Effect of posture on creatinine clearance in late pregnancy and after pregnancy

Urinary Clearance of 11-Nor-9-Carboxy-Δ9 -Tetrahydrocannabinol (THCCOOH): A Detailed Pharmacokinetic Analysis

BACKGROUND

Urine is a common matrix for screening for cannabis use. Urine assays typically measure total THCCOOH concentrations after hydrolysis cleaves the glucuronide. Urine THCCOOH concentration is adjusted by urine creatinine concentration or specific gravity, to account for variable hydration states. Therefore, we performed a population pharmacokinetic analysis of the urinary THCCOOH excretion, urinary flow rate, and creatinine excretion rate data.

METHODS

Urine was obtained over 168 hours from 6 subjects who smoked low (15.8 mg) and high dose (33.8 mg) THC cigarettes on two occasions. Samples were analyzed for THCCOOH concentration by GC/MS and volume, time and creatinine concentration measured. A population pharmacokinetic model of the urinary clearance of THCCOOH was created from these data and potential covariates of urine creatinine concentration and urine creatinine excretion rate were assessed.

RESULTS

Elimination clearance of THCCOOH was estimated as 0.104 ± 0.088 L/min and its urinary clearance was 0.0022 ± 0.0015 L/min. Total urine excretion of THCCOOH was estimated a 2.3%. Urine flow rate and urine creatinine concentrations were significantly correlated, r² 0.35. Creatinine excretion rate was 129.6 ± 71.0 mL/min and the intra-subject variability was 31-52% (SD%) during the week. Urinary creatinine excretion rate was a significant covariate for the urinary clearance of THCCOOH.

CONCLUSIONS

Creatinine Clearance is a significant covariate for urinary THCCOOH clearance. Only 2-3% of bioavailable THC is excreted as THCCOOH and THCCOO-glucuronide via the urine. Correction of urine drug and/or metabolite concentration with urine creatinine concentration or specific gravity may be more problematic than previously appreciated.

Association between prenatal phthalate exposure and gestational metabolic syndrome parameters: a systematic review of epidemiological studies

The relationship of intrauterine phthalate exposure with gestational metabolic syndrome (GMS) parameters is inconsistently reported. We performed a systematic review to evaluate the association between prenatal phthalate exposure and GMS parameters. A literature search was performed in three databases. According to the defined PECOS statement, eligible studies were identified. The method and result for each study was qualitatively summarized with great emphasis on study design and exposure assessment. Fourteen studies were included in the present systematic review. Two studies used one-spot serum sample for evaluation of phthalate exposure, while others used 1-4 urine samples. Concentrations of phthalate metabolites varied substantially, and the levels in serum were greatly lower than those in urine. These studies observed no interstudy or intrastudy consistency for association between phthalates and GMS in pregnant women cross-sectionally or longitudinally, regardless of phthalates species or GMS indicator. Most reported associations were not significantly different from null result. Besides, positive and negative relationships also existed. The current epidemiological data do not support the hypothesis that prenatal exposure to phthalates increases GMS risk.

Maternal kidney function during pregnancy: systematic review and meta-analysis

OBJECTIVES

To review systematically current literature on kidney function changes during pregnancy, in order to estimate the extent of adaptation over the course of both healthy physiological and complicated singleton pregnancies, and to determine healthy pregnancy reference values.

METHODS

PubMed (NCBI) and EMBASE (Ovid) electronic databases were searched, from inception to July 2017, for studies on kidney function during uncomplicated and complicated pregnancies. Included studies were required to report a non-pregnant reference value of kidney function (either in a non-pregnant control group or as a prepregnancy or postpartum measurement) and a pregnancy measurement at a predetermined and reported gestational age. Kidney function measures assessed were glomerular filtration rate (GFR) measured by inulin clearance, GFR measured by creatinine clearance and serum creatinine level. Pooled mean differences between pregnancy measurements and reference values were calculated for predefined intervals of gestational age in uncomplicated and complicated pregnancies using a random-effects model described by DerSimonian and Laird.

RESULTS

Twenty-nine studies met the inclusion criteria and were included in the analysis. As early as the first trimester, GFR was increased by up to 40-50% in physiological pregnancy when compared with non-pregnant values. Inulin clearance in uncomplicated pregnancy was highest at 36-41 weeks, with a 55.6% (53.7; 95% CI, 44.7-62.6 mL/min) increase when compared with non-pregnant values, and creatinine clearance was highest at 15-21 weeks' gestation, with a 37.6% (36.6; 95% CI, 26.2-46.9 mL/min) increase. Decrease in serum creatinine level in uncomplicated pregnancy was most prominent at 15-21 weeks, with a 23.2% (-0.19; 95% CI, -0.23 to -0.15 mg/dL) decrease when compared with non-pregnant values. Eight studies reported on pregnancies complicated by a hypertensive disorder. Meta-regression analysis showed a significant difference in all kidney function parameters when comparing uncomplicated and hypertensive complicated pregnancies.

CONCLUSIONS

In healthy pregnancy, GFR is increased as early as the first trimester, as compared with non-pregnant values, and the kidneys continue to function at a higher rate throughout gestation. In contrast, kidney function is decreased in hypertensive pregnancy. © 2018 The Authors. Ultrasound in Obstetrics & Gynecology published by John Wiley & Sons Ltd on behalf of the International Society of Ultrasound in Obstetrics and Gynecology.

Serum Creatinine in Pregnancy: A Systematic Review

Introduction

Standard assessment of renal function in pregnancy is by measurement of serum creatinine concentration yet normal gestational ranges have not been established. The aim of this systematic review was to define the difference in serum creatinine in a healthy pregnancy compared with concentrations in nonpregnant women to facilitate identification of abnormal kidney function in pregnancy.

Methods

Medline, PubMed, Embase, Web of Science, theses, key obstetric texts, and conference proceedings were searched to July 2017. Eligible studies included quantification of serum creatinine concentration in a pregnant cohort, with either a reported local laboratory reference range or matched quantification in a nonpregnant cohort. The outcomes of interest were the mean and upper reference limits for creatinine in pregnancy, measured as a ratio of pregnant:nonpregnant values. Study heterogeneity was examined by meta-regression analysis.

Results

Forty-nine studies were identified. Data synthesis included 4421 serum creatinine values in pregnancy, weighted according to cohort size. Mean values for serum creatinine in pregnancy were 84%, 77%, and 80% of nonpregnant mean values during the first, second, and third trimesters, respectively. The 97.5th centile (upper limit of the 95% reference range) for serum creatinine in pregnancy was 85%, 80%, and 86% of the nonpregnant upper limit in sequential trimesters.

Conclusion

Based on a nonpregnant reference interval of 45–90 μmol/l (0.51–1.02 mg/dl), a serum creatinine of >77 μmol/l (0.87 mg/dl) should be considered outside the normal range for pregnancy. Future work can use this value to explore correlation of adverse pregnancy outcomes with serum creatinine concentration. PROSPERO registration: CRD42017068446

Pregnancy in diabetes and kidney disease

With appropriate multi-disciplinary team care, most women with diabetic nephropathy will have successful pregnancy outcomes; however, pregnancy complications are increased compared to non-diabetic individuals, particularly in those with poor glycaemic control. Women with more severe renal impairment, especially those with hypertension and proteinuria at are highest risk of worse pregnancy outcomes and deterioration in pre-existing renal function. Pre-pregnancy counselling should be offered to all women with diabetes in order to optimise diabetic care, and inform women of potential complications. Pregnancy is an indicator of long-term health, and may indicate important issues for the future management of women with diabetic nephropathy.

Urinary phthalate metabolites in relation to preterm birth in Mexico city

BACKGROUND

Rates of preterm birth have been rising over the past several decades. Factors contributing to this trend remain largely unclear, and exposure to environmental contaminants may play a role.

OBJECTIVE

We investigated the relationship between phthalate exposure and preterm birth.

METHODS

Within a large Mexican birth cohort study, we compared third-trimester urinary phthalate metabolite concentrations in 30 women who delivered preterm (< 37 weeks of gestation) with those of 30 controls (> or = 37 weeks of gestation).

RESULTS

Concentrations of most of the metabolites were similar to those reported among U.S. females, although in the present study mono-n-butyl phthalate (MBP) concentrations were higher and monobenzyl phthalate (MBzP) concentrations lower. In a crude comparison before correcting for urinary dilution, geometric mean urinary concentrations were higher for the phthalate metabolites MBP, MBzP, mono(3-carboxylpropyl) phthalate, and four metabolites of di(2-ethyl-hexyl) phthalate among women who subsequently delivered preterm. These differences remained, but were somewhat lessened, after correction by specific gravity or creatinine. In multivariate logistic regression analysis adjusted for potential confounders, elevated odds of having phthalate metabolite concentrations above the median level were found.

CONCLUSIONS

We found that phthalate exposure is prevalent among this group of pregnant women in Mexico and that some phthalates may be associated with preterm birth.