Magnesium sulphate for prevention of eclampsia: are intramuscular and intravenous regimens equivalent? A population pharmacokinetic study

A follow up on the feasibility after national implementation of magnesium sulfate for neuroprotection prior to preterm birth

INTRODUCTION

The risk for brain injury manifested as cerebral palsy is higher in very preterm born children than in term. Prenatal administration of magnesium sulfate (MgSO4 ) has been shown to be neuroprotective and reduces the proportion of very preterm born children later diagnosed with cerebral palsy. A Swedish national clinical practice guideline was implemented in March 2020, stipulating the administration of a single intravenous dose of 6 g MgSO4 1-24 h prior to delivery before gestational age 32+0, aiming for 90% treatment coverage. The aim of this study was to evaluate the feasibility of this new clinical practice guideline in the first year of its implementation.

MATERIAL AND METHODS

Data on MgSO4 treatment were collected by reviewing the medical charts of women who gave birth to live born children in gestational age 22+0-31+6 during the period of March 1, 2020 to February 28, 2021, at five Swedish university hospitals. Women with pre-eclampsia, eclampsia, or high elevated liver enzymes low platelets (HELLP) were excluded.

RESULTS

A total of 388 women were eligible and 79% received treatment with MgSO4 . Of the 21% not receiving treatment, 9% did not receive treatment due to lack of knowledge about the clinical practice guideline, 9% were not possible to treat and 3% had missing data. The proportion treated increased from 72% to 87% from the first to the last 3 months. Of those treated, 81% received the drug within the stipulated timeframe (mean 8.7 h, median 3.4 h).

CONCLUSIONS

There was a positive trend over time in the proportion of women receiving MgSO4 treatment, but the a priori target of 90% was not reached during the first year of implementation. Our findings indicate that this target could be reached with additional information to clinicians.

Alternative magnesium sulphate regimens for women with pre-eclampsia and eclampsia

BACKGROUND

Magnesium sulphate is the drug of choice for the prevention and treatment of women with eclampsia. Regimens for administration of this drug have evolved over the years, but there is no clarity on the comparative benefits or harm of alternative regimens. This is an update of a review first published in 2010.

OBJECTIVES

To assess if one magnesium sulphate regimen is better than another when used for the care of women with pre-eclampsia or eclampsia, or both, to reduce the risk of severe morbidity and mortality for the woman and her baby.

SEARCH METHODS

We searched Cochrane Pregnancy and Childbirth's Trials Register, ClinicalTrials.gov, the WHO International Clinical Trials Registry Platform (29 April 2022), and reference lists of retrieved studies.

SELECTION CRITERIA

We included randomised trials and cluster-randomised trials comparing different regimens for administration of magnesium sulphate used in women with pre-eclampsia or eclampsia, or both. Comparisons included different dose regimens, intramuscular versus intravenous route for maintenance therapy, and different durations of therapy. We excluded studies with quasi-random or cross-over designs. We included abstracts of conference proceedings if compliant with the trustworthiness assessment.

DATA COLLECTION AND ANALYSIS

For this update, two review authors assessed trials for inclusion, performed risk of bias assessment, and extracted data. We checked data for accuracy. We assessed the certainty of the evidence using the GRADE approach.

MAIN RESULTS

For this update, a total of 16 trials (3020 women) met our inclusion criteria: four trials (409 women) compared regimens for women with eclampsia, and 12 trials (2611 women) compared regimens for women with pre-eclampsia. Most of the included trials had small sample sizes and were conducted in low- and middle-income countries. Eleven trials reported adequate randomisation and allocation concealment. Blinding of participants and clinicians was not possible in most trials. The included studies were for the most part at low risk of attrition and reporting bias. Treatment of women with eclampsia (four comparisons) One trial compared a loading dose-alone regimen with a loading dose plus maintenance dose regimen (80 women). It is uncertain whether either regimen has an effect on the risk of recurrence of convulsions or maternal death (very low-certainty evidence). One trial compared a lower-dose regimen with standard-dose regimen over 24 hours (72 women). It is uncertain whether either regimen has an effect on the risk of recurrence of convulsion, severe morbidity, perinatal death, or maternal death (very low-certainty evidence). One trial (137 women) compared intravenous (IV) versus standard intramuscular (IM) maintenance regimen. It is uncertain whether either route has an effect on recurrence of convulsions, death of the baby before discharge (stillbirth and neonatal death), or maternal death (very low-certainty evidence). One trial (120 women) compared a short maintenance regimen with a standard (24 hours after birth) maintenance regimen. It is uncertain whether the duration of the maintenance regimen has an effect on recurrence of convulsions, severe morbidity, or side effects such as nausea and respiratory failure. A short maintenance regimen may reduce the risk of flushing when compared to a standard 24 hours maintenance regimen (risk ratio (RR) 0.27, 95% confidence interval (CI) 0.08 to 0.93; 1 trial, 120 women; low-certainty evidence). Many of our prespecified critical outcomes were not reported in the included trials. Prevention of eclampsia for women with pre-eclampsia (five comparisons) Two trials (462 women) compared loading dose alone with loading dose plus maintenance therapy. Low-certainty evidence suggests an uncertain effect with either regimen on the risk of eclampsia (RR 2.00, 95% CI 0.61 to 6.54; 2 trials, 462 women) or perinatal death (RR 0.50, 95% CI 0.19 to 1.36; 2 trials, 462 women). One small trial (17 women) compared an IV versus IM maintenance regimen for 24 hours. It is uncertain whether IV or IM maintenance regimen has an effect on eclampsia or stillbirth (very low-certainty evidence). Four trials (1713 women) compared short postpartum maintenance regimens with continuing for 24 hours after birth. Low-certainty evidence suggests there may be a wide range of benefit or harm between groups regarding eclampsia (RR 1.99, 95% CI 0.18 to 21.87; 4 trials, 1713 women). Low-certainty evidence suggests there may be little or no effect on severe morbidity (RR 0.96, 95% CI 0.71 to 1.29; 2 trials, 1233 women) or side effects such as respiratory depression (RR 0.80, 95% CI 0.25 to 2.61; 2 trials, 1424 women). Three trials (185 women) compared a higher-dose maintenance regimen versus a lower-dose maintenance regimen. It is uncertain whether either regimen has an effect on eclampsia (very low-certainty evidence). Low-certainty evidence suggests that a higher-dose maintenance regimen has little or no effect on side effects when compared to a lower-dose regimen (RR 0.79, 95% CI 0.61 to 1.01; 1 trial 62 women). One trial (200 women) compared a maintenance regimen by continuous infusion versus a serial IV bolus regimen. It is uncertain whether the duration of the maintenance regimen has an effect on eclampsia, side effects, perinatal death, maternal death, or other neonatal morbidity (very low-certainty evidence). Many of our prespecified critical outcomes were not reported in the included trials.

AUTHORS' CONCLUSIONS

Despite the number of trials evaluating various magnesium sulphate regimens for eclampsia prophylaxis and treatment, there is still no compelling evidence that one particular regimen is more effective than another. Well-designed randomised controlled trials are needed to answer this question.

Magnesium Sulfate Use in Pregnancy for Preeclampsia Prophylaxis and Fetal Neuroprotection: Regimens in High-Income and Low/Middle-Income Countries

Magnesium sulfate is one of the most commonly used medications in obstetrics, most notably for the prevention of eclamptic seizures and fetal neuroprotection of the extremely preterm neonate. Pharmacokinetic and pharmacodynamic studies have demonstrated a variety of IV and IM regimens are effective for these indications. Existing models and data can be used to tailor treatment regimens to increase coverage in poor resource areas, maximize efficacy and minimize toxicity for patients of different weights and renal function.

A retrospective review of the risk factors affecting the therapeutic serum concentrations of magnesium sulfate in pre-eclamptic patients

WHAT IS KNOWN AND OBJECTIVE

To identify factors that may affect the therapeutic serum magnesium levels after intravenous administration for seizure prophylaxis in pre-eclamptic patients.

METHODS

One hundred and two women with PE with severe features were identified categorized into two groups: subtherapeutic and therapeutic group. Multivariate logistic regression analysis and receiver operation characteristic curve analysis were conducted for the risk factors influencing the serum magnesium concentration.

RESULTS

Among 102 eligible patients, 63 (62%) patients did not attain ideal therapeutic serum magnesium levels. Those patients had elevated albumin levels (p < 0.05), higher creatinine clearance (Ccr) (p < 0.001), and higher body mass index (BMI) (p < 0.001). Logistic regression analysis identified BMI and Ccr as independent risk factors for subtherapeutic serum magnesium concentration (p < 0.05). Receiver operating characteristic (ROC) curve analysis revealed a greater area under the curve for BMI than for Ccr in predicting subtherapeutic serum magnesium levels (0.787 vs. 0.774).

WHAT IS NEW AND CONCLUSION

Maternal body weight and renal function were independent risk factors for subtherapeutic serum magnesium concentration in the early stage after administration.

Magnesium sulfate pharmacokinetics after intramuscular dosing in women with preeclampsia

BACKGROUND

Current intramuscular magnesium dosing regimens in low and middle-income countries are based on indirect absorption parameters to inform pharmacokinetic and pharmacodynamic response.

OBJECTIVE

To determine if therapeutic serum magnesium levels are obtained in women with severe preeclampsia receiving intramuscular administration of magnesium sulfate using the Pritchard regimen and to compare the key pharmacokinetic variables to those previously published.

STUDY DESIGN

Serum magnesium levels were obtained at multiple time points at baseline and after magnesium sulfate administration from women with severe preeclampsia receiving the standard Pritchard regimen for seizure prophylaxis at Bayero University, Kano, Nigeria. The pharmacokinetic profiles were constructed for the study cohort and the updated pharmacokinetic model was compared with the one that was previously published.

RESULTS

A total of 80 blood samples were collected from 20 women with severe preeclampsia (45 collected before childbirth and 35 collected after childbirth). After 11.5 hours of magnesium sulfate administration, 63% of women in the cohort had serum magnesium levels of ≥2.0 mmol/L. Data from women receiving the Pritchard regimen combined with data from women previously modeled after the receipt of intravenous magnesium sulfate were adequately described using a 2-compartment model with first-order absorption and linear elimination from the central compartment. All structural pharmacokinetic parameters including clearance, central volume of distribution, peripheral volume of distribution, and intercompartment clearance were adjusted for maternal weight, and the clearance was further adjusted for serum creatinine level and antepartum or postpartum status. The simulated pharmacokinetic profiles of the updated pharmacokinetic model and the previously published pharmacokinetic model are similar. In previously published pharmacokinetic modeling, absorption rate constant=0.32 and absolute bioavailability=0.86. In the updated pharmacokinetic model, absorption rate constant=0.45 and absolute bioavailability=0.91.

CONCLUSION

These data support the use of the Pritchard regimen as acceptable to achieve therapeutic serum magnesium levels and support the reported simulation of serum magnesium levels and eclampsia response associated with different intramuscular regimens.

Factors affecting use of magnesium sulphate for pre-eclampsia or eclampsia: a qualitative evidence synthesis

Background

Hypertensive disorders account for 14% of global maternal deaths. Magnesium sulphate (MgSO₄) is recommended for prevention and treatment of pre‐eclampsia/eclampsia. However, MgSO₄ remains underused, particularly in low‐ and middle‐income countries (LMICs).

Objective

This qualitative evidence synthesis explores perceptions and experiences of healthcare providers, administrators and policy‐makers regarding factors affecting use of MgSO₄ to prevent or treat pre‐eclampsia/eclampsia.

Search strategy

We searched MEDLINE, EMBASE, Emcare, CINAHL, Global Health and Global Index Medicus, and grey literature for studies published between January 1995 and June 2021.

Selection criteria

Primary qualitative and mixed‐methods studies on factors affecting use of MgSO₄ in healthcare settings, from the perspectives of healthcare providers, administrators and policy‐makers, were eligible for inclusion.

Data collection and analysis

We applied a thematic synthesis approach to analysis, using COM‐B behaviour change theory to map factors affecting appropriate use of MgSO₄.

Main results

We included 22 studies, predominantly from LMICs. Key themes included provider competence and confidence administering MgSO₄ (attitudes and beliefs, complexities of administering, knowledge and experience), capability of health systems to ensure MgSO₄ availability at point of use (availability, resourcing and pathways to care) and knowledge translation (dissemination of research and recommendations). Within each COM‐B domain, we mapped facilitators and barriers to physical and psychological capability, physical and social opportunity, and how the interplay between these domains influences motivation.

Conclusions

These findings can inform policy and guideline development and improve implementation of MgSO₄ in clinical care. Such action is needed to ensure this life‐saving treatment is widely available and appropriately used.

Tweetable abstract

Global qualitative review identifies factors affecting underutilisation of MgSO₄ for pre‐eclampsia and eclampsia.

Global qualitative review identifies factors affecting underutilisation of MgSO₄ for pre‐eclampsia and eclampsia.

This article includes Author Insights, a video abstract available at https://vimeo.com/manage/videos/623192027

Linked article This article is commented on by LA Magee, p. 392 in this issue. To view this mini commentary visit https://doi.org/10.1111/1471-0528.16971.

Alternate Dosing Protocol for Magnesium Sulfate in Obese Women With Preeclampsia: A Randomized Controlled Trial

OBJECTIVE

To evaluate whether obese women need greater doses of magnesium sulfate to obtain therapeutic serum concentrations for eclamptic seizure prevention.

METHODS

Women with preeclampsia and a body mass index (BMI) of 35 or higher were randomly allocated to either the Zuspan regimen of magnesium sulfate (4-g intravenous [IV] loading dose, then a 1-g/h infusion) or to alternate dosing (6-g IV loading dose, then a 2-g/h infusion). Women had serum magnesium concentrations obtained at baseline, as well as after administration of magnesium sulfate at 1 hour, 4 hours, and delivery. The primary outcome was the proportion of women who had subtherapeutic serum magnesium concentrations (less than 4.8 mg/dL) 4 hours after administration. A sample size of 18 women per group was planned to compare the proportion of women with subtherapeutic serum magnesium concentrations in each group.

RESULTS

From July 12, 2016, to March 14, 2019, 89 women with preeclampsia were screened and 37 were enrolled: 18 to the Zuspan regimen and 19 to the alternate regimen. A significantly greater proportion of women administered the Zuspan regimen had subtherapeutic serum magnesium concentrations at 4 hours (100% [95% CI 59-100] vs 63% [95% CI 41-81]; P=.01) compared with women administered the alternate higher dose regimen. At 4 hours, mean concentrations were significantly higher in the alternate regimen group (3.53 mg/dL±0.3 [Zuspan regimen] vs 4.41±0.5 [alternate regimen]; P<.01).

CONCLUSION

The alternate dosing regimen of a 6-g IV loading dose followed by a 2-g/h IV maintenance dose more reliably achieves therapeutic serum magnesium concentrations (as defined by a concentration of at least 4.8 mg/dL) in obese women with preeclampsia.

CLINICAL TRIAL REGISTRATION

ClinicalTrials.gov, NCT02835339.

Population Pharmacokinetics of Magnesium Sulfate in Preeclampsia and Associated Factors

Background and Objective

The pharmacokinetic basis of magnesium sulphate (MgSO₄) dosing regimens for preeclampsia (PE) prophylaxis and treatment is not clearly established. The aim of study is to develop a population pharmacokinetic (PK) model of MgSO₄ in PE, and to determine key covariates having an effect in MgSO₄ pharmacokinetics in preeclampsia (PE) and to determine key covariates having an effect in MgSO₄ PK.

Methods

A prospective cohort study was conducted from June 2016 to February 2018 in patients with PE administered MgSO₄ as a 4-g bolus followed by continuous infusion at a rate of 1 g/h. Serum magnesium concentrations were obtained before treatment administration and 2, 6, 12, and 18 h after the initial dose. The software Monolix was used to estimate population PK parameters of MgSO₄ [clearance (CL), volume of distribution (V), half-life] and to develop a PK model with baseline patient demographic, clinical, and laboratory covariates.

Results

The study population consisted of 109 patients. The PK profile of MgSO₄ was adequately described by a one-compartment PK model. The model estimate of the population CL was 1.38 L/h; for V, it was 13.3 L; and the baseline magnesium concentration was 0.77 mmol/L (1.87 mg/dL). The baseline body weight and serum creatinine statistically influenced MgSO₄ CL and V, respectively. The model was parameterized as CL and V.

Conclusion

The PK of MgSO₄ in pregnant women with PE is significantly affected by creatinine and body weight. Pregnant women with PE and higher body weight have a higher V and, consequently, a lower elimination rate of MgSO₄. Pregnant women with PE and a higher serum creatinine value show lower CL and, therefore, lower MgSO₄ elimination rate.

Risk factors for sub-therapeutic serum concentrations of magnesium sulfate in severe preeclampsia of Chinese patients

Background

Magnesium sulfate (MgSO₄) is the standard drug for eclampsia prophylaxis and treatment. In China, the effective therapeutic serum magnesium level is 1.8–3.0 mmol/L. There is little information on how to achieve and maintain effective therapeutic concentrations. This study aimed to investigate risk factors for sub-therapeutic serum concentrations of MgSO₄ in patients with severe preeclampsia.

Methods

Patients with severe preeclampsia who received MgSO₄ intravenous infusion were retrospectively reviewed. The maternal demographic characteristics, regimens for the administration of MgSO₄, and lab test results of patients were collected. Multivariate logistic regression analysis and receiver operating characteristic (ROC) curve analysis were conducted for the risk factors influencing the serum magnesium concentration.

Results

A total of 93 patients with severe preeclampsia were included in the study. 52 (55.91%) patients did not attain therapeutic serum magnesium levels. A multivariate logistic regression analysis identified creatinine clearance (Ccr), whether the loading dose was given, and measurement time of serum magnesium concentration (referring to the time from start of MgSO4 infusion to blood draw for serum sampling) as independent risk factors for sub-therapeutic serum magnesium concentration (P < 0.05). ROC curve analysis indicated that the continuous variable Ccr had a significant predictive value for the serum magnesium concentration, which resulted in a cutoff point of 133 mL/min; while measurement time had limited predictive value, with cutoff point of 2.375 h.

Conclusions

Ccr, whether the loading dose was given, and measurement time were independent risk factors for sub-therapeutic serum magnesium concentration. A loading dose of MgSO₄ everytime before the maintenance dose, as well as the duration of MgSO4 maintenance dose of more than 2.375 h are recommended for all the patients with severe PE. Routine evaluation of serum magnesium levels is a recommended practice for women with severe PE and whose Ccr is ≥133 mL/min.

Serum magnesium levels during magnesium sulfate infusion at 1 gram/hour versus 2 grams/hour as a maintenance dose to prevent eclampsia in women with severe preeclampsia: A randomized clinical trial

BACKGROUND

Magnesium sulfate is the ideal drug for the prevention and treatment of eclampsia. Nevertheless, the best regimen for protection against eclampsia with minimal side effects remains to be established. This study aimed to compare serum magnesium levels during intravenous infusion of magnesium sulfate at 1 gram/hour versus 2 grams/hour as a maintenance dose to prevent eclampsia in pregnant and postpartum women with severe preeclampsia.

METHODS

A randomized, triple-blind clinical trial was conducted, comparing serum magnesium levels during the intravenous infusion of magnesium sulfate at 1 gram/hour versus 2 grams/hour as a maintenance dose for the prevention of eclampsia in 62 pregnant and postpartum women with severe preeclampsia, 31 in each group. An intravenous loading dose of 6 grams of magnesium sulfate was administered over 30 minutes in both groups. The patients were then randomized to receive a maintenance dose of either 1 or 2 grams/hour for 24 hours. Primary outcomes consisted of serum magnesium levels at the following time points: baseline, 30 minutes, every 2 hours until the end of the first 6 hours, and every 6 hours thereafter until the termination of magnesium sulfate infusion. Side effects, maternal complications, and neonatal outcomes were the secondary outcomes.

RESULTS

Serum magnesium levels were higher in the 2-gram/hour group, with a statistically significant difference from 2 hours after the beginning of the magnesium sulfate infusion (P <.05). Oliguria was the most common complication recorded in both groups, with no significant difference between the 2 regimens (RR 0.88; 95% CI: 0.49-1.56; P = .65). No cases of eclampsia occurred. Side effects were more common in the 2-gram/hour group (RR 1.89; 95% CI: 1.04-3.41; P = .02); however, all were mild. There were no differences between the 2 groups regarding neonatal outcomes, except for admission to neonatal intensive care, which was more frequent in the 1-gram/hour group (25% vs 6.3%; P = .04).

CONCLUSION

Magnesium sulfate therapy at the maintenance dose of 1 gram/hour was just as effective as the 2-gram maintenance dose, with fewer side effects.

Alternative Magnesium Sulfate Dosing Regimens for Women With Preeclampsia: A Population Pharmacokinetic Exposure-Response Modeling and Simulation Study

Magnesium sulfate is the anticonvulsant of choice for eclampsia prophylaxis and treatment; however, the recommended dosing regimens are costly and cumbersome and can be administered only by skilled health professionals. The objectives of this study were to develop a robust exposure‐response model for the relationship between serum magnesium exposure and eclampsia using data from large studies of women with preeclampsia who received magnesium sulfate, and to predict eclampsia probabilities for standard and alternative (shorter treatment duration and/or fewer intramuscular injections) regimens. Exposure‐response modeling and simulation were applied to existing data. A total of 10 280 women with preeclampsia who received magnesium sulfate or placebo were evaluated. An existing population pharmacokinetic model was used to estimate individual serum magnesium exposure. Logistic regression was applied to quantify the serum magnesium area under the curve‐eclampsia rate relationship. Our exposure‐response model‐estimated eclampsia rates were comparable to observed rates. Several alternative regimens predicted magnesium peak concentration < 3.5 mmol/L (empiric safety threshold) and eclampsia rate ≤ 0.7% (observed response threshold), including 4 g intravenously plus 10 g intramuscularly followed by either 8 g intramuscularly every 6 hours × 3 doses or 10 g intramuscularly every 8 hours × 2 doses and 10 g intramuscularly every 8 hours × 3 doses. Several alternative magnesium sulfate regimens with comparable model‐predicted efficacy and safety were identified that merit evaluation in confirmatory clinical trials.

Population Pharmacokinetic Modeling to Evaluate Standard Magnesium Sulfate Treatments and Alternative Dosing Regimens for Women With Preeclampsia

Magnesium sulfate is the standard therapy for prevention and treatment of eclampsia. Two standard dosing regimens require either continuous intravenous infusion or frequent, large-volume intramuscular injections, which may preclude patients from receiving optimal care. This project sought to identify alternative, potentially more convenient, but similarly effective dosing regimens that could be used in restrictive clinical settings. A 2-compartment population pharmacokinetic (PK) model was developed to characterize serial PK data from 92 pregnant women with preeclampsia who received magnesium sulfate. Body weight and serum creatinine concentration had a significant impact on magnesium PK. The final PK model was used to simulate magnesium concentration profiles for the 2 standard regimens and several simplified alternative dosing regimens. The simulations suggest that intravenous regimens with loading doses of 8 g over 60 minutes followed by 2 g/h for 10 hours and 12 g over 120 minutes followed by 2 g/h for 8 hours (same total dose as the standard intravenous regimen but shorter treatment duration) would result in magnesium concentrations below the toxic range. For the intramuscular regimens, higher maintenance doses given less frequently (4 g intravenously + 10-g intramuscular loading doses with maintenance doses of 8 g every 6 hours or 10 g every 8 hours for 24 hours) or removal of the intravenous loading dose (eg, 10 g intramusculary every 8 hours for 24 hours) may be reasonable alternatives. In addition, individualized dose adjustments based on body weight and serum creatinine were proposed for the standard regimens.

A randomized trial comparing the pharmacology of magnesium sulfate when used to treat severe preeclampsia with serial intravenous boluses versus a continuous intravenous infusion

BACKGROUND

Magnesium sulfate is the preferred pharmacological intervention for the prevention and treatment of eclamptic seizures in pregnancy. Pain associated with intramuscular injections and the need for an electronic infusion pump for use intravenously represent significant barriers to broader utilization. We hypothesize that an alternative regimen based on serial intravenous (IV) boluses can produce serum concentrations comparable to those produced by a continuous infusion.

METHODS

An open-label randomized trial was performed at two hospitals in Egypt. Women with severe preeclampsia were eligible and enrolled between January 2015 and February 2016. Two hundred subjects were randomized by random numbers generated centrally in distinct blocks and stratified by study site. They were assigned to a continuous infusion arm, (4 g loading dose with 1 g/hr. continuous infusion) or a serial IV bolus arm, (6 g loading dose with 2 g bolus every 2 h using a Springfusor® pump). Sparsely sampled magnesium serum concentrations were collected, nonlinear mixed effect modeling was conducted and Monte Carlo simulations were used to generate 200 simulated subjects in each treatment arm. The simulated populations were used to determine area under the concentration-time curve (AUC) as a measure of total drug exposure and compared.

RESULTS

Simulated area under the magnesium serum concentration-time curve was significantly higher in the serial IV bolus arm than in the continuous infusion arm (1107 ± 461 mmol•min /L vs. 1010 ± 398 mmol•min /L, (P = 0.02)). Four percent of women in the serial bolus arm considered the treatment unacceptable or very unacceptable compared to 2% in the continuous infusion arm, (P = 0.68).

CONCLUSIONS

Serial IV boluses achieve serum magnesium concentrations statistically significantly higher but clinically comparable to those achieved with a continuous infusion and offer a third option for the administration of MgSO₄ to women with preeclampsia that may reduce barriers to utilization.

TRIAL REGISTRATION

Trial no. NCT02091401, March 17, 2014.

Obstetrician's risk perception on the prescription of magnesium sulfate in severe preeclampsia and eclampsia: A qualitative study in Brazil

Introduction

Magnesium sulfate (MgSO₄) is the drug of choice for the prevention and control of seizures in the management of severe preeclampsia/eclampsia. Several barriers have been identified in the use of MgSO₄, especially in low and middle-income settings.

Objective

To describe the obstetrician’s perception on possible reasons for underutilizing magnesium sulfate to treat preeclampsia/eclampsia.

Method

A qualitative clinical study, based on phenomenological reference by semi-structured interviews and open-ended discussions with obstetricians of the public healthcare system in primary care units (PCU) and referral maternity hospitals (RMH), in a southeastern Brazilian city.

Results

Fear of drug toxicity was the major cause for not prescribing the medication in PCU. Fear was justified by insufficient technical, structural and organizational resources of healthcare facilities and by a shortage of physicians properly trained for adequate drug use.

Conclusion

Fear of toxicity of magnesium sulfate was the main barrier towards timely and proper drug use. Periodic skill development and training of obstetricians, along with integration of the medical team in the work environment may contribute to decrease fear, ensuring safety of drug prescription and thus possibly reducing adverse outcomes related to PE.

Maternal administration of magnesium sulfate promotes cell proliferation in hippocampus dentate gyrus in offspring mice after exposing to prenatal stress

Prenatal stress (PS) inhibits cell proliferation in the hippocampal dentate gyrus (DG), which is related to hippocampal anatomy and function abnormality. The aim of the study was to investigate the effects of magnesium sulfate (MgSO₄) on PS-induced cell proliferation suppression in offspring during embryonic stage and postnatal spatial learning. MgSO₄ administration was performed after PS treatment on pregnant mice. Mice were randomly divided into four groups: non-PS or PS maternal mice injected with MgSO₄ or saline (P+NS, P+MG, C+MG and C+NS group). Corticosterone was collected from amniotic fluid of mother mice on day 17 of embryonic stage (E17). The ability for spatial learning and memory of pups postnatal 3 week was evaluated using water maze assay. Additionally, cell proliferation was detected by assessing the expression of Ki67 using immunohistochemistry in mice fetuses or pups. PS significantly increased corticosterone level in amniotic fluid (P<0.05) and impaired the spatial learning and memory (P+NS vs C+NS of latency time and track path length: P<0.05) of offspring on postnatal day 21. However, MgSO₄ administration could reverse PS-induced spatial learning and memory disability (P+MG vs P+NS, P<0.05). Additionally, PS reduced the number of Ki67-positive cell in hippocampal DG on E17, E19 and postnatal day 21 (P+NS vs C+NS, P<0.05), which were also abrogated by maternal administration of MgSO₄ (P+MG vs P+NS, P<0.05). Collectively, prenatal administration of MgSO₄ can reverse PS-induced reduction of cell proliferation in hippocampal DG during embryonic stage and postnatal spatial learning.

Clinical practice patterns on the use of magnesium sulphate for treatment of pre-eclampsia and eclampsia: a multi-country survey

Objective

To characterise the current clinical practice patterns regarding the use of magnesium sulphate (MgSO₄) for eclampsia prevention and treatment in a multi‐country network of health facilities and compare with international recommendations.

Design

Cross‐sectional survey.

Setting

A total of 147 health facilities in 15 countries across Africa, Latin America and Asia.

Population

Heads of obstetric departments or maternity units.

Methods

Anonymous online and paper‐based survey conducted in 2015.

Main outcome measures

Availability and use of MgSO₄; availability of a formal clinical protocol for MgSO₄ administration; and MgSO₄ dosing regimens for eclampsia prevention and treatment.

Results

Magnesium sulphate and a formal protocol for its administration were reported to be always available in 87.4% and 86.4% of all facilities, respectively. MgSO₄ was used for the treatment of mild pre‐eclampsia, severe pre‐eclampsia and eclampsia in 24.3%, 93.5% and 96.4% of all facilities, respectively. Regarding the treatment of severe pre‐eclampsia, 26.4% and 7.0% of all facilities reported using dosing regimens that were consistent with Zuspan and Pritchard regimens, respectively. Across regions, intramuscular maintenance regimens were more commonly used in the African region (45.7%) than in the Latin American (3.0%) and Asian (22.9%) regions, whereas intravenous maintenance regimens were more often used in the Latin American (94.0%) and Asian (60.0%) regions than in the African region (21.7%). Similar patterns were found for the treatment of eclampsia across regions.

Conclusions

The reported clinical use of MgSO₄ for eclampsia prevention and treatment varied widely, and was largely inconsistent with current international recommendations.

Tweetable abstract

MgSO₄ regimens for eclampsia prevention and treatment in many hospitals are inconsistent with international recommendations.

MgSO₄ regimens for eclampsia prevention and treatment in many hospitals are inconsistent with international recommendations.

Pharmacokinetics and placental transfer of magnesium sulfate in pregnant women

BACKGROUND

Magnesium sulfate is one of the most commonly prescribed intravenous medications in obstetrics. Despite its widespread use, there are limited data about magnesium pharmacokinetics, and magnesium is prescribed empirically without dose adjustment for different indications.

OBJECTIVE

The aim of this study was to characterize the pharmacokinetics and placental transfer of magnesium sulfate in pregnant women and to determine key covariates that impact the pharmacokinetics.

STUDY DESIGN

This is a prospective pharmacokinetic cohort study of pregnant women who were prescribed magnesium sulfate for preeclampsia, preterm labor, or extreme prematurity. Women received a 4-g loading dose and 2 g/h maintenance dose as clinically indicated. Maternal blood samples were obtained before and at multiple time points during and after magnesium administration. Cord blood also was sampled at delivery. A population pharmacokinetic approach that used a nonlinear mixed-effects modeling was used to characterize magnesium disposition.

RESULTS

Pharmacokinetic profiles of 111 pregnant women were analyzed. Magnesium clearance was 3.98 L/h in preeclamptic women and 5.88 L/h non-preeclamptic women. Steady-state concentration of magnesium was 7.2 mg/dL in preeclamptic women compared with 5.1 mg/dL in non-preeclamptic women. Maternal weight significantly impacted time to steady state. The ratio of the mean umbilical vein magnesium level to the mean maternal serum magnesium level at the time of delivery was 0.94 ± 0.15.

CONCLUSIONS

The study accurately characterizes the pharmacokinetics of magnesium administered to pregnant women. Preeclamptic status and maternal weight significantly impact serum magnesium levels. This pharmacokinetic model could be applied to larger cohorts to help tailor magnesium treatment and account for these covariates.

Clinical pharmacokinetic properties of magnesium sulphate in women with pre-eclampsia and eclampsia

BACKGROUND

The pharmacokinetic basis of magnesium sulphate (MgSO4 ) dosing regimens for eclampsia prophylaxis and treatment is not clearly established.

OBJECTIVES

To review available data on clinical pharmacokinetic properties of MgSO4 when used for women with pre-eclampsia and/or eclampsia.

SEARCH STRATEGY

MEDLINE, EMBASE, CINAHL, POPLINE, Global Health Library and reference lists of eligible studies.

SELECTION CRITERIA

All study types investigating pharmacokinetic properties of MgSO4 in women with pre-eclampsia and/or eclampsia.

DATA COLLECTION AND ANALYSIS

Two authors extracted data on basic pharmacokinetic parameters reflecting the different aspects of absorption, bioavailability, distribution and excretion of MgSO4 according to identified dosing regimens.

MAIN RESULTS

Twenty-eight studies investigating pharmacokinetic properties of 17 MgSO4 regimens met our inclusion criteria. Most women (91.5%) in the studies had pre-eclampsia. Baseline serum magnesium concentrations were consistently <1 mmol/l across studies. Intravenous loading dose between 4 and 6 g was associated with a doubling of this baseline concentration half an hour after injection. Maintenance infusion of 1 g/hour consistently produced concentrations well below 2 mmol/l, whereas maintenance infusion at 2 g/hour and the Pritchard intramuscular regimen had higher but inconsistent probability of producing concentrations between 2 and 3 mmol/l. Volume of distribution of magnesium varied (13.65-49.00 l) but the plasma clearance was fairly similar (4.28-5.00 l/hour) across populations.

CONCLUSION

The profiles of Zuspan and Pritchard regimens indicate that the minimum effective serum magnesium concentration for eclampsia prophylaxis is lower than the generally accepted level. Exposure-response studies to identify effective alternative dosing regimens should target concentrations achievable by these standard regimens.

TWEETABLE ABSTRACT

Minimum effective serum magnesium concentration for eclampsia prophylaxis is lower than the generally accepted therapeutic level.

Obstetric Pharmacokinetic Dosing Studies are Urgently Needed

Use of pharmacotherapy during pregnancy is common and increasing. Physiologic changes during pregnancy may significantly alter the overall systemic drug exposure, necessitating dose changes. A search of PubMed for pharmacokinetic clinical trials showed 494 publications during pregnancy out of 35,921 total pharmacokinetic published studies (1.29%), from the late 1960s through August 31, 2013. Closer examination of pharmacokinetic studies in pregnant women published since 2008 (81 studies) revealed that about a third of the trials were for treatment of acute labor and delivery issues, a third included studies of infectious disease treatment during pregnancy, and the remaining third were for varied ante-partum indications. Approximately, two-thirds of these recent studies were primarily funded by government agencies worldwide, one-quarter were supported by private non-profit foundations or combinations of government and private funding, and slightly <10% were supported by pharmaceutical industry. As highlighted in this review, vast gaps exist in pharmacology information and evidence for appropriate dosing of medications in pregnant women. This lack of knowledge and understanding of drug disposition throughout pregnancy place both the mother and the fetus at risk for avoidable therapeutic misadventures - suboptimal efficacy or excess toxicity - with medication use in pregnancy. Increased efforts to perform and support obstetric dosing and pharmacokinetic studies are greatly needed.