Maternal-fetal transport of hypoglycaemic drugs

Efficacy and safety of metformin during pregnancy: an update

During the last decades, gestational diabetes mellitus (GDM) prevalence has been on the rise. While insulin remains the gold standard treatment for GDM, metformin use during pregnancy is controversial. This review aimed to comprehensively assess the available data on the efficacy and safety of metformin during pregnancy, both for the mother and the offspring. Metformin has been validated for maternal efficacy and safety, achieving comparable glycemic control with insulin. Additionally, it reduces maternal weight gain and possibly the occurrence of hypertensive disorders. During the early neonatal period, metformin administration does not increase the risk of congenital anomalies or other major adverse effects, including lower APGAR score at 5 min, neonatal intensive care unit admissions, and respiratory distress syndrome. Several studies have demonstrated a reduction in neonatal hypoglycemia. Metformin has been associated with an increase in preterm births and lower birth weight, although this effect is controversial and depends on the indication for which it was administered. Evidence indicates possible altered fetal programming and predisposition to childhood obesity and metabolic syndrome during adulthood after use of metformin in pregnancy. With critical questions still requiring a final verdict, ongoing research on the field must be conducted.

In vivo pharmacokinetic analyses of placental transfer of three drugs of different physicochemical properties in pregnant rats

Although the use of medication during pregnancy is common, information on exposure to the developing fetus and potential teratogenic effects is often lacking. This study used a rat model to examine the placental transfer of three small-molecule drugs with molecular weights ranging from approximately 300 to 800 Da with different physicochemical properties. Time-mated Sprague Dawley (Hsd:SD) rats aged 11-13 weeks were administered either glyburide, rifaximin, or fentanyl at gestational day 15. Maternal blood, placentae, and fetuses were collected at 5 min, 30 min, 1 h, 4 h, 8 h, 24 h, 48 h, and 96 h post-dose. To characterize the rate and extent of placental drug transfer, we calculated several pharmacokinetic parameters such as maximum concentration (Cmax), time to maximum concentration (Tmax), area under the concentration-time curve (AUC), half-life (t_1/2), clearance (CL), and volume of distribution (Vd) for plasma, placenta, and fetus tissues. The results indicated showed that fetal exposure was lowest for glyburide, accounting for only 2.2 % of maternal plasma exposure as measured by their corresponding AUC ratio, followed by rifaximin (37.9 %) and fentanyl (172.4 %). The fetus/placenta AUC ratios were found to be 10.7 % for glyburide, 11.8 % for rifaximin, and 39.1 % for fentanyl. These findings suggest that although the placenta acts as a protective shield for the fetus, the extent of protection varies for different drugs and depends on factors such as molecular weight, lipid solubility, transporter-mediated efflux, and binding to maternal and fetal plasma proteins.

Disruption of Fetal Eye Development Caused by Insulin-induced Maternal Hypoglycemia in Rats

We previously revealed that insulin-induced severe and long-lasting maternal hypoglycemia in rats caused anophthalmia and microphthalmia in fetuses; however, it remained unclear whether hypoglycemia-induced eye anomalies were developmental retardation or disruption, and when and how they developed. Hence, we induced hypoglycemia in pregnant Sprague-Dawley rats by injecting insulin from Days 6 to 11 of pregnancy and performed periodical histopathological examination of fetal eyes from embryonic days (E)10 to 20. On E10, optic vesicle had developed normally both in the control and insulin-treated group; however, on E11, optic cup (OC) had developed in the control group but not in the insulin-treated group. On E12, neural retina (NR), retinal pigmented epithelium (RPE), lens, and presumptive cornea had been observed in the control group. In contrast, lens pit and OC with remaining space between RPE and NR had developed in the insulin-treated group. From E13 to E15, developmental disruption characterized by defects, hypoplasia, and degeneration in the retina, lens, and cornea was observed in the insulin-treated group, resulting in anophthalmia or microphthalmia on E20. Moreover, the expression of MITF and chx10, which are essential for early eye development by expressing in the presumptive retina and lens and regulating each other's expression level, was ectopic and suppressed on E11. In conclusion, insulin-induced maternal hypoglycemia caused developmental disruption, but not simple developmental retardation of fetal eyes, and its trigger might be a failure of presumptive retina and lens to interact on E11.

Effects of glucokinase activator, DS-7309, on embryo-fetal developmental toxicity in rats and rabbits

The toxicological effects of DS-7309, a glucokinase activator, on pregnancy and embryo-fetal development in rats and rabbits and maternal blood glucose levels were examined. DS-7309 was administered at 3, 10, or 100 mg/kg to rats from Days 7-17 of pregnancy or at 10, 30, or 100 mg/kg to rabbits from Days 6-18 of pregnancy. In rats, maternal hypoglycemia (approximately 50 mg/dL) was seen at 3 and 10 mg/kg, but it recovered 7 h after dosing, leading to no toxic changes. In contrast, continuous severe maternal hypoglycemia (approximately 40 mg/dL, ≥7 h), fetal eye anomalies, and decreased fetal body weight were noted at 100 mg/kg. In rabbits, no fetal anomalies were seen at 10 and 30 mg/kg where maternal blood glucose level dropped to approximately 60-90 mg/dL, but recovered by 7 h after dosing at the latest. In contrast, at 100 mg/kg, severe hypoglycemia (around 60 mg/dL) was maintained and did not recover until 24 h after dosing; it resulted in decreased fetal viability and increased fetal skeleton anomalies. These findings indicate that DS-7309 could lead to embryo-fetal toxicity in rats and rabbits, with such toxicity considered to be related to continuous severe maternal hypoglycemia.

Comparative effects of glibenclamide, metformin and insulin on fetal pancreatic histology and maternal blood glucose in pregnant streptozotocin-induced diabetic rats

BACKGROUND

Oral hypoglycemic agents use during pregnancy was assumed to cause fetal macrosomia and skeletal deformities, and maternal complications due to significant transfer across placenta or ineffective control of blood glucose.

OBJECTIVE

This study investigated effects of insulin, metformin and glibenclamide on maternal blood glucose; and fetal crown-rump length, gross malformation and pancreatic histology in pregnant streptozotocin-induced diabetic rats.

METHODS

Twenty-five pregnant rats of groups 1 to 5 as normal and diabetic controls; and diabetic treated with insulin, metformin and glibenclamide were used. Experimental GDM was induced using 45 and 35mg/Kgbw of intraperitoneal streptozotocin.

RESULTS

Metformin, Insulin and Glibenclamide significantly reduced maternal glucose by 140.6mg/dL, 103.2mg/dL and 98.54mg/dl; respectively and showed islets with regular interlobular ducts, islets with some irregular interlobular ducts, and islets with many irregular interlobular ducts in histological fetal pancreatic photomicrographs respectively. This depicts metformin having highest ameliorative effect. There were no significant differences in maternal and fetal body weights, maternal blood glucose between diabetic groups, and fetal gross examination.

CONCLUSION

At the doses used in this research, metformin and glibenclamide showed no adverse effects on maternal and fetal features in the treatment of GDM. Thus, they can be used as safe and inexpensive alternatives to insulin.

Management of sulfonylurea-treated monogenic diabetes in pregnancy: implications of placental glibenclamide transfer

The optimum treatment for HNF1A/HNF4A maturity-onset diabetes of the young and ATP-sensitive potassium (K_ATP ) channel neonatal diabetes, outside pregnancy, is sulfonylureas, but there is little evidence regarding the most appropriate treatment during pregnancy. Glibenclamide has been widely used in the treatment of gestational diabetes, but recent data have established that glibenclamide crosses the placenta and increases risk of macrosomia and neonatal hypoglycaemia. This raises questions about its use in pregnancy. We review the available evidence and make recommendations for the management of monogenic diabetes in pregnancy. Due to the risk of stimulating increased insulin secretion in utero, we recommend that in women with HNF1A/ HNF4A maturity-onset diabetes of the young, those with good glycaemic control who are on a sulfonylurea per conception either transfer to insulin before conception (at the risk of a short-term deterioration of glycaemic control) or continue with sulfonylurea (glibenclamide) treatment in the first trimester and transfer to insulin in the second trimester. Early delivery is needed if the fetus inherits an HNF4A mutation from either parent because increased insulin secretion results in ~800-g weight gain in utero, and prolonged severe neonatal hypoglycaemia can occur post-delivery. If the fetus inherits a K_ATP neonatal diabetes mutation from their mother they have greatly reduced insulin secretion in utero that reduces fetal growth by ~900 g. Treating the mother with glibenclamide in the third trimester treats the affected fetus in utero, normalising fetal growth, but is not desirable, especially in the high doses used in this condition, if the fetus is unaffected. Prospective studies of pregnancy in monogenic diabetes are needed.

Effects of maternal hypoglycemia on fetal eye and skeleton development in rats

The relationship between insulin-induced maternal hypoglycemia and teratogenicity was investigated in detail. We injected 4 different forms of insulin (insulin human, aspart, glargine, and detemir) subcutaneously at 1 or 2 dose levels to Sprague-Dawley rats from Days 6 to 11 of pregnancy, measured blood glucose levels, and conducted fetal examination. In the insulin human and aspart (low dose) groups, while severe hypoglycemia (approximately 50mg/dL) was seen, it lasted only 6h and no fetal anomalies were observed. Fetal axial skeleton anomalies were observed in the aspart (high dose) group, which exhibited intermediate-duration of severe hypoglycemia (9h). Eye and axial skeleton anomalies were observed in the glargine and detemir groups, which exhibited continuous severe hypoglycemia (≥9h). These results revealed that insulin-induced maternal hypoglycemia caused fetal eye and skeleton anomalies and the causative key factors were duration of maternal severe hypoglycemia.

Chemotherapy against cancer during pregnancy: A systematic review on neonatal outcomes

BACKGROUND

The concomitant incidence of cancer and pregnancy has increased in recent years because of the increase in maternal age at the time of the 1st pregnancy. The diagnosis of cancer in a pregnant woman causes ethical and therapeutic problems for both the patient and the physician. The main aim of this paper is to describe the available evidence concerning the short- and long-term neonatal impact of chemotherapy given to pregnant women.

METHODS

The relevant publications in English were identified by a systematic review of MEDLINE and PubMed for the last 15 years. The search strategy included "cancer[Title/Abstract] OR tumor[Title/Abstract] AND pregnancy[Title/Abstract] OR pregnant[Title/Abstract] AND embryo[Title/Abstract] or fetus[Title/Abstract] or neonate[Title/Abstract] or newborn[Title/Abstract] or pediatric[Title/Abstract] or child[Title/Abstract] AND English[lang]."

RESULTS

An analysis of the literature showed that only the administration of chemotherapy during the embryonic stage of conceptus is dangerous and can lead to the termination of the pregnancy. When the disease is diagnosed in the 2nd or 3rd trimester of gestation or when it is possible to delay the initiation of chemotherapy beyond the 14th week, the risk of severe problems for the fetus are low, and pregnancy termination is not required.

CONCLUSION

Data regarding the final outcome of children who have received in utero chemotherapy seem reassuring. Only the administration in the embryonal stage of conceptus is dangerous and can lead to the termination of pregnancy. When the disease is diagnosed in the 2nd or 3rd trimester of gestation or when it is possible to delay the initiation of chemotherapy beyond the 14th week, the risk of severe problems for the fetus are low and pregnancy termination is not needed. Increased knowledge of how to minimize the risks of chemotherapy can reduce improper management including unnecessary termination of pregnancy, delayed maternal treatment, and iatrogenic preterm delivery.

Treating diabetes during pregnancy

INTRODUCTION

Gestational diabetes mellitus (GDM), defined as glucose intolerance with first recognition or onset during pregnancy, is steadily rising in prevalence. GDM affects ∼ 3 - 5% of pregnancies in the US and is associated with significant adverse perinatal and maternal outcomes. Diagnosing and treating GDM early in pregnancy is of utmost importance as it can prevent poor outcomes such as macrosomia, shoulder dystocia and obstetric complications.

AREAS COVERED

This review describes the importance of treating GDM and the various available interventions for glycemic control in women with GDM, including the latest evidence regarding pharmacological treatments and specifically anti-hyperglycemic agents. It deals with timing of pharmacological treatments, recommended doses and what pharmacological agent should be used.

EXPERT OPINION

Unless diagnosed late during pregnancy, a stepwise approach is the best way to treat GDM, beginning with diet and exercise and proceeding to pharmacological interventions if failure occurred. Although insulin is the dominant treatment, the use of anti-hyperglycemic agents such as glyburide and metformin in treating GDM has gained popularity and consideration should be made using these agents as first-line pharmacological treatment. Anti-hyperglycemic agents do not require frequent monitoring or injections and may therefore appeal more to patients. Further studies are needed regarding long-acting insulin and other anti-hyperglycemic agents such as thiazolidinediones, as well as identifying treatment options more specific to an individual based on risk factors and other variables predicting treatment outcomes in GDM.

Early-life glucocorticoid exposure: the hypothalamic-pituitary-adrenal axis, placental function, and long-term disease risk

An adverse early-life environment is associated with long-term disease consequences. Adversity early in life is hypothesized to elicit developmental adaptations that serve to improve fetal and postnatal survival and prepare the organism for a particular range of postnatal environments. These processes, although adaptive in their nature, may later prove to be maladaptive or disadvantageous if the prenatal and postnatal environments are widely discrepant. The exposure of the fetus to elevated levels of either endogenous or synthetic glucocorticoids is one model of early-life adversity that contributes substantially to the propensity of developing disease. Moreover, early-life glucocorticoid exposure has direct clinical relevance because synthetic glucocorticoids are routinely used in the management of women at risk of early preterm birth. In this regard, reports of adverse events in human newborns have raised concerns about the safety of glucocorticoid treatment; synthetic glucocorticoids have detrimental effects on fetal growth and development, childhood cognition, and long-term behavioral outcomes. Experimental evidence supports a link between prenatal exposure to synthetic glucocorticoids and alterations in fetal development and changes in placental function, and many of these alterations appear to be permanent. Because the placenta is the conduit between the maternal and fetal environments, it is likely that placental function plays a key role in mediating effects of fetal glucocorticoid exposure on hypothalamic-pituitary-adrenal axis development and long-term disease risk. Here we review recent insights into how the placenta responds to changes in the intrauterine glucocorticoid environment and discuss possible mechanisms by which the placenta mediates fetal hypothalamic-pituitary-adrenal development, metabolism, cardiovascular function, and reproduction.

Oral Hypoglycemic Agents in pregnancy: An Update

INTRODUCTION

Traditionally, insulin has been the gold standard in the management of Type 2 diabetes in pregnancy and gestational diabetes. However, insulin therapy can be inconvenient because of the needs for multiple injections, its associated cost, pain at the injection site, need for refrigeration, and skillful handling of the syringes. This has led to the exploration of oral hypoglycemic agents as an alternative to insulin therapy.

OBJECTIVES

This review examines and evaluates the evidences on the efficacy, safety, and current recommendations of oral hypoglycemic agents.

CONCLUSION

The evidence of this study supports the use of glyburide and metformin in the management of Type 2 diabetes and gestational diabetes with no increased risk of neonatal hypoglycemia or congenital anomalies. The safety of these oral hypoglycemic agents are limited to the prenatal period and more randomized controlled trials are required to provide information on the long-term follow up on neonatal and cognitive development.

Gestational diabetes mellitus: Non-insulin management

Gestational diabetes mellitus (GDM) complicates a substantial number of pregnancies. There is consensus that in patients of GDM, excellent blood glucose control, with diet and, when necessary, oral hypoglycemics and insulin results in improved perinatal outcomes, and appreciably reduces the probability of serious neonatal morbidity compared with routine prenatal care. Goals of metabolic management of a pregnancy complicated with GDM have to balance the needs of a healthy pregnancy with the requirements to control glucose level. Medical nutrition therapy is the cornerstone of therapy for women with GDM. Surveillance with daily self-monitoring of blood glucose has been found to help guide management in a much better way than blood glucose checking in labs and clinics, which tends to be less frequent. Historically, insulin has been the therapeutic agent of choice for controlling hyperglycemia in pregnant women. However, difficulty in medication administration with multiple daily injections, potential for hypoglycemia, and increase in appetite and weight make this therapeutic option cumbersome for many pregnant patients. Use of oral hypogycemic agents (OHAs) in pregnancy has opened new vistas for GDM management. At present, there is a growing acceptance of glyburide (glibenclamide) use as the primary therapy for GDM. Glyburide and metformin have been found to be safe, effective and economical for the treatment of gestational diabetes. Insulin, however, still has an important role to play in GDM. GDM is a window of opportunity, which needs to be seized, for prevention of diabetes in future life. Goal of our educational programs should be not only to improve pregnancy outcomes but also to promote healthy lifestyle changes for the mother that will last long after delivery. Team effort on part of obstetricians and endocrinologists is required to make "the diabetes capital of the world" into "the diabetes care capital of the world".

Decreased urine albumin:creatinine ratios in infants of diabetic mothers: does exposure to diabetic pregnancies alter fetal renal development?

Offspring of diabetic mothers experience an increased risk for type 2 diabetes but it is not known whether diabetic pregnancies also confer a higher inter-generational risk for diabetic complications. Because microalbuminuria is a sensitive indicator of glomerular damage, we compared the urine albumin:creatinine ratios (ACRs) between 65 infants of diabetic mothers (InfDM+) and 59 infants of non-diabetic mothers (InfDM−), and repeated the comparisons in 21 InfDM+ and 19 InfDM− when children were 5–19 months old. ACRs were higher among neonates compared with normal reference values for adults, but declined with increasing age. The only independent predictor of higher ACRs in a logistic regression model (⩾13 mg/mmol v. <13 mg/mmol) was the presence of delivery complications (odds ratio 2.95; P = 0.015). Neither high nor low birth weight was associated with higher neonatal ACRs. The most unique finding of the study was that InfDM+ had significantly lower ACRs than InfDM− [mean = 12.9 (median = 6.0) v. mean = 16.6 (median = 11.5), respectively at P = 0.05] even after adjusting for other variables using logistic regression (odds ratio 0.25; P = 0.001). In contrast, by 5–19 months, there was a trend toward higher ACRs among InfDM+ compared with InfDM− [mean = 6.3 mg/mmol (median = 1.9) v. mean = 3.0 mg/mmol (median = 2.5), respectively at P = 0.25]. Lower ACRs in InfDM+ may be due to developmental changes in fetal kidneys induced by hyperinsulinemia. Although the implications of this observation are unclear, it is possible that exposure to a diabetic intrauterine environment might influence the later risk for renal disease.

Fetal hypothalamic neuroprogenitor cell culture: preferential differentiation paths induced by leptin and insulin

In response to temporally orchestrated growth factor stimulation, developing neural stem/progenitor cells undergo extensive self-renewal and then generate neurons and astrocytes. Fetal neonatal leptin and insulin deficiency results in reduced hypothalamic axonal pathways regulating appetite, which may predispose to offspring hyperphagia and obesity. Neural development of the arcuate nucleus, a key target of adiposity signals, leptin and insulin, is immature at birth. Hence, to explore proximate effects of leptin/insulin on hypothalamic development, we determined trophic and differentiation effects on neural stem/progenitor cells using a model of fetal hypothalamic neurospheres (NS). NS cultures were produced from embryonic d 20 fetal rats and passage 1 and passage 2 cells examined for proliferation and differentiation into neurons (neuronal nuclei, class IIIβ-tubulin, and doublecortin) and astrocytes (glial fibrillary acidic protein). Leptin-induced NS proliferation was significantly greater than that induced by insulin, although both effects were blocked by Notch, extracellular signal-regulated kinase, or signal transducer and activator of transcription 3 inhibition. Leptin preferentially induced neuronal, whereas insulin promoted astrocyte differentiation. Extracellular signal-regulated kinase inhibition suppressed both leptin and insulin-mediated differentiation, whereas signal transducer and activator of transcription inhibition only affected leptin-mediated responses. These findings demonstrate preferential and disparate differentiation paths induced by leptin and insulin. Altered fetal exposure to leptin or insulin, resulting from fetal growth restriction, macrosomia, or maternal diabetes, may potentially have marked effects on fetal brain development.

Treatment of gestational diabetes mellitus: glyburide compared to subcutaneous insulin therapy and associated perinatal outcomes

OBJECTIVE

To examine perinatal outcomes in women with gestational diabetes mellitus treated with glyburide compared to insulin injections.

STUDY DESIGN

This is a retrospective cohort study of women diagnosed with gestational diabetes mellitus (GDM) who required pharmaceutical therapy and were enrolled in the Sweet Success California Diabetes and Pregnancy Program between 2001 and 2004, a California state-wide program. Women managed with glyburide were compared to women treated with insulin injections. Perinatal outcomes were compared using chi-square test and multivariable logistic regression models; statistical significance was indicated by p < 0.05 and 95% confidence intervals (CI).

RESULTS

Among the 10,682 women with GDM who required medical therapy and met study criteria, 2073 (19.4%) received glyburide and 8609 (80.6%) received subcutaneous insulin injections. Compared to insulin therapy and controlling for confounders, oral hypoglycemic treatment was associated with increased risk of birthweight >4000 g (aOR = 1.29; 95% CI [1.03-1.64]), and admission to the intensive care nursery (aOR = 1.46 [1.07-2.00]).

CONCLUSION

Neonates born to women with gestational diabetes managed on glyburide, and were more likely to be macrosomic and to be admitted to the intensive care unit compared to those treated with insulin injections. These findings should be examined in a large, prospective trial.

The first case report of sulfonylurea use in a woman with permanent neonatal diabetes mellitus due to KCNJ11 mutation during a high-risk pregnancy

Sulfonylureas (SUs) were proven to be more effective than insulin in most Kir6.2 permanent neonatal diabetes mellitus (PNDM) patients. We report SU use during pregnancy in PNDM. A woman with the R201H Kir6.2 mutation became pregnant at the age of 37. The patient had been on glipizide 30 mg for 3 yr; her glycosylated hemoglobin level was 5.8%. She was diagnosed with chronic diabetes complications and a congenital defect of the urogenitary tract-a bicornuate uterus with septum. Because the effect of SU on fetal development is uncertain, she was switched to insulin after the pregnancy diagnosis; however, the subsequent glycemic control was unsatisfactory, with episodes of hyper- and hypoglycemia. Thus, in the second trimester, the patient was transferred to SU (glibenclamide, 40 mg), which resulted in stabilization of glycemic control; glycosylated hemoglobin in the third trimester was 5.8%. Prenatal genetic testing excluded the Kir6.2 R201H mutation in the fetus. A preterm cesarean delivery was carried out in the 35th week. The Apgar score of the newborn boy (weight, 3010 g; 75th percentile) was 8 at 1 min. He presented with hypoglycemia, transient tachypnea of the newborn, and hyperbilirubinemia. The recovery was uneventful. No birth defects were recorded. His development at the ninth month of life was normal. In summary, we show a high-risk pregnancy in long-term PNDM that despite perinatal complications ended with the birth of a healthy child. SUs, which seem to constitute an alternative to insulin during pregnancy in Kir6.2-related PNDM, were used during the conception period and most of the second and third trimesters.

Metformin compared with glyburide for the management of gestational diabetes

OBJECTIVE

To assess blood glucose control and neonatal outcomes when women with gestational diabetes mellitus (GDM) were treated with metformin or glyburide.

METHODS

When an appropriate diet was insufficient to control their blood glucose levels, women with GDM were randomized to a glyburide or a metformin treatment group. If the maximum dose was reached, the assessed drug was replaced by insulin. The primary outcome measures analyzed were maternal glucose levels during pregnancy, birth weight, and neonatal glucose levels.

RESULTS

The only significant difference in outcome between the 2 treatment drugs was that maternal weight gain during pregnancy was less in the metformin (n=40) than in the glyburide group (n=32) (10.3 kg vs 7.6 kg; P=0.02). No differences were found in treatment failure, mean level of fasting or postprandial plasma glucose, rate of participants with glycated hemoglobin, birth weight, rate of large-for-gestational-age newborns, or newborns with hypoglycemia.

CONCLUSION

The treatment of GDM with metformin or glyburide was found to be equivalent for both women and newborns.

Obesity and gestational diabetes

The prevalence of both obesity and gestational diabetes mellitus (GDM) is increasing worldwide. GDM affects about 7% of all pregnancies and is defined as any degree of impaired glucose tolerance during gestation. The presence of obesity has a significant impact on both maternal and fetal complications associated with GDM. These complications can be addressed, at least in part, by good glycaemic control during pregnancy. The significance and impact of obesity in women with GDM are discussed in this article, together with treatment options, the need for long-term risk modification and postpartum follow-up.

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.

Gestational diabetes: diagnosis and management

PURPOSE

To review the diagnosis and management of gestational diabetes.

EPIDEMIOLOGY

In the United States, approximately 2 to 5% of all pregnant women have gestational diabetes. Those women with a family history of type 2 diabetes mellitus, Asian or native American race, Latina ethnicity or obesity are at higher risk for developing gestational diabetes.

CONCLUSION

Women with gestational diabetes who are treated appropriately can achieve good outcomes in the majority of pregnancies. Frequent blood glucose monitoring, nutrition counseling and frequent physician contact allow for individualized care to achieve optimal outcomes. Such treatment includes diet, exercise and insulin. The use of oral hypoglycemic agents is controversial and there is some concern about worse maternal and neonatal outcomes as compared to treatment with insulin. Evolving technologies promise to provide more therapeutic options.

Probiotic Pre-treatment Reduces Gliclazide Permeation (ex vivo) in Healthy Rats but Increases It in Diabetic Rats to the Level Seen in Untreated Healthy Rats

Aim

To investigate the influence of probiotic pre-treatment on the permeation of the antidiabetic drug gliclazide in healthy and diabetic rats.

Methods

Wistar rats (age 2–3 months, weight 350 ± 50 g) were randomly allocated into one of 4 groups (N = 16 each group): healthy control, healthy probiotic, diabetic control, and diabetic probiotic. Probiotics (75 mg/kg, equal quantities of Lactobacillus acidophilus, Bifidobacterium lactis, and Lactobacillus rhamnosus) were administered twice a day for three days to the appropriate groups after diabetes had been induced with alloxan i.v. 30 mg/kg. Rats were sacrificed, ileal tissues mounted in Ussing chambers and gliclazide (200 µg/mL) was administered for the measurement of the mucosal to serosal absorption Jss^(MtoS) and serosal to mucosal secretion Jss^(StoM) of gliclazide.

Results

Treatment of healthy rats with probiotics reduced Jss^(MtoS) of gliclazide from 1.2 ± 0.3 to 0.3 ± 0.1 µg/min/cm² (P < 0.01) and increased Jss^(StoM)from 0.6 ± 0.1 to 1.4 ± 0.3 (P < 0.01) resulting in net secretion while, in diabetic tissues, treatment with probiotics increased both Jss^(MtoS) and Jss^(StoM)fluxes of gliclazide to the comparable levels of healthy tissues resulting in net absorption.

Discussion

In healthy rats, the reduction in Jss^(MtoS) after probiotics administration could be explained by the production of bacterial metabolites that upregulate the mucosal efflux drug transporters Mrp2 that control gliclazide transport. In diabetic rats, the restored fluxes of gliclazide after probiotic treatment, suggests the normalization of the functionality of the drug transporters resulting in a net absorption.

Conclusion

Probiotics may alter gliclazide transport across rat ileal tissue studied ex vivo.

Glyburide for the treatment of gestational diabetes. A critical appraisal

The clinical experience with glyburide treatment of GDM has moved ahead of the science. A single randomized controlled trial of glyburide versus insulin indicates that glyburide treatment can provide a relatively safe alternative to insulin therapy. Subsequent retrospective trials have shown that up to 20% of GDM patients, especially those with substantial pretreatment hyperglycemia, are likely to require adjunctive or alternative therapy with insulin. These follow-on trials have also demonstrated that glyburide treatment, compared with insulin, actually results in lower mean glucose values and a higher percentage of "excellent glycemic control" with fewer hypoglycemic episodes. With the emerging view that glyburide treatment compared with insulin improves glycemic profiles, it should be expected to reduce the frequency of newborn obesity. Larger randomized controlled trials are necessary to clarify this question and the concerns regarding neonatal metabolic morbidity in glyburide-treated offspring.

A 10-year retrospective analysis of pregnancy outcome in pregestational Type 2 diabetes: comparison of insulin and oral glucose-lowering agents

AIMS

To review the use of oral glucose-lowering agents (OGLA) in pregnant women with Type 2 diabetes mellitus.

METHODS

Retrospective analysis of outcomes and their predictors in singleton pregnancies > or = 24 weeks managed at Groote Schuur hospital, Cape Town, South Africa from 1991 to 2000. There were 379 pregnancies, subdivided into three groups according to therapy: OGLA alone, converted from OGLA to insulin, insulin alone or converted from diet alone to insulin. The OGLA used were metformin and glibenclamide.

RESULTS

Mean glycated haemoglobin (HbA(1c)) was similar at booking and throughout pregnancy in all groups. In the OGLA alone, converted from OGLA to insulin and insulin alone/converted from diet alone to insulin groups, fetal anomaly rates were comparable: 5.7%, 2.0% and 0.0%, P = 0.2, respectively; whereas perinatal mortality rates (per 1000 births) were: 125, 28, 33, P = 0.003, respectively. Booking HbA(1c) was independently associated with fetal anomaly [odds ratio (OR) 1.48; 95% confidence interval (CI) 1.11, 1.97; P = 0.006]. The specific OGLA used in the first trimester was not associated with the occurrence of fetal anomaly. Last HbA(1c) (OR 1.65; 95% CI 1.16, 2.42; P = 0.005) and fetal anomaly (OR 15.18; 95% CI 2.43, 93.37; P = 0.005) were independently associated with perinatal mortality. Conversion from OGLA to insulin was protective for perinatal mortality compared with OGLA alone treatment (OR 0.220; 95% CI 0.061, 0.756; P = 0.024). No perinatal mortality was observed in women on metformin alone.

CONCLUSIONS

These data suggest that metformin and glibenclamide are not teratogenic but that it is advisable to replace OGLA, in particular glibenclamide, with insulin when women book for pregnancy care to reduce perinatal mortality rates.

Structure-based modelling in reproductive toxicology: (Q)SARs for the placental barrier

The replacement of animal testing for endpoints such as reproductive toxicity is a long-term goal. This study describes the possibilities of using simple (quantitative) structure-activity relationships ((Q)SARs) to predict whether a molecule may cross the placental membrane. The concept is straightforward, if a molecule is not able to cross the placental barrier, then it will not be a reproductive toxicant. Such a model could be placed at the start of any integrated testing strategy. To develop these models the literature was reviewed to obtain data relating to the transfer of molecules across the placenta. A reasonable number of data were obtained and are suitable for the modelling of the ability of a molecule to cross the placenta. Clearance or transfer indices data were sought due to their ability to eliminate inter-placental variation by standardising drug clearance to the reference compound antipyrine. Modelling of the permeability data indicates that (Q)SARs with reasonable statistical fit can be developed for the ability of molecules to cross the placental barrier membrane. Analysis of the models indicates that molecular size, hydrophobicity and hydrogen-bonding ability are molecular properties that may govern the ability of a molecule to cross the placental barrier.

P-glycoprotein in the placenta: Expression, localization, regulation and function

Detailed understanding of the mechanisms employed in transfer of drugs across the placenta is essential for optimization of pharmacotherapy during pregnancy. Disclosure of drug efflux transporters as an "active component" of the placental barrier has brought new important insights into the field of transplacental pharmacokinetics. P-glycoprotein (P-gp, MDR1) is the first discovered and so far the best characterized of drug efflux transporters, whose role in the regulation of drug disposition to the fetus has been extensively studied. Expression of P-gp in the placental trophoblast layer was confirmed at the mRNA and protein levels in all phases of pregnancy, and several in vitro and in vivo studies demonstrated functional activity of the transporter in materno-fetal drug transport. P-gp is able to actively pump drugs and other xenobiotics from trophoblast cells back to the maternal circulation, providing thus protection to the fetus. This review summarizes the current knowledge on the expression, localization and function of P-gp in the placenta. In addition, we include the latest data concerning transcriptional regulation of placental P-gp expression and polymorphisms of the MDR1 gene. Clinical significance of placental P-gp and its future perspectives for pharmacotherapy during pregnancy are also discussed.

Targeting postprandial hyperglycemia

In healthy individuals, blood glucose levels in the fasting state are maintained by the continuous basal-level insulin secretion. After a meal, the rise in postprandial glucose (PPG) is controlled by the rapid pancreatic release of insulin, stimulated by both glucose and the intestinal production of the incretins glucose-dependent insulinotropic polypeptide and glucagon-like peptide 1. In diabetic individuals, postprandial insulin secretion is insufficient to suppress an excessive rise in PPG. There is increasing evidence that elevated PPG exerts a more deleterious effect on the vascular system than elevation of fasting plasma glucose. In particular, individuals with normal fasting plasma glucose but impaired glucose tolerance have significantly increased risk of cardiovascular events. With the recognition of the importance of PPG and the availability of new pharmacologic options, management of diabetes will shift to greater attention to PPG levels. The prototype for such an approach is in the treatment of gestational diabetes and diabetic pregnancies where PPG is the primary target of efforts at glycemic control. These efforts have been extremely successful in improving the outlook for diabetic pregnant women. There are many approaches to reduction of PPG; dietary management and promotion of exercise are very effective. Sulfonylureas, meglitinides, metformin, thiazolidinediones, and disaccharidase inhibitors all counteract PPG elevation. The development of glucagon-like peptide 1 agonists such as exendin and dipeptidyl peptidase IV inhibitors such as vildagliptin offers a new approach to suppression of PPG elevation. New semisynthetic insulin analogues permit a more aggressive response to postprandial glucose elevation, with lower risk of hypoglycemia, than with regular insulin. Inhaled insulin also has a rapid onset of action and offers benefits in PPG control. It is proposed that an aggressive treatment approach focusing on PPG, similar to the current standards for diabetic pregancies, be directed at individuals with diabetes and impaired glucose tolerance.

Perfusion studies of glyburide transfer across the human placenta: implications for fetal safety

OBJECTIVE

Gestational diabetes affects up to 5% of women. Oral hypoglycemics have been avoided because of the assumption that their placental transfer may cause fetal-neonatal hypoglycemia. A recent randomized trial could not show measurable glyburide levels in umbilical blood despite maternal treatment with regular doses of glyburide. The mechanism underlying this phenomenon is not known. The objective of our study was to document, using a human placenta perfusion model, whether glyburide is actively effluxed from the fetal to the maternal circulation.

STUDY DESIGN

In vitro perfusion studies of human cotyledon were performed to quantify placental transfer of glyburide. Using close circle experiments and introducing glyburide to both maternal and fetal circulations at 200 ng/mL, we looked for evidence of transport against concentration gradient from the fetus to the mother. In parallel experiments, the P-glycoprotein inhibitor verapamil was used in an attempt to inhibit transplacental glyburide movement.

RESULTS

There was highly significant transfer of glyburide against concentration gradient from the fetal to the maternal circulation. Fetal-to-maternal concentration ratio was 0.92 +/- 0.23 at the start of the experimental period and 0.31 +/- 0.47 3 hours later (P = .01) (n = 5). Verapamil did not modify glyburide transport.

CONCLUSION

This is the first direct evidence of active glyburide transport from the fetus to the mother and, in general, of any medicinal drug used during pregnancy. These experiments suggest that glyburide is actively efflux by a transporter other than P-glycoprotein. Alternatively, it is possible that a minority of glyburide is carried by P-glycoprotein, but most of the fetal load is pumped to the mother by a yet-unidentified placental transport system.

Perinatal outcomes and the use of oral hypoglycemic agents

OBJECTIVE

To compare neonatal results from patients with gestational diabetes mellitus (GDM) who were treated with insulin, glyburide and acarbose.

RESULTS

Seventy patients diagnosed with GDM who needed therapy to complement diet and physical activities were included in the study. One group was assigned to insulin therapy (n = 27), a second group was assigned to glyburide therapy (n = 24) and a third group was assigned to acarbose therapy (n = 19). Maternal characteristics were similar in the three groups. Glucose control was not achieved in five (20.8%) of the patients using glyburide and in eight (42.1%) of patients using acarbose. No statistical difference was observed in fasting and post-prandial glucose levels or in average newborn weight in the three groups. The rate of large for gestational age (LGA) fetuses was 3.7, 25 and 10.5% in the groups treated with insulin, glyburide and acarbose, respectively. Neonatal hypoglycemia was observed in eight newborns, six of which from the glyburide group.

CONCLUSION

We believe that glyburide and acarbose can be promising alternative therapies for the treatment of GDM. Glyburide controlled glucose levels in most patients and it was more efficient than acarbose. Glyburide showed a higher rate of macrosomia and neonatal hypoglycemia as compared to other therapies.

Population Pharmacokinetics of Metformin in Late Pregnancy

The pharmacokinetic disposition of metformin in late pregnancy was studied together with the level of fetal exposure at birth. Blood samples were obtained in the third trimester of pregnancy from women with gestational diabetes or type 2 diabetes; 5 had a previous diagnosis of polycystic ovary syndrome. A cord blood sample also was obtained at the delivery of some of these women, and also at delivery of others who had been taking metformin during pregnancy but from whom no blood had been taken. Plasma metformin concentrations were assayed by a new, validated, reverse-phase HPLC method. A 2-compartment, extravascular maternal model with transplacental partitioning of drug to a fetal compartment was fitted to the data. Nonlinear mixed-effects modeling was performed in NONMEM using FOCE with INTERACTION. Variability was estimated using logarithmic interindividual and additive residual variance models; the covariance between clearance and volume was modeled simultaneously. Mean (range) metformin concentrations in cord plasma and in maternal plasma were 0.81 (range, 0.1-2.6) mg/L and 1.2 (range, 0.1-2.9) mg/L, respectively. Typical population values (interindividual variability, CV%) for allometrically scaled maternal clearance and volume of distribution were 28 L/h/70 kg (17.1%) and 190 L/70 kg (46.3%), giving a derived population-wide half-life of 5.1 hours. The placental partition coefficient for metformin was 1.07 (36.3%). Neither maternal age nor weight significantly influenced the pharmacokinetics. The variability (SD) of observed concentrations about model-predicted concentrations was 0.32 mg/L. The pharmacokinetics were similar to those in nonpregnant patients and, therefore, no dosage adjustment is warranted. Metformin readily crosses the placenta, exposing the fetus to concentrations approaching those in the maternal circulation. The sequelae to such exposure, eg, effects on neonatal obesity and insulin resistance, remain unknown.

Recent advances in the treatment of gestational diabetes

Despite four decades of research there is a lack of international consensus on the screening, diagnosis, treatment and follow up of gestational diabetes mellitus (GDM). Currently, GDM is managed by diet modification, exercise and exogenous human insulin. During the last decade, several insulin analogues and oral antihyperglycaemic drugs have revolutionised the management of diabetes mellitus in non-pregnant women. Most of these recent drugs still remain investigational in GDM due to concerns about their safety in pregnancy. This review will focus primarily on the pharmacological treatment of GDM. It will objectively assess the value of these exciting new drugs in pregnancy as they could potentially benefit every woman with GDM.

Oral Hypoglycemic Agents in Pregnancy

Pregnancies in diabetic women are associated with increased risk of spontaneous abortion, congenital malformations, preeclampsia, preterm labor, macrosomia, shoulder dystocia, and cesarean section. Advances in antepartum cares and strict adherence to dietary and insulin regimens have been shown to significantly reduce the rate of maternal morbidity as well as perinatal morbidity and mortality. Historically, reports of potential fetal teratogenicity and hypoglycemic effects on the fetus contraindicated the use of oral hypoglycemic agents in pregnancies complicated with either type II diabetes mellitus (DM) or gestational diabetes mellitus (GDM). Recently, physicians increasingly prescribe newer generations of oral hypoglycemic agents to treat GDM and type II DM to pregnant patients. This review addresses the safety, current recommendations, and controversies surrounding use of the available oral hypoglycemic agents during pregnancy.

TARGET AUDIENCE

Obstetricians & Gynecologists, Family Physicians

LEARNING OBJECTIVES

After completion of this article, the reader should be able to describe the mechanisms of actions of the various oral hypoglycemic agents, to list the known side effects of these agents, and to summarize the data on the use of these agents during pregnancy.