Temporal changes in drug metabolism (CYP1A2, CYP2D6 and CYP3A Activity) during pregnancy

Pharmacokinetic properties of artemether, dihydroartemisinin, lumefantrine, and quinine in pregnant women with uncomplicated plasmodium falciparum malaria in Uganda

Pregnancy alters the pharmacokinetic properties of many drugs used in the treatment of malaria, usually resulting in lower drug exposures. This increases the risks of treatment failure, adverse outcomes for the fetus, and the development of resistance. The pharmacokinetic properties of artemether and its principal metabolite dihydroartemisinin (n = 21), quinine (n = 21), and lumefantrine (n = 26) in pregnant Ugandan women were studied. Lumefantrine pharmacokinetics in a nonpregnant control group (n = 17) were also studied. Frequently sampled patient data were evaluated with noncompartmental analysis. No significant correlation was observed between estimated gestational age and artemether, dihydroartemisinin, lumefantrine, or quinine exposures. Artemether/dihydroartemisinin and quinine exposures were generally low in these pregnant women compared to values reported previously for nonpregnant patients. Median day 7 lumefantrine concentrations were 488 (range, 30.7 to 3,550) ng/ml in pregnant women compared to 720 (339 to 2,150) ng/ml in nonpregnant women (P = 0.128). There was no statistical difference in total lumefantrine exposure or maximum concentration. More studies with appropriate control groups in larger series are needed to characterize the degree to which pregnant women are underdosed with current antimalarial dosing regimens.

Drug metabolism and transport during pregnancy: how does drug disposition change during pregnancy and what are the mechanisms that cause such changes?

There is increasing evidence that pregnancy alters the function of drug-metabolizing enzymes and drug transporters in a gestational-stage and tissue-specific manner. In vivo probe studies have shown that the activity of several hepatic cytochrome P450 enzymes, such as CYP2D6 and CYP3A4, is increased during pregnancy, whereas the activity of others, such as CYP1A2, is decreased. The activity of some renal transporters, including organic cation transporter and P-glycoprotein, also appears to be increased during pregnancy. Although much has been learned, significant gaps still exist in our understanding of the spectrum of drug metabolism and transport genes affected, gestational age-dependent changes in the activity of encoded drug metabolizing and transporting processes, and the mechanisms of pregnancy-induced alterations. In this issue of Drug Metabolism and Disposition, a series of articles is presented that address the predictability, mechanisms, and magnitude of changes in drug metabolism and transport processes during pregnancy. The articles highlight state-of-the-art approaches to studying mechanisms of changes in drug disposition during pregnancy, and illustrate the use and integration of data from in vitro models, animal studies, and human clinical studies. The findings presented show the complex inter-relationships between multiple regulators of drug metabolism and transport genes, such as estrogens, progesterone, and growth hormone, and their effects on enzyme and transporter expression in different tissues. The studies provide the impetus for a mechanism- and evidence-based approach to optimally managing drug therapies during pregnancy and improving treatment outcomes.

A simplified PBPK modeling approach for prediction of pharmacokinetics of four primarily renally excreted and CYP3A metabolized compounds during pregnancy

During pregnancy, a drug's pharmacokinetics may be altered and hence anticipation of potential systemic exposure changes is highly desirable. Physiologically based pharmacokinetics (PBPK) models have recently been used to influence clinical trial design or to facilitate regulatory interactions. Ideally, whole-body PBPK models can be used to predict a drug's systemic exposure in pregnant women based on major physiological changes which can impact drug clearance (i.e., in the kidney and liver) and distribution (i.e., adipose and fetoplacental unit). We described a simple and readily implementable multitissue/organ whole-body PBPK model with key pregnancy-related physiological parameters to characterize the PK of reference drugs (metformin, digoxin, midazolam, and emtricitabine) in pregnant women compared with the PK in nonpregnant or postpartum (PP) women. Physiological data related to changes in maternal body weight, tissue volume, cardiac output, renal function, blood flows, and cytochrome P450 activity were collected from the literature and incorporated into the structural PBPK model that describes HV or PP women PK data. Subsequently, the changes in exposure (area under the curve (AUC) and maximum concentration (C max)) in pregnant women were simulated. Model-simulated PK profiles were overall in agreement with observed data. The prediction fold error for C max and AUC ratio (pregnant vs. nonpregnant) was less than 1.3-fold, indicating that the pregnant PBPK model is useful. The utilization of this simplified model in drug development may aid in designing clinical studies to identify potential exposure changes in pregnant women a priori for compounds which are mainly eliminated renally or metabolized by CYP3A4.

Interpreting tacrolimus concentrations during pregnancy and postpartum

Pregnancy after solid organ transplantation, although considered high risk for maternal, fetal, and neonatal complications, has been quite successful. Tacrolimus pharmacokinetic changes during pregnancy make interpretation of whole blood trough concentrations particularly challenging. There are multiple factors that can increase the fraction of unbound tacrolimus, including but not limited to low albumin concentration and low red blood cell count. The clinical titration of dosage to maintain whole blood tacrolimus trough concentrations in the usual therapeutic range can lead to elevated unbound concentrations and possibly toxicity in pregnant women with anemia and hypoalbuminemia. Measurement of plasma or unbound tacrolimus concentrations for pregnant women might better reflect the active form of the drug, although these are technically challenging and often unavailable in usual clinical practice. Tacrolimus crosses the placenta with in utero exposure being approximately 71% of maternal blood concentrations. The lower fetal blood concentrations are likely due to active efflux transport of tacrolimus from the fetus toward the mother by placental P-glycoprotein. To date, tacrolimus has not been linked to congenital malformations but can cause reversible nephrotoxicity and hyperkalemia in the newborn. In contrast, very small amounts of tacrolimus are excreted in the breast milk and are unlikely to elicit adverse effects in the nursing infant.

Pharmacogenetics and other reasons why drugs can fail in pregnancy: higher dose or different drug?

Changes in maternal physiology during pregnancy can alter the absorption, distribution, and clearance of many drugs. When presented with a clinical situation in which it does not appear that a prescribed drug is working, clinicians must either change drugs or increase the dose of the current drug to achieve the desired clinical effect. A case highlighting antihypertensive medication in pregnancy and the effect of changed drug-metabolizing enzymes is presented. Understanding pregnancy's effect on drug-metabolizing enzymes, transporters, and receptors can help clinicians make individualized pharmacotherapeutic decisions for patients. Pharmacogenetics potentially can aid clinicians in treating pregnant women in the future as more data are generated and individualized therapeutic models are constructed.

Dosing adjustments in postpartum patients maintained on buprenorphine or methadone

Scant scientific attention has been given to examining the need for agonist medication dose changes in the postpartum period. Study objectives were: 1) to determine the need for medication dose adjustments in participants stabilized on buprenorphine or methadone 3 weeks before and 4 weeks after delivery, and 2) to evaluate the need for methadone dose adjustments during the first 7 days in participants transferred from buprenorphine to methadone at 5 weeks postpartum. Participants were opioid-dependent pregnant women who had completed a randomized, double-blind, double-dummy, flexible dosing comparison of buprenorphine to methadone. Participants received a stable dose of methadone (N = 10) or buprenorphine (N = 8) before and 4 weeks after delivery. Buprenorphine-maintained participants were transferred to methadone at 5 weeks postpartum. There were no significant differences predelivery and/or postdelivery between the buprenorphine and methadone conditions in the mean ratings of dose adequacy, "liking," "hooked," and "craving" of heroin or cocaine. Patient response to the conversion from buprenorphine to methadone seems variable. Buprenorphine-maintained participants required dose changes postpartum only after they transferred to methadone. Regardless of type of medication, postpartum patients should be monitored for signs of overmedication.

Protein binding of lopinavir and ritonavir during 4 phases of pregnancy: implications for treatment guidelines

OBJECTIVE

To investigate the intraindividual pharmacokinetics (PKs) of total (protein bound plus unbound) and unbound lopinavir/ritonavir (LPV/RTV) and to assess whether the pediatric formulation (100 mg/25 mg) can overcome any pregnancy-associated changes.

DESIGN

Prospective longitudinal PK study.

METHODS

HIV-infected pregnant antiretroviral therapy-naive and experienced women receiving LPV/RTV 400 mg/100 mg tablets twice daily. Intensive PK evaluations were performed at 20-24 weeks (PK1), 30 weeks (PK2) followed by empiric dose increase using the pediatric formulation (100 mg/25 mg twice daily), 32 weeks (PK3), and 8 weeks postpartum (PK4).

RESULTS

Twelve women completed prespecified PK evaluations. Median (range) age was 28 (18-35) years and baseline BMI was 32 (19-41) kg/m. During pregnancy, total area under the time concentration (AUC0-12h) for LPV was significantly lower than postpartum (PK1, PK2, or PK3 vs. PK4, P = 0.005). Protein-unbound LPV AUC0-12h remained unchanged during pregnancy [PK1: 1.6 (1.3-1.9) vs. PK2: 1.6 (1.3-1.9) μg·h/mL, P = 0.4] despite a 25% dose increase [PK2 vs. PK3: 1.8 (1.3-2.1) μg·h/mL, P = 0.5]. Protein-unbound LPV predose concentrations (C12h) did not significantly change despite dose increase [PK2: 0.10 (0.08-0.15) vs. PK3: 0.12 (0.10-0.15) μg/mL, P = 0.09]. Albumin and LPV AUC0-12h fraction unbound were correlated (rs = 0.3, P = 0.03).

CONCLUSIONS

Total LPV exposure was significantly decreased throughout pregnancy despite the increased dose. However, the exposure of unbound LPV did not change significantly regardless of trimester or dose. Predose concentrations of unbound LPV were not affected by the additional dose and were 70-fold greater than the minimum efficacy concentration. These findings suggest dose adjustments may not be necessary in all HIV-infected pregnant women.

Pharmacokinetics of tacrolimus during pregnancy

BACKGROUND

Information on the pharmacokinetics of tacrolimus during pregnancy is limited to case reports despite the increasing number of pregnant women being prescribed tacrolimus for immunosuppression.

METHODS

Blood, plasma, and urine samples were collected over 1 steady-state dosing interval from women treated with oral tacrolimus during early to late pregnancy (n = 10) and postpartum (n = 5). Total and unbound tacrolimus as well as metabolite concentrations in blood and plasma were assayed by a validated liquid chromatography/mass spectrometry/mass spectrometry (LC/MS/MS) method. A mixed-effect linear model was used for comparison across gestational age and using postpartum as the reference group.

RESULTS

The mean oral clearance (CL/F) based on whole-blood tacrolimus concentration was 39% higher during mid-pregnancy and late pregnancy compared with postpartum (47.4 ± 12.6 vs. 34.2 ± 14.8 L/h, P < 0.03). Tacrolimus-free fraction increased by 91% in plasma (f(P)) and by 100% in blood (f(B)) during pregnancy (P = 0.0007 and 0.002, respectively). Increased fP was inversely associated with serum albumin concentration (r = -0.7, P = 0.003), which decreased by 27% during pregnancy. Pregnancy-related changes in f(P) and f(B) contributed significantly to the observed gestational increase in tacrolimus whole-blood CL/F (r² = 0.36 and 0.47, respectively, P < 0.01). In addition, tacrolimus whole-blood CL/F was inversely correlated with both hematocrit and red blood cell counts, suggesting that binding of tacrolimus to erythrocytes restricts its availability for metabolism. Treating physicians increased tacrolimus dosages in study participants during pregnancy by an average of 45% to maintain tacrolimus whole-blood trough concentrations in the therapeutic range. This led to striking increases in unbound tacrolimus trough concentrations and unbound area under the concentration-time curve, by 112% and 173%, respectively, during pregnancy (P = 0.02 and 0.03, respectively).

CONCLUSIONS

Tacrolimus pharmacokinetics are altered during pregnancy. Dose adjustment to maintain whole-blood tacrolimus concentration in the usual therapeutic range during pregnancy increases circulating free drug concentrations, which may impact clinical outcomes.

Potential effect of pharmacogenetics on maternal, fetal and infant antiretroviral drug exposure during pregnancy and breastfeeding

Mother-to-child-transmission rates of HIV in the absence of any intervention range between 20 and 45%. However, the provision of antiretroviral drugs (ARVs) during pregnancy, delivery and breastfeeding can reduce HIV transmission to less than 2%. Physiological changes during pregnancy can influence ARV disposition. Associations between SNPs in genes coding for metabolizing enzymes, and/or transporters, and ARVs disposition are well described; however, relatively little is known about the influence of these SNPs on ARV pharmacokinetics during pregnancy and lactation as well as their effect on distribution into the fetal compartment and breast milk excretion. Differences in maternal, fetal and infant ARV exposure due to SNPs may affect the efficacy and safety of ARVs used to prevent mother-to-child-transmission. The aim of this review is to provide an update on the effect of pregnancy-induced changes on the pharmacokinetics of ARVs and highlight the potential role of pharmacogenetics.

A pregnancy physiologically based pharmacokinetic (p-PBPK) model for disposition of drugs metabolized by CYP1A2, CYP2D6 and CYP3A4

AIMS

Pregnant women are usually not part of the traditional drug development programme. Pregnancy is associated with major biological and physiological changes that alter the pharmacokinetics (PK) of drugs. Prediction of the changes to drug exposure in this group of patients may help to prevent under- or overtreatment. We have used a pregnancy physiologically based pharmacokinetic (p-PBPK) model to assess the likely impact of pregnancy on three model compounds, namely caffeine, metoprolol and midazolam, based on the knowledge of their disposition in nonpregnant women and information from in vitro studies.

METHODS

A perfusion-limited form of a 13-compartment full-PBPK model (Simcyp® Simulator) was used for the nonpregnant women, and this was extended to the pregnant state by applying known changes to all model components (including the gestational related activity of specific cytochrome P450 enzymes) and through the addition of an extra compartment to represent the fetoplacental unit. The uterus and the mammary glands were grouped into the muscle compartment. The model was implemented in Matlab Simulink and validated using clinical observations.

RESULTS

The p-PBPK model predicted the PK changes of three model compounds (namely caffeine, metoprolol and midazolam) for CYP1A2, CYP2D6 and CYP3A4 during pregnancy within twofold of observed values. The changes during the third trimester were predicted to be a 100% increase, a 30% decrease and a 35% decrease in the exposure of caffeine, metoprolol and midazolam, respectively, compared with the nonpregnant women.

CONCLUSIONS

In the absence of clinical data, the in silico prediction of PK behaviour during pregnancy can provide a valuable aid to dose adjustment in pregnant women. The performance of the model for drugs metabolized by a single enzyme to different degrees (high and low extraction) and for drugs that are eliminated by several different routes warrants further study.

The impact of glucocorticoid polymorphisms on markers of neonatal respiratory disease after antenatal betamethasone administration

OBJECTIVE

We previously demonstrated that maternal and fetal genotypes are associated independently with neonatal respiratory distress syndrome. The objective of the current study was to determine the impact of maternal and fetal single-nucleotide polymorphisms (SNPs) in key betamethasone pathways on respiratory outcomes that serve as markers for severity of disease.

STUDY DESIGN

DNA was obtained from women who were given betamethasone and from their infants. Samples were genotyped for 73 exploratory drug metabolism and glucocorticoid pathway SNPs. Clinical variables and neonatal outcomes were obtained. Logistic regression analysis that controlled for relevant clinical variables to determine SNP impact on bronchopulmonary dysplasia (BPD), the need for respiratory support, and surfactant therapy use was performed.

RESULTS

Data from 109 women who delivered 117 infants were analyzed: 14.5% of the infants experienced BPD; 70.8% of the infants needed some respiratory support after birth, and 27.5% of the infants needed surfactant therapy. In a multivariable regression analysis, gestational age at delivery was associated with most neonatal respiratory outcomes (P ≤ .01), and chorioamnionitis was associated with BPD (P < .03). The following genotypes were associated with respiratory severity outcomes: BPD-fetal Importin 13 gene (IPO13; rs4448553; odds ratio [OR], 0.01; 95% confidence interval [CI], 0.00-0.92); surfactant use-maternal IPO13 (rs2428953 and 2486014; OR, 13.8; 95% CI, 1.80-105.5; and OR, 35.5; 95% CI, 1.71-736.6, respectively).

CONCLUSION

Several discrete maternal and fetal SNPs in the IPO13 family may be associated with neonatal respiratory outcomes after maternal antenatal corticosteroid treatment for anticipated preterm birth.

Pharmacokinetic optimization of antiretroviral therapy in pregnancy

Antiretroviral therapy suppresses replication of HIV allowing restoration and/or preservation of the immune system. Providing combination antiretroviral therapy during pregnancy can treat maternal HIV infection and/or reduce perinatal HIV transmission. However, providing treatment to pregnant women is challenging due to physiological changes that can alter antiretroviral pharmacokinetics. Suboptimal drug exposure can result in HIV RNA rebound, the selection of resistant virus or an increased risk of HIV-1 transmission to the infant. Increased drug exposure can produce unwarranted maternal adverse effects and/or fetal toxicity. Subsequently, dose adjustments may be necessary during pregnancy to achieve comparable antiretroviral exposure to non-pregnant adults. For several antiretrovirals, systemic exposure is decreased during the last trimester of pregnancy. By 6-12 weeks postpartum, concentrations return to those prior to pregnancy. Also, the extent of antiretroviral placental transfer to the fetus and degree of antiretroviral excretion into breast milk varies within, and between, antiretroviral drug classes. It is necessary to consider the pharmacological characteristics of each antiretroviral when optimizing combination therapy during pregnancy to treat maternal HIV infection and prevent perinatal HIV transmission.

A physiologically based pharmacokinetic model to predict disposition of CYP2D6 and CYP1A2 metabolized drugs in pregnant women

Conducting pharmacokinetic (PK) studies in pregnant women is challenging. Therefore, we asked if a physiologically based pharmacokinetic (PBPK) model could be used to evaluate different dosing regimens for pregnant women. We refined and verified our previously published pregnancy PBPK model by incorporating cytochrome P450 CYP1A2 suppression (based on caffeine PK) and CYP2D6 induction (based on metoprolol PK) into the model. This model accounts for gestational age-dependent changes in maternal physiology and hepatic CYP3A activity. For verification, the disposition of CYP1A2-metabolized drug theophylline (THEO) and CYP2D6-metabolized drugs paroxetine (PAR), dextromethorphan (DEX), and clonidine (CLO) during pregnancy was predicted. Our PBPK model successfully predicted THEO disposition during the third trimester (T3). Predicted mean postpartum to third trimester (PP:T3) ratios of THEO area under the curve (AUC), maximum plasma concentration, and minimum plasma concentration were 0.76, 0.95, and 0.66 versus observed values 0.75, 0.89, and 0.72, respectively. The predicted mean PAR steady-state plasma concentration (Css) ratio (PP:T3) was 7.1 versus the observed value 3.7. Predicted mean DEX urinary ratio (UR) (PP:T3) was 2.9 versus the observed value 1.9. Predicted mean CLO AUC ratio (PP:T3) was 2.2 versus the observed value 1.7. Sensitivity analysis suggested that a 100% induction of CYP2D6 during T3 was required to recover the observed PP:T3 ratios of PAR Css, DEX UR, and CLO AUC. Based on these data, it is prudent to conclude that the magnitude of hepatic CYP2D6 induction during T3 ranges from 100 to 200%. Our PBPK model can predict the disposition of CYP1A2, 2D6, and 3A drugs during pregnancy.

Clinical interventions for women with schizophrenia: pregnancy

OBJECTIVE

A comprehensive treatment program for schizophrenia needs to include services to women of childbearing age that address contraception, pregnancy, and postpartum issues, as well as safe and effective parenting. To update knowledge in these areas, a summary of the recent qualitative and quantitative literature was undertaken.

METHOD

The search terms 'sexuality,''contraception,''pregnancy,''postpartum,''custody,' and 'parenting' were entered into PubMed, PsycINFO, and SOCINDEX along with the terms 'schizophrenia' and 'antipsychotic.' Publications in English for all years subsequent to 2000 were retrieved and their reference lists further searched in an attempt to arrive at a distillation of useful clinical recommendations.

RESULTS

The main recommendations to care providers are as follows: take a sexual history and initiate discussion about intimate relationships and contraception with all women diagnosed with schizophrenia. During pregnancy, adjust antipsychotic dose to clinical status, link the patient with prenatal care services, and help her prepare for childbirth. There are pros and cons to breastfeeding while on medication, and these need thorough discussion. During the postpartum period, mental health home visits should be provided. Parenting support is critical.

CONCLUSION

The comprehensive treatment of schizophrenia in women means remembering that all women of childbearing age are potential new mothers.

Pharmacologic evidence to support clinical decision making for peripartum methadone treatment

RATIONALE

Limited pharmacological data are available to guide methadone treatment during pregnancy and postpartum.

OBJECTIVES

Study goals were to (1) characterize changes in methadone dose across childbearing, (2) determine enantiomer-specific methadone withdrawal kinetics from steady state during late pregnancy, (3) assess enantiomer-specific changes in methadone level/dose (L/D) ratios across childbearing, and (4) explore relationships between CYP2B6, CYP2C19, and CYP3A4 single-nucleotide polymorphisms and maternal dose, plasma concentration, and L/D.

METHODS

Methadone dose changes and timed plasma samples were obtained for women on methadone (n = 25) followed prospectively from third trimester of pregnancy to 3 months postpartum.

RESULTS

Participants were primarily white, Medicaid insured, and multiparous. All women increased their dose from first to end of second trimester (mean peak increase = 23 mg/day); 71 % of women increased from second trimester to delivery (mean peak increase = 19 mg/day). Half took a higher dose 3 months postpartum than at delivery despite significantly larger clearance during late pregnancy. Third trimester enantiomer-specific methadone half-lives (range R-methadone 14.7-24.9 h; S-methadone, 8.02-18.9 h) were about half of those reported in non-pregnant populations. In three women with weekly 24-h methadone levels after delivery, L/D increased within 1-2 weeks after delivery. Women with the CYP2B6 Q172 variant GT genotype have consistently higher L/D values for S-methadone across both pregnancy and postpartum.

CONCLUSIONS

Most women require increases in methadone dose across pregnancy. Given the shorter half-life and larger clearances during pregnancy, many pregnant women may benefit from split methadone dosing. L/D increases quickly after delivery and doses should be lowered rapidly after delivery.

Atazanavir pharmacokinetics, efficacy and safety in pregnancy: a systematic review

BACKGROUND

For some antiretroviral therapies, drug concentrations are reduced during pregnancy, potentially compromising effective virological suppression.

METHODS

Data on atazanavir boosted with ritonavir in pregnancy are reviewed.

RESULTS

With standard atazanavir/ritonavir 300/100 mg once-daily dosing: atazanavir area-under-the-concentration-time curves were reduced during pregnancy in most studies, but overall interpretation differed according to the data used for comparison; atazanavir concentration 24 h post-dose was maintained >150 ng/ml in 97.6% of women; no instance of mother-to-child transmission occurred in treatment-adherent mothers; and infant hyperbilirubinaemia was not elevated beyond levels expected in the neonatal period.

CONCLUSIONS

With concurrent medications that reduce atazanavir drug concentrations, optimal therapy during pregnancy may require once-daily atazanavir/ritonavir 400/100 mg; however, using this dose during the third trimester doubled maternal grade 3-4 hyperbilirubinaemia rates.

Gestational age-dependent changes in gene expression of metabolic enzymes and transporters in pregnant mice

Pregnancy-induced changes in drug pharmacokinetics can be explained by changes in expression of drug-metabolizing enzymes and transporters and/or normal physiology. In this study, we determined gestational age-dependent expression profiles for all metabolic enzyme and transporter genes in the maternal liver, kidney, small intestine, and placenta of pregnant mice by microarray analysis. We specifically examined the expression of genes important for xenobiotic, bile acid, and steroid hormone metabolism and disposition, namely, cytochrome P450s (Cyp), UDP-glucuronosyltranserases (Ugt), sulfotransferases (Sult), and ATP-binding cassette (Abc), solute carrier (Slc), and solute carrier organic anion (Slco) transporters. Few Ugt and Sult genes were affected by pregnancy. Cyp17a1 expression in the maternal liver increased 3- to 10-fold during pregnancy, which was the largest observed change in the maternal tissues. Cyp1a2, most Cyp2 isoforms, Cyp3a11, and Cyp3a13 expression in the liver decreased on gestation days (gd) 15 and 19 compared with nonpregnant controls (gd 0). In contrast, Cyp2d40, Cyp3a16, Cyp3a41a, Cyp3a41b, and Cyp3a44 in the liver were induced throughout pregnancy. In the placenta, Cyp expression on gd 10 and 15 was upregulated compared with gd 19. Notable changes were also observed in Abc and Slc transporters. Abcc3 expression in the liver and Abcb1a, Abcc4, and Slco4c1 expression in the kidney were downregulated on gd 15 and 19. In the placenta, Slc22a3 (Oct3) expression on gd 10 was 90% lower than that on gd 15 and 19. This study demonstrates important gestational age-dependent expression of metabolic enzyme and transporter genes, which may have mechanistic relevance to drug disposition in human pregnancy.

Hepatic Cyp2d and Cyp26a1 mRNAs and activities are increased during mouse pregnancy

There is considerable evidence that drug disposition is altered during human pregnancy and based on probe drug studies, CYP2D6 activity increases during human pregnancy. The aim of this study was to determine whether the changes of CYP2D6 activity observed during human pregnancy could be replicated in the mouse, and explore possible mechanisms of increased CYP2D6 activity during pregnancy. Cyp2d11, Cyp2d22, Cyp2d26 and Cyp2d40 mRNA was increased (P < 0.05) on gestational days (GD) 15 and 19 compared with the non-pregnant controls. There was no change (P > 0.05) in Cyp2d9 and Cyp2d10 mRNA. In agreement with the increased Cyp2d mRNA, Cyp2d-mediated dextrorphan formation from dextromethorphan was increased 2.7-fold (P < 0.05) on GD19 (56.8±39.4 pmol/min/mg protein) when compared with the non-pregnant controls (20.8±11.2 pmol/min/mg protein). An increase in Cyp26a1 mRNA (10-fold) and retinoic acid receptor (Rar)β mRNA (2.8-fold) was also observed during pregnancy. The increase in Cyp26a1 and Rarβ mRNA during pregnancy indicates increased retinoic acid signaling in the liver during pregnancy. A putative retinoic acid response element was identified within the Cyp2d40 promoter and the mRNA of Cyp2d40 correlated (P < 0.05) with Cyp26a1 and Rarβ. These results show that Cyp2d mRNA is increased during mouse pregnancy the and mouse may provide a suitable model to investigate the mechanisms underlying the increased clearance of CYP2D6 probes observed during human pregnancy. Our findings also suggest that retinoic acid signaling in the liver is increased during pregnancy, which may have broader implications to energy homeostasis in the liver during pregnancy.

A Semi-Mechanistic Metabolism Model of CYP3A Substrates in Pregnancy: Predicting Changes in Midazolam and Nifedipine Pharmacokinetics

Physiological changes in pregnancy, including changes in body composition and metabolic enzyme activity, can alter drug pharmacokinetics. A semi-mechanistic metabolism model was developed to describe the pharmacokinetics of two cytochrome P450 3A (CYP3A) substrates, midazolam and nifedipine, in obstetrics patients. The model parameters were optimized to fit the data of oral midazolam pharmacokinetics in pregnant women, by increasing CYP3A-induced hepatic metabolism 1.6-fold in the model with no change in gut wall metabolism. Fetal metabolism had a negligible effect on maternal plasma drug concentrations. Validation of the model was performed by applying changes in volume of distribution and metabolism, consistent with those observed for midazolam, to the pharmacokinetics parameters of immediate-release nifedipine in healthy volunteers. The predicted steady-state areas under the concentration–time curve (AUCs) for nifedipine were within 15% of the data observed in pregnant women undergoing treatment for preterm labor. This model predicts the pharmacokinetics of two CYP3A substrates in pregnancy, and may be applicable to other CYP3A substrates as well.

A PBPK Model to Predict Disposition of CYP3A-Metabolized Drugs in Pregnant Women: Verification and Discerning the Site of CYP3A Induction

Besides logistical and ethical concerns, evaluation of safety and efficacy of medications in pregnant women is complicated by marked changes in pharmacokinetics (PK) of drugs. For example, CYP3A activity is induced during the third trimester (T₃). We explored whether a previously published physiologically based pharmacokinetic (PBPK) model could quantitatively predict PK profiles of CYP3A-metabolized drugs during T₃, and discern the site of CYP3A induction (i.e., liver, intestine, or both). The model accounted for gestational age-dependent changes in maternal physiological function and hepatic CYP3A activity. For model verification, mean plasma area under the curve (AUC), peak plasma concentration (C_max), and trough plasma concentration (C_min) of midazolam (MDZ), nifedipine (NIF), and indinavir (IDV) were predicted and compared with published studies. The PBPK model successfully predicted MDZ, NIF, and IDV disposition during T₃. A sensitivity analysis suggested that CYP3A induction in T₃ is most likely hepatic and not intestinal. Our PBPK model is a useful tool to evaluate different dosing regimens during T₃ for drugs cleared primarily via CYP3A metabolism.

Population pharmacokinetics of Artemether and dihydroartemisinin in pregnant women with uncomplicated Plasmodium falciparum malaria in Uganda

Background

Malaria in pregnancy increases the risk of maternal anemia, abortion and low birth weight. Approximately 85.3 million pregnancies occur annually in areas with Plasmodium falciparum transmission. Pregnancy has been reported to alter the pharmacokinetic properties of many anti-malarial drugs. Reduced drug exposure increases the risk of treatment failure. The objective of this study was to evaluate the population pharmacokinetic properties of artemether and its active metabolite dihydroartemisinin in pregnant women with uncomplicated P. falciparum malaria in Uganda.

Methods

Twenty-one women with uncomplicated P. falciparum malaria in the second and third trimesters of pregnancy received the fixed oral combination of 80 mg artemether and 480 mg lumefantrine twice daily for three days. Artemether and dihydroartemisinin plasma concentrations after the last dose administration were quantified using liquid chromatography coupled to tandem mass-spectroscopy. A simultaneous drug-metabolite population pharmacokinetic model for artemether and dihydroartemisinin was developed taking into account different disposition, absorption, error and covariate models. A separate modeling approach and a non-compartmental analysis (NCA) were also performed to enable a comparison with literature values and different modeling strategies.

Results

The treatment was well tolerated and there were no cases of recurrent malaria. A flexible absorption model with sequential zero-order and transit-compartment absorption followed by a simultaneous one-compartment disposition model for both artemether and dihydroartemisinin provided the best fit to the data. Artemether and dihydroartemisinin exposure was lower than that reported in non-pregnant populations. An approximately four-fold higher apparent volume of distribution for dihydroartemisinin was obtained by non-compartmental analysis and separate modeling compared to that from simultaneous modeling of the drug and metabolite. This highlights a potential pitfall when analyzing drug/metabolite data with traditional approaches.

Conclusion

The population pharmacokinetic properties of artemether and dihydroartemisinin, in pregnant women with uncomplicated P. falciparum malaria in Uganda, were described satisfactorily by a simultaneous drug-metabolite model without covariates. Concentrations of artemether and its metabolite dihydroartemisinin were relatively low in pregnancy compared to literature data. However, this should be interpreted with caution considered the limited literature available. Further studies in larger series are urgently needed for this vulnerable group.

Efavirenz pharmacokinetics during the third trimester of pregnancy and postpartum

BACKGROUND

The impact of pregnancy on efavirenz (EFV) pharmacokinetics is unknown.

METHODS

International Maternal Pediatric Adolescent AIDS Clinical Trials P1026s is an on-going, prospective, nonblinded study of antiretroviral pharmacokinetics in HIV-infected pregnant women that included a cohort receiving 600 mg EFV once daily as part of combination antiretroviral therapy. Intensive steady-state 24-hour blood sampling was performed during the third trimester and at 6-12 weeks postpartum. Maternal and umbilical cord blood samples were drawn at delivery. Pharmacokinetics targets were the estimated 10th percentile EFV area under the curve (AUC) in nonpregnant historical controls (40.0 mcg·hr(-1)·mL(-1)) and a trough concentration of 1 mcg/mL.

RESULTS

Twenty-five women were enrolled during the third trimester: median (range) age was 29.3 (18.9-42.9) years, weight 69.0 (40-130) kg, and gestational age 32.9 (30.1-38.7) weeks. Median (range) EFV AUC(0-24), C(max), and C(24 hours) were 55.4 mcg·hr(-1)·mL(-1) (13.5-220.3), 5.4 mcg/mL (1.9-12.2), and 1.6 mcg/mL (0.23-8.13), respectively. EFV AUC and C(max) did not differ during pregnancy and postpartum but C(24 hours) was lower during the third trimester (1.6 vs. 2.1 mcg/mL, P = 0.01). During the third trimester, 5 of 25 (20%) women had an EFV AUC below the target and 3 of 25 (12%) had a trough concentration below 1 mcg/mL. EFV cord blood/maternal concentration ratio was 0.49 (0.37-0.74). All women had a HIV-1 RNA viral load less than 400 copies per milliliter at delivery and 19 (76%) had a viral load below 50 copies per milliliter. One child was perinatally HIV infected. Three women were exposed to EFV throughout the first 6 weeks of pregnancy. EFV was well tolerated, and among the 25 infants, no congenital anomalies or newborn complications were reported.

CONCLUSIONS

Changes in EFV pharmacokinetics during pregnancy compared with postpartum are not sufficiently large enough to warrant a dose adjustment during pregnancy.

Environmental exposure to organophosphate pesticides: assessment of endocrine disruption and hepatotoxicity in pregnant women

In utero exposure is the first point of contact with environmental xenobiotics that may affect the maternal-placental-fetal balance. Considering that maternal pathophysiological changes affect intrauterine development, this pilot study was conducted to address how environmental exposure to organophosphate pesticides (OPs) during pregnancy may contribute to maternal endocrine disruption and disturbed hepatic function. A prospective study was carried out with pregnant women (n=97) living in a rural area of the Rio Negro province where OPs are intensively applied throughout 6 months of the year. Blood samples were obtained and biomarkers of OPs exposure (cholinesterases and β-glucuronidase), cortisol (CT) and progesterone (PG) levels, as well as glycemia, were determined. Parameters of liver injury were assayed by measuring aspartate aminotransferase (AST) and alanine aminotransferase (ALT); liver function was assayed by measuring albumin. Biomonitoring carried out during the pre-spraying period (PreS) and spraying period (SP) showed that the population studied was exposed to OPs, proven by the fact that plasma (PCh) and erythrocyte cholinesterase (AChE) decreased very significantly (p<0.01) during SP. CT values increased very significantly (p<0.01) in the first trimester of pregnancy during SP with respect to PreS. Individual values above the upper limit of the CT and PG reference range were found both in PreS and SP. This finding could be associated with changes in hormone metabolism pathways produced by OPs exposure. During the second trimester of pregnancy there were increases in ALT values and the AST/ALT ratio in SP, suggesting subclinical hepatotoxicity. In SP, glycemia was unchanged while albuminemia increased. Although anthropometric newborn parameters and pregnancy alterations were within normal values for the general population, the increase in CT in the maternal compartment may lead to impaired newborn health later in life.

The impact of drug metabolizing enzyme polymorphisms on outcomes after antenatal corticosteroid use

OBJECTIVE

To determine the impact of maternal and fetal single nucleotide polymorphisms in key betamethasone pathways on neonatal outcomes.

STUDY DESIGN

DNA was obtained from women given betamethasone and their infants. Samples were genotyped for 73 exploratory drug metabolism and glucocorticoid pathway single nucleotide polymorphisms. Clinical variables and neonatal outcomes were obtained. Logistic regression analysis using relevant clinical variables and genotypes to model for associations with neonatal respiratory distress syndrome was performed.

RESULTS

One hundred nine women delivering 117 infants were analyzed. Sixty-four infants (49%) developed respiratory distress syndrome. Multivariable analysis revealed that respiratory distress syndrome was associated with maternal single nucleotide polymorphisms in CYP3A5 (odds ratio [OR], 1.63; 95% confidence interval [CI], 1.16-2.30) and the glucocorticoid resistance (OR, 0.28; 95% CI, 0.08-0.95) and fetal single nucleotide polymorphisms in ADCY9 (OR, 0.17; 95% CI, 0.03-0.80) and CYP3A7*1E (rs28451617; OR, 23.68; 95% CI, 1.33-420.6).

CONCLUSION

Maternal and fetal genotypes are independently associated with neonatal respiratory distress syndrome after treatment with betamethasone for preterm labor.

Methadone: a review of drug-drug and pathophysiological interactions

Numerous established and potential drug interactions with methadone are clinically important in people treated with methadone either for addiction or for chronic pain. Methadone users often have comorbidities and are prescribed drugs that may interact with methadone. Methadone is extensively metabolized by cytochrome P450 (CYP) 3A4 and to a lesser extent by CYP 1A2, 2D6, 2D8, 2C9/2C8, 2C19, and 2B6. Eighty-six percent of methadone is protein bound, predominately to α1-acid glycoprotein (AGP). Polymorphisms in or interactions with CYPs that metabolize methadone, changes in protein binding, and other pathophysiological conditions affect the pharmacokinetic properties of methadone. It is critical for health care providers who treat patients on methadone to have adequate information on the interactions of methadone with other drugs of abuse and other medications. We set out to describe drug-drug interactions as well as physiological and pathophysiological factors that may impact the pharmacokinetics of methadone. Using MEDLINE, we conducted a systematic search for papers and related abstracts published between 1966 and June 2010. Keywords that included methadone, drug-drug interactions, CYP P450 and AGP identified a total of 7709 papers. Other databases, including the Cochrane Database of Systematic Reviews and Scopus, were also searched; an additional 929 papers were found. Final selection of 286 publications was based on the relevance of each paper to the topic. Over 50 such interactions were found. Interactions of methadone with other drugs can lead to increased or decreased methadone drug levels in patients and result in potential overdose or withdrawal, respectively. The former can contribute to methadone's fatality. Prescribers of methadone and pharmacists should enquire about any new medications (including natural products and over-the-counter medications) periodically, and especially when an otherwise stable patient suddenly experiences drug craving, withdrawal or intoxication.

Hcv coinfection, an important risk factor for hepatotoxicity in pregnant women starting antiretroviral therapy

OBJECTIVES

This retrospective cohort study evaluated the risk of hepatotoxicity in HIV-1 positive pregnant and non-pregnant women starting combined ART.

METHODS

Data were used from the ATHENA observational cohort. The study population consisted of HIV-1 infected, therapy naïve, pregnant and non-pregnant women, followed between January 1997 and February 2008. Demographic, treatment and pregnancy related data were collected. Risk of hepatotoxicity was determined using univariate and multivariate logistic regression. Analyses were adjusted for age, region of origin, baseline HIV-RNA levels and CD4 cell counts, cART regimen and hepatitis B and C coinfection. ALT and AST values of more than 5 times ULN were considered as hepatotoxicity.

RESULTS

Four-hundred and twenty-five pregnant and 1121 non-pregnant women were included. Independent risk factors of hepatotoxicity in all women were the presence of detectable HCV RNA (OR 5.48, 95% CI 2.25-13.38, p<0.001) and NVP use (OR 2.63, 95% CI 1.54-4.55, p<0.001). Stratified for pregnancy, the adjusted risk of hepatotoxicity was significantly associated with HCV coinfection only during pregnancy (OR 23.53, 95% CI 4.69-118.01, p<0.001). NVP use is related to hepatotoxicity in pregnant (OR 5.26, 95% CI 1.61-16.67, p<0.005) as well as in non-pregnant women (OR 2.13, 95% CI 1.11-4.00, p=0.02).

CONCLUSION

HCV coinfection and NVP use are associated with a higher risk of cART induced hepatotoxicity in pregnant women.

Maternal hepatic growth response to pregnancy in the mouse

Pregnancy is characterized by physiological adjustments in the maternal compartment. In this investigation, the influence of pregnancy on maternal liver was examined in CD-1 mice. Dramatic changes were observed in the size of the maternal liver during pregnancy. Livers doubled in weight from the non-pregnant state to day 18 of pregnancy. The pregnancy-induced hepatomegaly was a physiological event of liver growth confirmed by DNA content increase and detection of hepatocyte hyperplasia and hypertrophy. Growth of the liver was initiated following implantation and peaked at parturition. The expression and/or activities of key genes known to regulate liver regeneration, a phenomenon of liver growth compensatory to liver mass loss, were investigated. The results showed that pregnancy-dependent liver growth was associated with interleukin (IL)-6, tumor necrosis factor α, c-Jun and IL-1β, but independent of hepatocyte growth factor, fibroblast growth factor 1, tumor necrosis factor receptor 1, constitutive androstane receptor and pregnane X receptor. Furthermore, maternal liver growth was associated with the activation of hepatic signal transducer and activator of transcription 3, β-catenin and epidermal growth factor receptor, but pregnancy did not activate hepatic c-Met. The findings suggest that the molecular mechanisms regulating pregnancy-induced liver growth and injury-induced liver regeneration exhibit overlapping features but are not identical. In summary, the liver of the mouse adapts to the demands of pregnancy via a dramatic growth response driven by hepatocyte proliferation and size increase.

Buprenorphine for the treatment of perinatal opioid dependence: pharmacology and implications for antepartum, intrapartum, and postpartum care

Opioid dependence during pregnancy is associated with significant health risks for both the mother and her fetus. Opioid maintenance therapy with methadone (Dolophine) is the current standard of care, reduces medical and social risks associated with illicit drug use, and decreases rates of prematurity and low birth weight. However, treatment with methadone is frequently associated with neonatal abstinence syndrome. Buprenorphine is an alternative to methadone that preliminary data indicates is equivalent in safety and efficacy to methadone and significantly increases access to treatment. The pharmacology of buprenorphine and its implications for the care of pregnant women with opioid dependence are described.

Clinical therapeutics in pregnancy

Most drugs are not tested for use during pregnancy, consequently, labeling, which may include information about fetal safety, includes nothing about dosing, efficacy, or maternal safety. Yet these are concerns of health care providers considering treatment of disease during pregnancy. Therefore, the practitioner treats the pregnant woman with the same dose recommended for use in adults (typically men) or may decide not to treat the disease at all. However, is the choice of not treating a woman during pregnancy better than dealing with the challenges which accompany treatment? This paper, which summarizes metabolic and physiologic changes induced by pregnancy, illustrates that standard adult dosing is likely to be incorrect during pregnancy.

Mother-infant antidepressant concentrations, maternal depression, and perinatal events

OBJECTIVE

The authors explored the relationship of cord-maternal antidepressant concentration ratios and maternal depression with perinatal events and preterm birth.

METHOD

The investigators examined 21 mother-infant pairs that had antidepressant exposure during pregnancy. The antidepressants included serotonin reuptake inhibitors (SRIs) and nortriptyline (a norepinephrine inhibitor and mild SRI). The mothers were evaluated with the Structured Clinical Interview for DSM-IV. Depression ratings were repeated at 20, 30, and 36 weeks' pregnancy. At delivery, investigators assessed cord and maternal antidepressant concentrations, neonatal outcomes on the Peripartum Events Scale (PES), and gestational weeks at birth. The investigators performed this study at the Women's Behavioral HealthCARE Program, Western Psychiatric Institute and Clinic, University of Pittsburgh Medical Center, Pennsylvania, from April 2003 until September 2006.

RESULTS

Mean ± SD cord-to-maternal concentration ratios were 0.52 ± 0.35 (range, 0.00-1.64) for the parent drug and 0.54 ± 0.17 (range, 0.28-0.79) for the metabolite. Nine of 21 mothers (43%) had a major depressive episode. From examining the maximum depression ratings, the mean ± SD Structured Interview Guide for the Hamilton Depression Rating Scale, Atypical Depression Symptoms Version score was 16.0 ± 7.6. One third (7/21) of infants had at least 1 perinatal event (PES ≥ 1). The frequency of deliveries complicated by any perinatal event was similar in depressed and nondepressed mothers. There was no significant association between perinatal events and cord-to-maternal antidepressant concentration ratios or maternal depression levels. Exposure to short half-life antidepressants compared to fluoxetine resulted in more perinatal events (7/16 = 44% vs 0/5 = 0%; P = .06). Fourteen percent (3/21) of infants were preterm. Preterm birth was not associated with cord-to-maternal metabolite concentration ratios, depression levels, or exposure to fluoxetine.

CONCLUSIONS

Antidepressant-exposed infants experienced a limited number of transient perinatal events. No association between cord-maternal concentration ratios or maternal depression and perinatal events could be identified. Contrary to other reports, we detected no increased risk for perinatal events with fluoxetine therapy compared to the short half-life antidepressants.

TRIAL REGISTRATION

clinicaltrials.gov Identifier: NCT00279370.

Nuclear receptor-driven alterations in bile acid and lipid metabolic pathways during gestation

Nuclear receptor signalling is essential for physiological processes such as metabolism, development, and reproduction. Alterations in the endocrine state that naturally occur during pregnancy result in maternal adaptations to support the feto-placental unit. A series of studies have shown that nuclear receptor signalling is involved in maternal adaptations of bile acid, cholesterol, and lipid homeostasis pathways to ensure maintenance of the nutritional demands of the fetus. We discuss regulation of hepatic nuclear receptors and their target genes in pregnancy and their impact on the development of disorders such as intrahepatic cholestasis of pregnancy and oestrogen-induced hepatotoxicity. This article is part of a Special Issue entitled: Translating nuclear receptors from health to disease.

Pregnancy decreases rat CYP1A2 activity and expression

Pregnancy results in increased CYP3A- and CYP2D6-mediated clearance but decreases the clearance of CYP1A2 probe drugs. The aim of this study was to determine whether the decreased CYP1A2 activity during human pregnancy could be explained by decreased expression of CYP1A2 protein and mRNA using the rat as a model. Potential mechanisms leading to decreased CYP1A2 activity and expression were also investigated. Hepatic CYP1A2 activity, protein, and mRNA were measured during mid- and late gestation and compared to nonpregnant control levels. In addition, the effect of 17-β-estradiol and progesterone on CYP1A2 mRNA levels was assessed using rat hepatocytes, and the effect of estrogens or progesterone on CYP1A2 activity in vitro was tested. CYP1A2-mediated probe clearance decreased between 48 and 62% (p < 0.05) during pregnancy, with no difference in CYP1A2 activity between mid- and late pregnancy. This decrease in probe clearance was accompanied by a 33 ± 8% (midpregnancy) and 29 ± 27% (late pregnancy) decrease in CYP1A2 protein expression (p < 0.05) and a 53% decline in methoxyresorufin O-demethylation V(max) (p < 0.05). CYP1A2 mRNA was not significantly different from controls at midpregnancy and decreased by 27 ± 20% (p < 0.05) of control during late pregnancy. Estradiol and progesterone had no effect on CYP1A2 mRNA in rat hepatocytes and did not inhibit CYP1A2 activity. These data demonstrate that pregnancy decreases CYP1A2 activity and expression with a modest effect on CYP1A2 mRNA and suggest that the rat can be used as a model to study mechanisms by which pregnancy decreases CYP1A2 activity in humans.

Betamethasone in pregnancy: influence of maternal body weight and multiple gestation on pharmacokinetics

OBJECTIVE

The goals of the study were to estimate the pharmacokinetic parameters of standard dose betamethasone in a large obstetrics population and evaluate the effect of maternal body size and multiple gestation on the pharmacokinetic parameters and their observed variability.

STUDY DESIGN

This was a prospective pharmacokinetic study. Liquid chromatography mass spectrometry was used to measure betamethasone plasma concentrations. Pharmacokinetic parameters and significant clinical covariates were estimated with mixed effect modeling. Bootstrap analysis confirmed validity of the model.

RESULTS

Two hundred seventy-four blood samples from 77 patients were obtained. The greatest effect on pharmacokinetic variability was observed with maternal lean body weight (LBW). The relationship between the pharmacokinetic parameters and LBW remained linear over a wide range of maternal body sizes. Multiple gestations did not affect the pharmacokinetic parameters.

CONCLUSION

Individualization of betamethasone dosing by maternal LBW reduces variability in drug exposure. Mutiple gestations do not require betamethasone dosing adjustment, because pharmacokinetics are the same as singleton gestations.

Lopinavir tablet pharmacokinetics with an increased dose during pregnancy

OBJECTIVE

Reduced lopinavir concentrations have been demonstrated with use of the capsule formulation during the third trimester of pregnancy. This study determined lopinavir exposure with an increased dose of the new tablet formulation during the third trimester.

DESIGN

International Maternal Pediatric Adolescent AIDS Clinical Trials 1026s is a prospective nonblinded pharmacokinetic study in HIV-infected pregnant women, including a cohort receiving 2 lopinavir/ritonavir tablets (400 mg/100 mg) twice daily during the second trimester, 3 tablets (600 mg/150 mg) twice daily during the third trimester, and 2 tablets (400 mg/100 mg) twice daily post delivery through 2 weeks postpartum.

METHODS

Steady-state 12-hour pharmacokinetic profiles were performed during pregnancy and at 2 weeks postpartum. Lopinavir and ritonavir were measured by reverse-phase high-performance liquid chromatography (detection limit, 0.09 mcg/mL).

RESULTS

Thirty-three women were studied. Median lopinavir AUC for the second trimester (n = 11), third trimester (n = 33), and postpartum (n = 27) were 72, 96, and 133 mcg x hr/mL, respectively. Median minimum lopinavir concentrations were 3.4, 4.9, and 6.9 mcg/mL.

CONCLUSIONS

The higher lopinavir/ritonavir tablet dose (600 mg/150 mg) provided exposure during the third trimester similar to the average AUC (98 mcg x hr x mL(-1) in nonpregnant adults taking 400 mg/100 mg twice daily. The higher dose should be used during the second and third trimesters of pregnancy. Postpartum dosing can be reduced to standard dosing before 2 weeks postpartum.

Disposition of chiral and racemic fluoxetine and norfluoxetine across childbearing

OBJECTIVE

To add to the limited data on the clinical pharmacology of antidepressants during pregnancy, we examined the dose-corrected chiral and racemic levels (level/dose) of fluoxetine (FLX) and norfluoxetine (NorFLX) during pregnancy and early postpartum.

METHODS

The authors evaluated 17 pregnant women who received fluoxetine therapy. Doses were recorded weekly across gestation and postpartum. At 20, 30, and 36 weeks of gestation, during delivery, and 12 weeks after delivery, the depression level was assessed with the Hamilton Rating Scale for Depression (HRS-D), and plasma samples were analyzed for levels of S- and R-FLX and S- and R-NorFLX.

RESULTS

The mean ratios of the chiral parent drug (S-FLX + R-FLX) to metabolite levels (S-NorFLX + R-NorFLX) decreased across pregnancy. The differences were significant between 20-36 weeks and 30-36 weeks. After delivery, the mean dose-corrected level of the active moiety S-FLX and the mean ratio of the chiral parent drug (S-FLX + R-FLX) to metabolite level (S-NorFLX + R-NorFLX) significantly increased between delivery and 12 weeks postpartum. Most of the fluoxetine-treated subjects experienced remitted depressive episodes and euthymic mood levels during pregnancy and postpartum.

CONCLUSIONS

The findings extend earlier reports of increased antidepressant metabolism during pregnancy and refractory metabolism after delivery. These data may inform treatment decisions related to dosing in patients who receive fluoxetine during pregnancy.

Pharmacotherapy and pregnancy: highlights from the Second International Conference for Individualized Pharmacotherapy in Pregnancy

To address provider struggles to provide evidence-based, rational drug therapy to pregnant women, a second conference was convened to highlight the current research in the field. Speakers from academic centers and institutions spoke about: the unique physiology and pathology of pregnancy; pharmacokinetic changes in pregnancy; thyroid disorders in pregnancy; pharmacogenetics in pregnancy; the role of CYP2D6 in pregnancy; treating addiction in pregnancy; the power of teratology networks to inform clinical decisions; the use of anti-depressants in pregnancy; and how to utilize computer-based modeling to aid with individualized pharmacotherapy in pregnancy. The Conference highlighted several areas of collaboration with the current Obstetrics Pharmacology Research Units Network (OPRU) and hoped to stimulate further collaboration and knowledge in the area with the common goal to improve the ability to safely and effectively use individualized pharmacotherapy in pregnancy.

Gene profiling of maternal hepatic adaptations to pregnancy

BACKGROUND

Maternal metabolic demands change dramatically during the course of gestation and must be co-ordinated with the needs of the developing placenta and fetus. The liver is critically involved in metabolism and other important functions. However, maternal hepatic adjustments to pregnancy are poorly understood.

AIM

The aim of the study was to evaluate the influences of pregnancy on the maternal liver growth and gene expression profile.

METHODS

Holtzman Sprague-Dawley rats were mated and sacrificed at various stages of gestation and post-partum. The maternal livers were analysed in gravimetric response, DNA content by PicoGreen dsDNA quantitation reagent, hepatocyte ploidy by flow cytometry and hepatocyte proliferation by ki-67 immunostaining. Gene expression profiling of non-pregnant and gestation d18.5 maternal hepatic tissue was analysed using a DNA microarray approach and partially verified by northern blot or quantitative real-time PCR analysis.

RESULTS

During pregnancy, the liver exhibited approximately an 80% increase in size, proportional to the increase in body weight of the pregnant animals. The pregnancy-induced hepatomegaly was a physiological event of liver growth manifested by increases in maternal hepatic DNA content and hepatocyte proliferation. Pregnancy did not affect hepatocyte polyploidization. Pregnancy-dependent changes in hepatic expression were noted for a number of genes, including those associated with cell proliferation, cytokine signalling, liver regeneration and metabolism.

CONCLUSIONS

The metabolic demands of pregnancy cause marked adjustments in maternal liver physiology. Central to these adjustments are an expansion in hepatic capacity and changes in hepatic gene expression. Our findings provide insights into pregnancy-dependent hepatic adaptations.

Hypoglycemics: pharmacokinetic considerations during pregnancy

A wide range of physiological and hormonal changes occur during pregnancy. Most begin early in the first trimester and increase by the last trimester. These changes can significantly affect pharmacokinetics and pharmacodynamics of drugs and thus may alter their safety and efficacy. Approximately 5% of pregnant women are affected by some form of diabetes, with gestational diabetes being the most prevalent. Several classes of antidiabetic drugs are currently available for the treatment of diabetes, including human insulin, its short and long analogues, and oral hypoglycemic agents. Maternal and fetal responses to these drugs can be affected by changes in absorption, distribution, and elimination in both the mother and the placental-fetal unit. This can dictate the amount of drug that can cross and the amount that is metabolized or eliminated by the placenta. Further studies are needed on the safety of antidiabetic drugs in pregnancy to clarify the extent of their transplacental passage. Specifically, in vitro placental perfusion studies in combination with controlled trials and cord blood measurements can provide insight in to the pharmacokinetics of drug transport across the placenta. This article reviews common types of antidiabetic drugs, focusing on pharmacokinetic considerations that need to be incorporated into the decision on treatment in pregnancy.

Frequency of five important CYP2D6 alleles within an Iranian population (Eastern Azerbaijan)

Polymorphisms in cytochrome P450 genes encoding enzymes of critical importance for drug metabolism have the highest genetic influence on interindividual variations in drug bioavailability. Human CYP2D6 enzyme is claimed to be polymorphically expressed among different ethnic groups. It has been suggested to account for a large part of the interindividual differences in drug metabolism and pharmacokinetics. In the current investigation, 100 healthy unrelated subjects living in Tabriz, Iran, were randomly selected. Genotyping was designed to determine the frequencies of five major and important alleles: CYP2D6*2, CYP2D6*4, CYP2D6*5, CYP2D6*10, and CYP2D6*17. After collecting venous blood samples, polymerase chain reaction-restriction fragment length polymorphism methodology was performed for detection of the alleles (except CYP2D6*5, which has been detected using an allele-specific polymerase chain reaction procedure). Finally, the obtained data were used to determine the allele frequencies. The frequencies for CYP2D6 alleles *2, *4, *5, and *10 were 32%, 12.5%, 3%, and 9%, respectively. CYP2D6*17 was completely absent in this study group. Poor metabolizer phenotype can be related to *4/*4 and *4/*5 genotypes with a total frequency of 4%. This is the first study of the CYP2D6 genetic polymorphism in an Iranian population. The frequencies of the studied alleles resulted in degrees of differences between this population and Orientals, Saudi Arabians, and Caucasians, while similarities to the reported results obtained from the studies among Mediterraneans and South Indians are noticeable.

Update information on drug metabolism systems--2009, part II: summary of information on the effects of diseases and environmental factors on human cytochrome P450 (CYP) enzymes and transporters

The present paper is an update of the data on the effects of diseases and environmental factors on the expression and/or activity of human cytochrome P450 (CYP) enzymes and transporters. The data are presented in tabular form (Tables 1 and 2) and are a continuation of previously published summaries on the effects of drugs and other chemicals on CYP enzymes (Rendic, S.; Di Carlo, F. Drug Metab. Rev., 1997, 29(1-2), 413-580., Rendic, S. Drug Metab. Rev., 2002, 34(1-2), 83-448.). The collected information presented here is as stated by the cited author(s), and in cases when several references are cited the latest published information is included. Inconsistent results and conclusions obtained by different authors are highlighted, followed by discussion of the major findings. The searchable database is available as an Excel file, for information about file availability contact the corresponding author.

Lopinavir protein binding in HIV-1-infected pregnant women

BACKGROUND

Pregnancy may alter protein binding (PB) of highly bound protease inhibitors due to changes in plasma concentrations of albumin and alpha-1 acid glycoprotein (AAG). Small changes in PB can greatly impact the fraction of drug unbound (FU) exerting pharmacological effect. We report lopinavir (LPV) PB during third trimester (antepartum, AP) compared to > or =1.7 weeks postpartum (PP) to determine if FU changes compensate for reduced total concentrations reported previously.

METHODS

P1026s enrolled women receiving LPV/ritonavir, soft gel capsules 400/100 mg or 533/133 mg twice daily. LPV FU, albumin and AAG were determined AP and PP.

RESULTS

AP/PP samples were available from 29/25 women respectively with all but one woman receiving the same dose AP/PP. LPV FU was increased 18% AP vs. PP (mean 0.96+/-0.16% AP vs. 0.82+/-0.21% PP, P=0.001). Mean protein concentrations were reduced AP (AAG=477 mg/L; albumin=3.28 mg/dL) vs. PP (AAG=1007 mg/L; albumin=3.85 mg/dL) (P<0.0001 for each comparison). AAG concentration correlated with LPV binding. Total LPV concentration did not correlate with LPV FU AP or PP. However, higher LPV concentration PP was associated with reduced PB and higher FU after adjustment for AAG.

CONCLUSIONS

LPV FU was higher and AAG lower AP vs. PP. The 18% increase in LPV FU AP is smaller than the reduction in total LPV concentration reported previously and is not of sufficient magnitude to eliminate the need for an increased dose during pregnancy.