Prediction of maternal and fetal pharmacokinetics of indomethacin in pregnancy.

AIMS: Indomethacin is used for the treatment of preterm labour, short cervices and idiopathic polyhydramnios during pregnancy. Few studies have described the pharmacokinetics (PK) of indomethacin during pregnancy. This study aimed to determine maternal and fetal PK of indomethacin during different trimesters of pregnancy using physiologically based PK (PBPK) modelling and simulations. METHODS: Full PBPK simulations were performed in nonpregnant subjects and pregnant subjects from each trimester of pregnancy at steady state using Simcyp's healthy volunteers and pregnancy PBPK model, respectively. The fetal exposures were predicted using a fetoplacental pregnancy PBPK model. The models were verified by comparing PBPK-based predictions with observed PK profiles. RESULTS: Predicted exposure (AUC0-6h ) and clearance of indomethacin in nonpregnant women and pregnant women are similar to the clinical observations. AUC0-6h of indomethacin is approximately 14, 24 and 32% lower, consistent with 18, 34 and 52% higher clearance in the first, second and third trimesters of pregnancy, respectively, compared to nonpregnant women. Predicted fetal plasma exposures increased by approximately 30% from the second trimester to the third trimester of pregnancy. CONCLUSION: A mechanistic PBPK model adequately described the maternal and the fetal PK of indomethacin during pregnancy. As the pregnancy progresses, a modest decrease (≤32%) in systemic exposures in pregnant women and a 33% increase in fetal exposures to indomethacin were predicted. Higher fetal exposures in the third trimester of pregnancy may pose safety risks to the fetus. Additional studies are warranted to understand the exposure-response relationship and provide appropriate dosing recommendations during pregnancy that consider both safety and efficacy.

Formulation effects on paclitaxel transfer and uptake in the human placenta.

Diagnosis and treatment of breast cancer in pregnancy can result in morbidity and mortality for the mother and fetus. Many new paclitaxel nanoformulations commercially available worldwide for breast cancer treatment are being adopted due to favorable dosing regimens and side effect profiles, but their transplacental transport and resultant fetal exposure remain unknown. Here, we examine three formulations: Taxol (paclitaxel dissolved in Kolliphor EL and ethanol); Abraxane (albumin nanoparticle); and Genexol-PM (polymeric micelle). In the ex vivo dually perfused human placental cotyledon, placental accumulation of Genexol-PM is higher than Taxol, and both nanoformulations have lower maternal concentrations of paclitaxel over time. In vitro studies of these formulations and fluorescent nanoparticle analogs demonstrate that Genexol-PM allows paclitaxel to overcome P-glycoprotein efflux, but Abraxane behaves as a free drug formulation. We anticipate that these findings will impact future development of rational and safe treatment strategies for pregnancy-associated breast cancer and other diseases.

Bupropion sustained release for pregnant smokers: a randomized, placebo-controlled trial.

BACKGROUND: Bupropion is used to treat depression during pregnancy. However, its usefulness as a smoking cessation aid for pregnant women is not fully known. OBJECTIVE: The objective of the study was to evaluate the preliminary efficacy of bupropion sustained release for smoking cessation during pregnancy. STUDY DESIGN: We conducted a randomized, prospective, double-blind, placebo-controlled, pilot trial. Pregnant women who smoked daily received individualized behavior counseling and were randomly assigned to a 12 week, twice-a-day treatment with 150 mg bupropion sustained release or placebo. The primary study objectives were to determine whether bupropion sustained release reduces nicotine withdrawal symptoms on the quit date and during the treatment period compared with placebo and whether it increases 7 day point prevalence abstinence at the end of the treatment period and at the end of pregnancy. RESULTS: Subjects in the bupropion (n = 30) and placebo (n = 35) groups were comparable in age, smoking history, number of daily smoked cigarettes, and nicotine dependence. After controlling for maternal age and race, bupropion sustained release reduced cigarette cravings (1.5 ± 1.1 vs 2.1 ± 1.2, P = .02) and total nicotine withdrawal symptoms (3.8 ± 4.3 vs 5.4 ± 5.1, P = .028) during the treatment period. Administration of bupropion sustained release reduced tobacco exposure, as determined by levels of carbon monoxide in exhaled air (7.4 ± 6.4 vs 9.1 ± 5.8, P = .053) and concentrations of cotinine in urine (348 ± 384 ng/mL vs 831 ± 727 ng/mL, P = .007) and increased overall abstinence rates during treatment (19% vs 2%, P = .003). However, there was no significant difference in 7 day point prevalence abstinence rates between the 2 groups at the end of medication treatment (17% vs 3%, P = .087) and at the end of pregnancy (10% vs 3%, P = .328). CONCLUSION: Individual smoking cessation counseling along with the twice-daily use of 150 mg bupropion sustained release increased smoking cessation rates and reduced cravings and total nicotine withdrawal symptoms during the treatment period. However, there was no significant difference in abstinence rates between groups at the end of medication treatment and at the end of pregnancy, likely because of the small sample size. A larger study is needed to confirm these findings and to examine the potential benefit/ risk ratio of bupropion sustained release for smoking cessation during pregnancy.

Pharmacokinetics of Bupropion and Its Pharmacologically Active Metabolites in Pregnancy.

Bupropion sustained release is used to promote smoking cessation in males and nonpregnant females. However, its efficacy as a smoking cessation aid during pregnancy is not reported. The pregnancy-associated changes in maternal physiology may alter the pharmacokinetics and pharmacodynamics of bupropion and consequently its efficacy in pregnant smokers. Therefore, the aims of this study were to determine the steady-state pharmacokinetics of bupropion during pregnancy and the effect of functional genetic variants of CYP2B6 and CYP2C19 on bupropion pharmacokinetics in pregnant women. Plasma and urine concentrations of bupropion and its metabolites hydroxybupropion (OHBUP), threohydrobupropion, and erythrohydrobupropion were determined by liquid chromatography-mass spectrometry. Subjects were genotyped for five nonsynonymous single-nucleotide polymorphisms that result in seven CYP2B6 alleles, namely *2, *3, *4, *5, *6, *7, and *9, and for CYP2C19 variants *2, *3, and *17 The present study reports that the isoform-specific effect of pregnancy on bupropion-metabolizing enzymes along with the increase of renal elimination of the drug could collectively result in a slight decrease in exposure to bupropion in pregnancy. In contrast, pregnancy-induced increase in CYP2B6-catalyzed bupropion hydroxylation did not impact the plasma levels of OHBUP, probably due to a higher rate of OHBUP glucuronidation, and renal elimination associated with pregnancy. Therefore, exposure to OHBUP, a pharmacologically active metabolite of the bupropion, appears to be similar to that of the nonpregnant state. The predicted metabolic phenotypes of CYP2B6*6 and variant alleles of CYP2C19 in pregnancy are similar to those in the nonpregnant state.

Bupropion therapy during pregnancy: the drug and its major metabolites in umbilical cord plasma and amniotic fluid.

BACKGROUND: Bupropion is used for treatment of depression during pregnancy. However, its use as a smoking cessation aid for pregnant women is currently under evaluation. OBJECTIVE: The aim of this opportunistic study was to investigate the transfer of bupropion and its major pharmacologically active metabolites, hydroxybupropion and threohydrobupropion, across the placenta in vivo. In addition, the concentrations of the drug and its metabolites were determined in the amniotic fluid. STUDY DESIGN: The following samples were collected at deliveries from 22 women taking bupropion: maternal blood (n = 22), umbilical cord venous blood (n = 22), and amniotic fluid (n = 9). The concentrations of the drug and its metabolites in blood plasma and amniotic fluid were determined by means of liquid chromatography-mass spectrometry. Placental passage was calculated as a ratio of umbilical cord venous plasma to maternal plasma concentrations. RESULTS: The levels of hydroxybupropion and threohydrobupropion in umbilical cord venous plasma were invariably lower than their corresponding concentrations in maternal plasma. The concentrations of bupropion in umbilical cord plasma were lower than in maternal plasma in the majority of the maternal-cord blood pairs. The median values of the umbilical cord venous plasma to maternal plasma ratios were: bupropion, 0.53 (interquartile range 0.35, n = 18), hydroxybupropion, 0.21 (interquartile range 0.12, n = 18), and threohydrobupropion, 0.61 (interquartile range 0.11, n = 21). In umbilical cord venous plasma, the median concentration of bupropion was 5.3 ng/mL; hydroxybupropion, 103.6 ng/mL; and threohydrobupropion, 59.6 ng/mL. Bupropion and its metabolites were detectable in the amniotic fluid but the concentrations of threohydrobupropion were higher than those in the corresponding umbilical cord venous plasma. CONCLUSION: Bupropion and its active metabolites cross the placenta to the fetal circulation. The concentrations of hydroxybupropion and threohydrobupropion in umbilical cord venous plasma were higher than bupropion concentrations suggesting a higher fetal exposure to the metabolites than the parent drug. The higher levels of threohydrobupropion in the amniotic fluid than those in umbilical cord venous plasma suggest that enzymes involved in the metabolism of bupropion to threohydrobupropion are most likely active in the fetus. The biological consequences of fetal exposure to maternally administered bupropion and/or its active metabolites via placental transfer and recirculation of the amniotic fluid are yet to be determined.

Quantitative determination of pravastatin and its metabolite 3α-hydroxy pravastatin in plasma and urine of pregnant patients by LC-MS/MS.

This report describes the development and validation of a chromatography/tandem mass spectrometry method for the quantitative determination of pravastatin and its metabolite (3α-hydroxy pravastatin) in plasma and urine of pregnant patients under treatment with pravastatin, as part of a clinical trial. The method includes a one-step sample preparation by liquid-liquid extraction. The extraction recovery of the analytes ranged between 93.8 and 99.5% in plasma. The lower limits of quantitation of the analytes in plasma samples were 0.106 ng/mL for pravastatin and 0.105 ng/mL for 3α-hydroxy pravastatin, while in urine samples they were 19.7 ng/mL for pravastatin and 2.00 ng/mL for 3α-hydroxy pravastatin. The relative deviation of this method was <10% for intra- and interday assays in plasma and urine samples, and the accuracy ranged between 97.2 and 106% in plasma, and between 98.2 and 105% in urine. The method described in this report was successfully utilized for determining the pharmacokinetics of pravastatin in pregnant patients enrolled in a pilot clinical trial for prevention of preeclampsia.

Quantitative determination of metformin, glyburide and its metabolites in plasma and urine of pregnant patients by LC-MS/MS.

This report describes the development and validation of an LC-MS/MS method for the quantitative determination of glyburide (GLB), its five metabolites (M1, M2a, M2b, M3 and M4) and metformin (MET) in plasma and urine of pregnant patients under treatment with a combination of the two medications. The extraction recovery of the analytes from plasma samples was 87-99%, and that from urine samples was 85-95%. The differences in retention times among the analytes and the wide range of the concentrations of the medications and their metabolites in plasma and urine patient samples required the development of three LC methods. The lower limit of quantitation (LLOQ) of the analytes in plasma samples was as follows: GLB, 1.02 ng/mL; its five metabolites, 0.100-0.113 ng/mL; and MET, 4.95 ng/mL. The LLOQ in urine samples was 0.0594 ng/mL for GLB, 0.984-1.02 ng/mL for its five metabolites and 30.0 µg/mL for MET. The relative deviation of this method was <14% for intra-day and inter-day assays in plasma and urine samples, and the accuracy was 86-114% in plasma, and 94-105% in urine. The method described in this report was successfully utilized for determining the concentrations of the two medications in patient plasma and urine.

Metabolism and disposition of bupropion in pregnant baboons (Papio cynocephalus).

Recent in vitro data obtained in our laboratory revealed similarities between baboons and humans in the biotransformation of bupropion (BUP) by both hepatic and placental microsomes. These data supported the use of baboons to study BUP biotransformation during pregnancy. The aim of this investigation was to determine the pharmacokinetics of BUP in baboons during pregnancy and postpartum, as well as fetal exposure to the drug after intravenous administration. Pregnant baboons (n = 5) received a single intravenous bolus dose of bupropion hydrochloride (1 mg/kg) at gestational ages 94-108 days (midpregnancy), 142-156 days (late pregnancy), and 6 weeks postpartum. Blood and urine samples were collected for 12 and 24 hours, respectively. The concentrations of BUP, hydroxybupropion (OH-BUP), threohydrobupropion, and erythrohydrobupropion in plasma were determined by liquid chromatography-tandem mass spectrometry. Relative to the postpartum period, the average midpregnancy clearance of BUP trended higher (3.6 ± 0.15 versus 2.7 ± 0.28 l/h per kg) and the average C(max) (294 ± 91 versus 361 ± 64 ng/ml) and the area under the curve (AUC) of BUP values (288 ± 22 versus 382 ± 42 h·ng/ml) trended lower. AUC(OH-BUP) also tended to be lower midpregnancy compared with postpartum (194 ± 76 versus 353 ± 165 h·ng/ml). Whereas the observed trend toward increased clearance of BUP during baboon pregnancy could be associated with a pregnancy-induced increase in its biotransformation, the trend toward increased renal elimination of OH-BUP may overshadow any corresponding change in the hydroxylation activity of CYP2B.

Transplacental transfer and distribution of pravastatin.

OBJECTIVE: The objective of the study was to determine the bidirectional transfer of pravastatin across the dually perfused term human placental lobule and its distribution between the tissue and maternal and fetal circuits. STUDY DESIGN: The transfer of pravastatin was determined in the maternal-to-fetal (n = 11) and fetal-to-maternal (n = 10) directions. Pravastatin was coperfused with its [(3)H]-isotope and the marker compound antipyrine (20 µg/mL) and its [(14)C]-isotope. The concentration of pravastatin in the perfused tissue and the maternal and fetal circuits was determined using liquid scintillation spectrometry. Inside-out vesicles prepared from placental brush border membranes were utilized to investigate the role of efflux transporters in the transplacental transfer of pravastatin. RESULTS: Pravastatin was transferred from the maternal to the fetal circuit and vice versa. In the maternal-to-fetal direction, the distribution of pravastatin at the end of experiment was as follows: 14 ± 5% of the drug was retained by the tissue, 68 ± 5% remained in the maternal circuit, and 18 ± 4% was transferred to the fetal circuit. The normalized transfer of pravastatin (clearance index) to antipyrine in the fetal-to-maternal direction (0.48 ± 0.07) was higher than its transfer in the maternal-to-fetal direction (0.36 ± 0.07, P < .01). Furthermore, pravastatin inhibited the adenosine triphosphate (ATP)-dependent uptake of the paclitaxel and estrone sulfate. CONCLUSION: The transfer of pravastatin across the dually perfused placental lobule suggests that fetal exposure to pravastatin is plausible. The higher transfer of pravastatin in the fetal-to-maternal direction than the reverse as well as its inhibition of the ATP-dependent uptake of [(3)H]-paclitaxel and [(3)H]-estrone sulfate strongly suggest the involvement of efflux transporters in decreasing its transfer across the placenta and support pravastatin's favorable pharmacokinetic profile in pregnancy.

Quantitative determination of famotidine in human maternal plasma, umbilical cord plasma and urine using high-performance liquid chromatography-mass spectrometry.

Liquid chromatography with electrospray ionization mass spectrometry for the quantitative determination of famotidine in human urine, maternal and umbilical cord plasma was developed and validated. The plasma samples were alkalized with ammonium hydroxide and extracted twice with ethyl acetate. The extraction recovery of famotidine in maternal and umbilical cord plasma ranged from 53 to 64% and 72 to 79%, respectively. Urine samples were directly diluted with the initial mobile phase then injected into the HPLC system. Chromatographic separation of famotidine was achieved by using a Phenomenex Synergi™ Hydro-RP™ column with a gradient elution of acetonitrile and 10 mm ammonium acetate aqueous solution (pH 8.3, adjusted with ammonium hydroxide). Mass spectrometric detection of famotidine was set in the positive mode and used a selected ion monitoring method. Carbon-13-labeled famotidine was used as internal standard. The calibration curves were linear (r(2) > 0.99) in the concentration ranges of 0.631-252 ng/mL for umbilical and maternal plasma samples and 0.075-30.0 µg/mL for urine samples. The relative deviation of method was <14% for intra- and inter-day assays, and the accuracy ranged between 93 and 110%. The matrix effect of famotidine in human urine, maternal and umbilical cord plasma was less than 17%.

Folate-mediated transport of nanoparticles across the placenta.

BACKGROUND: In this study, a prototype of a targeted nanocarrier for drug delivery for prenatal therapy of the developing fetus was developed and examined in vitro and ex vivo. The folate transport mechanism in the human placenta was utilized as a possible pathway for the transplacental delivery of targeted nanoparticles. METHODS: Several types of folic acid-decorated polymeric nanoparticles were synthesized and characterized. During transport studies of targeted and non-targeted fluorescent nanoparticles across the placental barrier, the apparent permeability values, uptake, transfer indices, and distribution in placental tissue were determined. RESULTS: The nanoparticles had no effect on BeWo b30 cell viability. In vitro, studies showed significantly higher apparent permeability of the targeted nanoparticles across the cell monolayers as compared to the nontargeted nanoparticles (Pe = 5.92 ± 1.44 ×10-6 cm/s for PLGA-PEG-FA vs. 1.26 ± 0.31 ×10-6 cm/s for PLGA-PEG, P < 0.05), and the transport of the targeted nanoparticles was significantly inhibited by excess folate. Ex vivo placental perfusion showed significantly greater accumulation of the targeted nanoparticles in the placental tissue (4.31 ± 0.91%/g for PLGA-PEG-FA vs. 2.07 ± 0.26%/g for PLGA-PEG). CONCLUSION: The data obtained suggested different mechanisms for the uptake and transplacental transfer of targeted versus nontargeted nanoparticles. This targeted nanoformulation may be a promising strategy for fetal drug therapy.

Transplacental transfer and metabolism of buprenorphine in preterm human placenta.

We sought to determine whether gestational age affects the transplacental transfer and metabolism of buprenorphine (BUP). Transfer of BUP (10 ng/mL) and its [ (3)H]-isotope was determined across placentas of 30 to 34 weeks of gestation utilizing the technique of dual perfusion of placental lobule. Concentration of the drug in trophoblast tissue and in maternal and fetal circuits was determined by liquid scintillation spectrometry. Microsomes prepared from placentas of 17 to 37 weeks of gestation were divided into three groups: late second, early third, and late third trimesters. Antibodies raised against human cytochrome P450 (CYP) isoforms were utilized to identify the enzyme(s) catalyzing BUP biotransformation by preterm placental microsomes. The amount of norbuprenorphine formed was determined by liquid chromatography-mass spectrometry (LC-MS). BUP transfer across the placentas of 30 to 34 weeks of gestation was similar to those at term. CYP19 antibodies caused 60% inhibition of BUP metabolism by microsomes of late second and early third trimesters and 85% by microsomes of late third trimester. The developmental changes occurring in human placenta between 30 weeks of gestation through term do not affect the transfer of BUP across human placenta. CYP19 is the major enzyme responsible for biotransformation of BUP beginning at 17 weeks of gestation until term.

Role of human placental apical membrane transporters in the efflux of glyburide, rosiglitazone, and metformin.

OBJECTIVE: Substrates of placental efflux transporters could compete for a single transporter, which could result in an increase in the transfer of each substrate to the fetal circulation. Our aim was to determine the role of placental transporters in the biodisposition of oral hypoglycemic drugs that could be used as monotherapy or in combination therapy for gestational diabetes. STUDY DESIGN: Inside-out brush border membrane vesicles from term placentas were used to determine the efflux of glyburide, rosiglitazone, and metformin by P-glycoprotein, breast cancer resistance protein, and multidrug resistance protein. RESULTS: Glyburide was transported by multidrug resistance protein (43 +/- 4%); breast cancer resistance protein (25 +/- 5%); and P-glycoprotein (9 +/- 5%). Rosiglitazone was transported predominantly by P-glycoprotein (71 +/- 26%). Metformin was transported by P-glycoprotein (58 +/- 20%) and breast cancer resistance protein (25 +/- 14%). CONCLUSION: Multiple placental transporters contribute to efflux of glyburide, rosiglitazone, and metformin. Administration of drug combinations could lead to their competition for efflux transporters.

Effect of CYP2C9 Polymorphisms on the Pharmacokinetics of Indomethacin During Pregnancy.

BACKGROUND AND OBJECTIVE: Cytochrome P450 (CYP) 2C9 catalyzes the biotransformation of indomethacin to its inactive metabolite O-desmethylindomethacin (DMI). The aim of this work was to determine the effect of CYP2C9 polymorphisms on indomethacin metabolism in pregnant women. METHODS: Plasma concentrations of indomethacin and DMI at steady state were analyzed with a validated LC-MS/MS method. DNA was isolated from subject blood and buccal smear samples. Subjects were grouped by genotype for comparisons of pharmacokinetic parameters. RESULTS: For subjects with the *1/*2 genotype, the mean steady-state apparent oral clearance (CL/Fss) of indomethacin was 13.5 ± 7.7 L/h (n = 4) and the mean metabolic ratio (AUCDMI/AUCindomethacin) was 0.291 ± 0.133. For subjects with the *1/*1 genotype, these values were 12.4 ± 2.7 L/h and 0.221 ± 0.078, respectively (n = 14). Of note, we identified one subject who was a carrier of both the *3 and *4 alleles, resulting in an amino acid change (I359P) which has not been reported previously. This subject had a metabolic ratio of 0.390 and a CL/Fss of indomethacin (24.3 L/h) that was nearly double the wild-type clearance. CONCLUSION: Although our results are limited by sample size and are not statistically significant, these data suggest that certain genetic polymorphisms of CYP2C9 may lead to an increased metabolic ratio and an increase in the clearance of indomethacin. More data are needed to assess the impact of CYP2C9 genotype on the effectiveness of indomethacin as a tocolytic agent.

Transfer of methadone across the dually perfused preterm human placental lobule.

OBJECTIVE: The objective of the study was to determine the effect of gestational age and P-glycoprotein expression on transplacental transfer of methadone. STUDY DESIGN: Dual perfusion of placental lobule was utilized. Methadone (200 ng/mL) and its [3H]-isotope were cotransfused from the maternal-to-fetal circuit with the marker compound antipyrine (20 microg/mL) and its [14C]-isotope. Concentration of the drugs in trophoblast tissue and both circuits was determined by liquid scintillation spectrometry. RESULTS: Fetal transfer rate of methadone in preterm placentas was 19 +/- 5.8%, and in term placentas it was 31 +/- 9.7% (P < .01). Clearance index of methadone in preterm placentas (0.57 +/- 0.2) was lower than in term placentas (0.95 +/- 0.3, P < .01). P-glycoprotein expression was higher in preterm than term placentas. CONCLUSION: The ex vivo transfer of methadone across preterm placentas is 30% lower than in term placentas.

The effect of esterases on 17alpha-hydroxyprogesterone caproate.

OBJECTIVE: The aim of this investigation is to determine whether 17alpha-hydroxyprogesterone caproate is hydrolyzed, in vitro, to 17alpha-hydroxyprogesterone and caproate. STUDY DESIGN: The in vitro hydrolysis of dual radioactively labeled 17alpha-hydroxy-[3H] progesterone [14C] caproate by human plasma, hepatic and placental S9 fractions as well as recombinant esterases was investigated. The formation of [3H]-17alpha-hydroxyprogesterone and [14C]-caproate were determined with the use of high-performance liquid chromatography equipped with an online radioactivity detector. The presence and activity of carboxylesterase and butyrylcholinesterase in the human-derived preparations was confirmed by the hydrolysis of their prototypic substrates p-nitrophenyl acetate, p-nitrophenyl butyrate, and butyrylthiocholine, respectively. RESULTS: The aforementioned human-derived preparations hydrolyzed p-nitrophenyl acetate, p-nitrophenyl butyrate, and butyrylthiocholine. However, when 17alpha-hydroxyprogesterone caproate was incubated with the human-derived preparations under identical experimental conditions neither [3H]-17alpha-hydroxyprogesterone nor [14C]-caproate was detected. CONCLUSION: 17Alpha-hydroxyprogesterone caproate is not hydrolyzed in vitro by the esterase enzymes present in human plasma, liver, preterm, or term placenta.

Transplacental transfer and metabolism of 17-alpha-hydroxyprogesterone caproate.

OBJECTIVE: Determine transplacental transfer and metabolism of 17-alpha-hydroxyprogesterone caproate and its distribution between the tissue and the maternal and fetal circuits of the dually perfused placental lobule. STUDY DESIGN: 17-alpha-Hydroxyprogesterone caproate (21 ng/mL) and its dual-labeled isotope, 17-alpha-hydroxy-[(3)H] progesterone [(14)C] caproate were added to the maternal circuit. The concentrations of the drug and its metabolite in trophoblast tissue and both circuits were determined by high performance liquid chromatography and liquid scintillation spectrometry. RESULTS: 17-alpha-Hydroxyprogesterone caproate was transferred from the maternal to fetal circuit. After a 4-hour perfusion period, a metabolite of 17-alpha-hydroxyprogesterone caproate that retained both progesterone and caproate moieties was identified in the tissue and the maternal and fetal circuits. Neither 17-alpha-hydroxyprogesterone caproate nor its metabolite, at the concentrations tested, had adverse effect on determined viability and functional parameters of placental tissue. CONCLUSION: 17-alpha-Hydroxyprogesterone caproate was metabolized by term placental lobule during its perfusion and both parent compound and its metabolite(s) transferred to the fetal circuit.

Effect of albumin on transplacental transfer and distribution of rosiglitazone and glyburide.

OBJECTIVE: The aims of this investigation were (i) to determine the rate and extent of rosiglitazone transfer across term human placenta, and (ii) to determine the effect of human serum albumin (HSA) on rosiglitazone and glyburide transfer and distribution. METHODS: These aims were achieved by utilizing the technique of dual perfusion of placental lobule (DPPL). Each hypoglycemic drug was coperfused with the marker compound antipyrine (AP). In each experiment, the [3H]-isotope of the hypoglycemic drug and the [14C]-isotope of AP were added to enhance the detection limits of each drug. Human serum albumin (HSA) was added to both the maternal and fetal circuits in the experiments in which it was investigated. RESULTS: Transplacental transfer of rosiglitazone and glyburide from the maternal to fetal circuits in media devoid of HSA was similar. However, the addition of HSA to the maternal and fetal circuits had different effects on the transfer and distribution of the two drugs, though their binding to HSA (99.8%) was almost identical. HSA increased the maternal (M) to fetal (F) transfer of rosiglitazone, as revealed by an increase in its F/M concentration ratio from 0.17 +/- 0.01 (in the absence of albumin) to 0.33 +/- 0.07 (p < 0.001). Moreover, the addition of albumin decreased the amount of rosiglitazone retained by placental tissue from 539 +/- 148 to 60 +/- 8 ng/g (p < 0.001). Conversely, the addition of HSA to the perfusion media resulted in a decrease in glyburide transfer, as revealed by the change of its F/M concentration ratio from 0.09 +/- 0.02 (in the absence of albumin) to 0.03 +/- 0.01 (p < 0.01). However, similar to rosiglitazone, glyburide retention by the tissue decreased from 103 +/- 26 to 19 +/- 6 ng/g (p < 0.001). CONCLUSIONS: These data indicate that the binding of the two drugs to albumin, though similar, is only one of the factors that could affect their placental transfer and distribution.

Determination of the Transplacental Transfer of Paclitaxel and Antipyrine by High Performance Liquid Chromatography Coupled with Photodiode Array Detector.

Ex vivo placental perfusion experiments are important in understanding the quantity and mechanisms of xenobiotic transport to the fetus during pregnancy. Our study demonstrates that paclitaxel and antipyrine concentrations in placental perfusion medium containing physiological concentrations of human serum albumin during pregnancy (30 mg/mL) can be quantified by RP-HPLC and UV detection. A liquid-liquid extraction method was developed for the quantification of paclitaxel and celecoxib (internal standard) from perfusion medium. Antipyrine, which is a necessary marker in placental perfusions for determining the validity of experiments and calculating the clearance index of xenobiotics, was also analyzed by HPLC and UV detection. Antipyrine concentrations were determined by HPLC after precipitating the perfusion medium in acetonitrile and separating the precipitated proteins by centrifugation. Concentrations were fitted to linear regressions with R2 values approaching 1. Lower limits of detection for paclitaxel and antipyrine were 100 ng/mL and 200 ng/mL, respectively. Both methods demonstrated high intra-day and inter-day precision and trueness. Additionally, the use of these methods was demonstrated in a placental perfusion experiment using Taxol® (paclitaxel dissolved in Cremophor-EL). The fetal transfer rate of Taxol was 6.6% after 1 hour.

Kinetics of glyburide metabolism by hepatic and placental microsomes of human and baboon.

Glyburide (glibenclamide) is under investigation for treatment of gestational diabetes. Two metabolites of glyburide have been previously identified in patients, namely, 4-trans-(M1) and 3-cis-(M2) hydroxycyclohexyl glyburide. Recently, the metabolism of glyburide by microsomes of liver and placenta from humans and baboons revealed the formation of four additional metabolites: 4-cis-(M2a), 3-trans-(M3), and 2-trans-(M4) hydroxycyclohexyl glyburide, and ethyl-hydroxy glyburide (M5). The aim of this investigation was to determine the kinetics for the metabolism of glyburide by cytochrome P450 (CYP) isozymes of human and baboon placental and hepatic microsomes. The metabolism of glyburide by microsomes from the four organs revealed saturation kinetics and apparent K(m) values between 4 and 12 microM. However, the rates for formation of the metabolites varied between organs and species. M1 was the major metabolite (36% of total), formed by human hepatic microsomes with V(max) of 80+/-13 pmol mg protein(-1)min(-1), and together with M2, accounted for only 51% of the total. M5 was the major metabolite (87%) formed by human placental microsomes with V(max) of 11 pmol mg protein(-1)min(-1). In baboon liver, M5 had the highest rate of formation (V(max) 135+/-32 pmol mg protein(-1)min(-1), 39% of total), and in its placenta, was M4 (V(max) 0.7+/-0.1 pmol mg protein(-1)min(-1), 65%). The activity of human and baboon hepatic microsomes in metabolizing glyburide was similar, but the activity of human and baboon placental microsomes was 7% and 0.3% of their respective hepatic microsomes. The data obtained suggest that more than 1 CYP isozyme is responsible for catalyzing the hydroxylation of glyburide.