Effects of maternal ritodrine administration on neonatal renal function

Prediction of glomerular filtration rate maturation across preterm and term neonates and young infants using inulin as marker

Describing glomerular filtration rate (GFR) maturation across the heterogeneous population of preterm and term neonates and infants is important to predict the clearance of renally cleared drugs. This study aims to describe the GFR maturation in (pre)term neonates and young infants (PNA < 90 days) using individual inulin clearance data (CL_inulin). To this end, published GFR maturation models were evaluated by comparing their predicted GFR with CL_inulin retrieved from literature. The best model was subsequently optimized in NONMEM V7.4.3 to better fit the CL_inulin values. Our study evaluated seven models and collected 381 individual CL_inulin values from 333 subjects with median (range) birthweight (BWb) 1880 g (580-4950), gestational age (GA) 34 weeks (25-43), current weight (CW) 1890 g (480-6200), postnatal age (PNA) 3 days (0-75), and CL_inulin 2.20 ml/min (0.43-17.90). The De Cock 2014 model (covariates: BWb and PNA) performed the best in predicting CL_inulin, followed by the Rhodin 2009 model (covariates: CW and postmenstrual age). The final optimized model shows that GFR at birth is determined by BWb, thereafter the maturation rate of GFR is dependent on PNA and GA, with a higher GA showing an overall faster maturation. To conclude, using individual CL_inulin data, we found that a model for neonatal GFR requires a distinction between prenatal maturation quantified by BWb and postnatal maturation. To capture postnatal GFR maturation in (pre)term neonates and young infants, we developed an optimized model in which PNA-related maturation was dependent on GA.

Development of a Novel Maternal-Fetal Physiologically Based Pharmacokinetic Model I: Insights into Factors that Determine Fetal Drug Exposure through Simulations and Sensitivity Analyses

Determining fetal drug exposure (except at the time of birth) is not possible for both logistical and ethical reasons. Therefore, we developed a novel maternal-fetal physiologically based pharmacokinetic (m-f-PBPK) model to predict fetal exposure to drugs and populated this model with gestational age-dependent changes in maternal-fetal physiology. Then, we used this m-f-PBPK to: 1) perform a series of sensitivity analyses to quantitatively demonstrate the impact of fetoplacental metabolism and placental transport on fetal drug exposure for various drug-dosing regimens administered to the mother; 2) predict the impact of gestational age on fetal drug exposure; and 3) demonstrate that a single umbilical venous (UV)/maternal plasma (MP) ratio (even after multiple-dose oral administration to steady state) does not necessarily reflect fetal drug exposure. In addition, we verified the implementation of this m-f-PBPK model by comparing the predicted UV/MP and fetal/MP AUC ratios with those predicted at steady state after an intravenous infusion. Our simulations yielded novel insights into the quantitative contribution of fetoplacental metabolism and/or placental transport on gestational age-dependent fetal drug exposure. Through sensitivity analyses, we demonstrated that the UV/MP ratio does not measure the extent of fetal drug exposure unless obtained at steady state after an intravenous infusion or when there is little or no fluctuation in MP drug concentrations after multiple-dose oral administration. The proposed m-f-PBPK model can be used to predict fetal exposure to drugs across gestational ages and therefore provide the necessary information to assess the risk of drug toxicity to the fetus.

Effects of maternally administered drugs on the fetal and neonatal kidney

The number of pregnant women and women of childbearing age who are receiving drugs is increasing. A variety of drugs are prescribed for either complications of pregnancy or maternal diseases that existed prior to the pregnancy. Such drugs cross the placental barrier, enter the fetal circulation and potentially alter fetal development, particularly the development of the kidneys. Increased incidences of intrauterine growth retardation and adverse renal effects have been reported. The fetus and the newborn infant may thus experience renal failure, varying from transient oligohydramnios to severe neonatal renal insufficiency leading to death. Such adverse effects may particularly occur when fetuses are exposed to NSAIDs, ACE inhibitors and specific angiotensin II receptor type 1 antagonists. In addition to functional adverse effects, in utero exposure to drugs may affect renal structure itself and produce renal congenital abnormalities, including cystic dysplasia, tubular dysgenesis, ischaemic damage and a reduced nephron number. Experimental studies raise the question of potential long-term adverse effects, including renal dysfunction and arterial hypertension in adulthood. Although neonatal data for many drugs are reassuring, such findings stress the importance of long-term follow-up of infants exposed in utero to certain drugs that have been administered to the mother.

Clinical pharmacokinetics of beta-agonists

The beta-agonists have found wide clinical use as racemic mixtures for 20 years, but information on their pharmacokinetics is not comprehensive. They are well absorbed orally, but have low systemic availability due to extensive first-pass sulphation. When administered by inhalation, very little of the administered dose reaches the lungs, but the small amount that does produces effective bronchodilatation. Plasma protein binding of most beta-agonists is negligible, and there is substantial extravascular distribution of the administered dose. Elimination of intravenous drug is predominantly renal, whereas oral doses are mostly eliminated by biotransformation. Renal clearance correlates with creatinine clearance; therefore, dose reduction should be considered if renal function is impaired, such as in the elderly or in cardiac failure. The elimination half-life of most beta-agonists is relatively short, and pharmacokinetics are independent of dose and duration of treatment. Differences in the pharmacokinetics of the enantiomers are evident. There is very large variation in pharmacodynamic response for a given plasma beta 2-agonist concentration among different subjects, and as treatment proceeds in an individual subject. Therefore, in most cases therapeutic response and side effects are more useful for the monitoring of beta 2-agonist treatment than measurement of plasma drug concentrations. The pharmacokinetics of beta 2-agonists are not greatly altered in pregnancy although these agents cause a marked reduction in maternal renal function. Placental transfer is relatively rapid, and side effects are observed in fetus and neonate. Elimination may be somewhat faster in children (8 to 15 years) than in young adults. Asthma does not appear to influence the pharmacokinetics of beta 2-agonists; the only recorded drug interaction of clinical significance is an increase in theophylline clearance by intravenous isoprenaline (isoproterenol). Controlled release oral preparations do not reduce side effects, but may improve compliance due to less frequent dosing. The application of pharmacokinetic principles may improve the clinical usage of beta-agonists, at least when they are used in premature labour and in cardiac failure.

Mineral balance studies in sick preterm intravenously fed infants during the first week after birth. A guide to fluid therapy

Mineral balance studies were performed in 61 sick preterm infants given parenteral fluids only. Their gestational ages varied from 24 to 35 weeks, and 50 required mechanical ventilation. Two consecutive balance studies were performed; the first from admission to 48 hours in all babies given maintenance fluids of 10% Dextrose, and the second from 48 hours to 7 days in those babies given intravenous feeding (IVN). At the beginning and end of each balance period, the baby was weighed and an arterial blood sample taken for blood gases, electrolyte, urea, creatinine and protein determinations. During the balance period all urine was collected and analysed for electrolyte, urea, and creatinine composition, and all fluid intake was recorded. The balance of a mineral was calculated as the difference between parenteral intake and urine output. Infants requiring IVN were allocated alternatively to regimen X or regimen Y, which had the same calcium content of 9.5 mmol/L, but different phosphate contents, regimen X containing 7.3 mmol/L and regimen Y 11.6 mmol/L. In those infants requiring prolonged IVN, 12-24 hour balance studies were performed at weekly intervals after day 10. 1. Phosphate deficiency developed in infants given regimen X, who had higher urine calcium excretion, lower percentage calcium retention and lower plasma phosphate levels than those given regimen Y. These differences were apparent by day 7 and persisted after day 10. In infants given regimen Y, mean calcium retention from admission to day 7 was 3.9 mmol/kg, and after day 10 was 0.9 mmol/kg/day. 2. In the first 48 hours, urine output and creatinine clearance varied widely and were lower in infants with higher oxygen requirements at 48 hours. Ten babies had severe oliguria with outputs less than 10 mL/kg/day. Creatinine clearance was directly related to gestational age, mean arterial blood pressure, and plasma protein concentrations on admission. After 48 hours, urine output and creatinine clearance increased considerably. 3. In the first 48 hours, metabolic acidosis was produced by increased plasma non-protein metabolisable acid concentrations, which were associated with low creatinine clearances, and were thought to be due to lactic acid accumulation in response to decreased tissue perfusion. At 7 days, metabolic acidosis was of similar severity but was produced by decreased plasma non-metabolisable base concentrations, caused by increased urine loss of net base, and not directly by IVN.(ABSTRACT TRUNCATED AT 400 WORDS)

The association between decreased amniotic fluid volume and treatment with nonsteroidal anti-inflammatory agents for preterm labor

From a cohort of women treated for preterm labor at the Swedish Hospital Medical Center for a 1-year period, 58 patients were identified as receiving one or more tocolytic agents. Twenty-seven of the 58 patients met study criteria for the determination of the effects of tocolytic therapy on amniotic fluid volume both before and during treatment by means of ultrasound examination. Fourteen of 17 patients (82.3%) treated with nonsteroidal anti-inflammatory drugs demonstrated a decrease in amniotic fluid, whereas none of the 10 patients treated with other tocolytic agents experienced a decrease in fluid volume. Decreased amniotic fluid associated with nonsteroidal anti-inflammatory drug treatment was reversible in seven of eight patients when treatment was discontinued and ultrasound examinations were performed after treatment.

Fetal renal failure associated with intrauterine growth retardation

Four preterm infants with severe intrauterine growth retardation had renal failure from birth. The amount of asphyxia associated with the birth process did not fully explain the renal failure. Before delivery all for fetuses had severe oligohydramnios and an empty urinary bladder. These observations strengthen the view that severe intrauterine growth retardation may be accompanied by oligohydramnios caused by fetal renal failure.

Oligohydramnios, renal insufficiency, and ileal perforation in preterm infants after intrauterine exposure to indomethacin

Three preterm infants exposed antenatally to indomethacin developed a characteristic syndrome consisting of edema and hydrops with a bleeding disorder at birth, oliguric renal failure during the first 3 postnatal days, and acute pneumoperitoneum resulting from localized ileal perforation(s) at the end of the first week of life. Despite the value of indomethacin for arresting preterm labor, the physician must take into account the potential hazards of drug toxicity.

Maturation of glomerular filtration in preterm and mature babies

Glomerular filtration rate (GFR) was measured in 39 healthy infants (gestation 27-40 weeks, birthweight 0.68-3.71 kg) by prolonged inulin infusion between 2 and 63 days of age. Absolute GFR showed a logarithmic rise with conceptional age (gestational plus postnatal age) which was independent of postnatal age. GFR per kilogram showed a slow rise with gestational age, and a rapid rise with increasing postnatal age which was shown to be due to a temporary cessation of growth rather than a true acceleration in renal maturation. GFR per unit surface area showed similar, but steeper rises. Formulae were constructed to predict GFR in the first month of life from postnatal age (PA), weight and birthweight (BW); (GFR = (0.24 BW + 0.18 PA + 0.45) X weight), or from conceptional age (CA); (GFR = 100.0618 CA-1.859). 95% of the predictions fell within 66 and 151%, and 58 and 172% of the measured values, respectively. Data from 14 studies were expressed in the same format where possible. The agreement between the reported data and this study was close. Apparent contradictions between these studies had been largely due to their different forms of presentation.