intrauterine treatment.

The transfer of anti-human immunodeficiency virus nucleoside compounds by the term human placenta.

OBJECTIVE: The purpose of this study was to compare the maternal-fetal placental transfer of 2',3'-dideoxyinosine and 2',3'-dideoxycytidine with that of 3'-azido-2', 3-dideoxythymidine (azidothymidine). STUDY DESIGN: The perfusion system used carbon 14-labeled antipyrine as a reference compound to determine the clearance index of each compound. The inhibitor dipyridamole and the endogenous bases were used to determine if these anti-human immunodeficiency virus compounds crossed the placenta other than by simple diffusion. RESULTS: The clearance index of azidothymidine was 0.29 +/- 0.04 at maternal concentrations of 1.0 to 10 micrograms/ml, and the clearance index of 2',3'-dideoxyinosine was 0.14 +/- 0.05, which was 48% of the clearance index of azidothymidine. The clearance index of 2',3'-dideoxyinosine was essentially identical to azidothymidine in the range from 1 to 10 micrograms/ml. The results of the closed-closed studies suggest that at therapeutic peak concentrations of 1 to 2 micrograms/ml of these compounds in the maternal circulation therapeutic levels will be reached in the fetal circulation. CONCLUSION: These anti-human immunodeficiency virus inhibitors appear to cross the placenta rapidly by simple diffusion because (1) the transfer of the drugs to the fetal circulation was not saturable even at 100 micrograms/ml, (2) there was no change in clearance index with the addition of 300 mumol/L of thymidine, inosine, cytosine, or 30 mumol/L dipyridamole, and (3) there was no accumulation against the maternal fetal or fetal maternal concentration gradient.

Effect of impaired renal function on the pharmacokinetics of coadministered cefoperazone and sulbactam.

The pharmacokinetics of cefoperazone 2 g combined with sulbactam 1 g after a single dose administered intravenously were evaluated in 24 subjects with normal and impaired renal function. Subjects were categorized into four groups based on endogenous creatinine clearance Clcr. Patients in groups 1, 2 and 3 had ClcrS of greater than 60, 31 to 60, and 10 to 30 mL/min/1.73 m2, respectively. Patients in group 4 required maintenance haemodialysis and were assumed to have Clcr less than 10 mL/min/1.73 m2. Pharmacokinetic parameters were determined by noncompartmental methods. No significant differences (P greater than 0.05) in mean peak serum cefoperazone-sulbactam concentrations for group 1 (208.4/29.0 mg/L), group 2 (199.0/34.1 mg/L), group 3 (163.2/35.0 mg/L), and group 4 (234.0/66.0 mg/L) were noted. Correlations between both total serum (r = 0.58) and renal (r = 0.35) clearance and creatinine clearances were negative for cefoperazone, although both were shown to decline with diminished renal function. Correlations between serum (r = 0.85) and renal (r = 0.72) clearances and creatinine clearance for sulbactam were, on the other hand, both positive and declined in a linear fashion. No significant differences in steady state volumes of distribution were noted for either cefoperazone (P = 0.53) or sulbactam (P = 0.85) amongst the four groups. After 24 h, urinary recovery was also comparable for both cefoperazone (P = 0.64) and sulbactam (P = 0.85) amongst the four groups. The concentrations of cefoperazone and sulbactam remained at or above the MICs (16/8 mg/L) for common bacterial pathogens for 2.5, 3, 7 and 14 h in groups 1, 2, 3 and 4, respectively.