Changes in Enoxaparin Pharmacokinetics During Pregnancy and Implications for Antithrombotic Therapeutic Strategy

Venous Thromboembolism Prophylaxis in Obstetric Patients

Venous thromboembolism (VTE), including both pulmonary embolism (PE) and deep vein thrombosis (DVT), is the leading cause of maternal death in developed countries. Pregnancy is associated with an increased risk of VTE due to physiologic changes during the obstetric period that promote a hypercoagulable state. Appropriate use of prophylactic anticoagulants can decrease the event rate of thrombus formation in at-risk patients. In the United States, there is not a validated risk-assessment tool for VTE in obstetric patients or a clear consensus on initiation and optimal dosing strategy for the prophylactic use of anticoagulants. This article reviews the mechanism of coagulation disturbance that leads to an increased risk of VTE in obstetric patients, as well as the available literature surrounding pharmacologic prophylaxis.

Prophylactic Unfractionated Heparin in Antepartum Hospitalizations: A Randomized Controlled Trial

OBJECTIVE

To assess the effect of gestational age-based dosing of unfractionated heparin (UFH) compared with standard dosing of UFH for thromboprophylaxis on an elevated serum activated partial thromboplastin time (aPTT) during prolonged antepartum hospitalizations.

METHODS

This was a randomized trial of pregnant persons who were admitted in the antepartum period for at least 72 hours. Participants were randomly allocated to the standard dose of UFH (5,000 units subcutaneously every 12 hours) or the gestational age-based dose of UFH (first trimester [less than 14 weeks]: 5,000 units subcutaneously every 12 hours; second trimester [14-27 6/7 weeks]: 7,500 units subcutaneously every 12 hours; third trimester (28 weeks or more): 10,000 units subcutaneously every 12 hours). The primary outcome was the proportion of antepartum patients who had an elevated serum aPTT value above the normal range (more than 36.2 seconds) 6 hours after an UFH dose. Secondary outcomes included the development of venous thromboembolism (VTE) and reported side effects of heparin administration.

RESULTS

Between December 15, 2020, and April 1, 2022, 97 patients with antepartum hospitalizations were screened and 46 were randomized: 22 allocated to standard dosing and 24 allocated to gestational age-based dosing of UFH. A significantly greater proportion of antepartum patients who received gestational age-based dosing had an abnormal elevation in aPTT compared with those who received standard dosing (33.3% vs 4.8%, P =.02). Gestational age-based dosing resulted in higher maximum [interquartile range] aPTT (30.4 [27.4, 37.5] vs 26.6 [23.0, 29.6], P =.01) and anti-Xa levels (0.09 [0.09, 0.11] vs 0.09 [0.09, 0.09], P =.04). There was no significant difference in VTE between groups ( P =.47).

CONCLUSION

Gestational age-based dosing of UFH for thromboprophylaxis of antepartum hospitalizations was associated with significantly increased rates of elevated coagulation parameters compared with standard fixed dosing. This study suggests a need for close monitoring if higher doses of UFH during pregnancy are used later in gestation. The efficacy of gestational age-based dosing compared with standard dosing for UFH to prevent thromboembolic events remains an area for future investigation.

CLINICAL TRIAL REGISTRATION

ClinicalTrials.gov , NCT04635839.

The role of viscoelastic hemostatic assays for postpartum hemorrhage management and bedside intrapartum care

Viscoelastic hemostatic assays are point-of-care devices that assess coagulation and fibrinolysis in whole blood samples. These technologies provide numeric and visual information of clot initiation, clot strength, and clot lysis under low-shear conditions, and have been used in a variety of clinical settings and subpopulations, including trauma, cardiac surgery, and obstetrics. Emerging data indicate that these devices are useful for detecting important coagulation defects during major postpartum hemorrhage (especially low plasma fibrinogen concentration [hypofibrinogenemia]) and informing clinical decision-making for blood product use. Data from observational studies suggest that, compared with traditional formulaic approaches to transfusion management, targeted or goal-directed transfusion approaches using data from viscoelastic hemostatic assays are associated with reduced hemorrhage-related morbidity and lower blood product requirement. Viscoelastic hemostatic assays can also be used to identify and treat coagulation defects in patients with inherited or acquired coagulation disorders, such as factor XI deficiency or immune-mediated thrombocytopenia, and to assess hemostatic profiles of patients prescribed anticoagulant medications to mitigate the risk of epidural hematoma after neuraxial anesthesia and postpartum hemorrhage after delivery.

Effects of anti-Xa activity monitoring on the outcome of high-risk pregnancies treated with a prophylactic dose of low-molecular-weight heparin

OBJECTIVE

To evaluate if anti-Xa level monitoring and dose adjustment in women using a prophylactic dose of enoxaparin can decrease placenta-mediated pregnancy complications.

METHODS

This retrospective observational cohort study included pregnant women receiving enoxaparin prophylaxis, who were followed at the Thrombosis and Hemostasis Outpatient clinic between 2010 and 2017. The dose was adjusted according to enoxaparin anti-Xa levels in the study group or the weight of individuals in the control group.

RESULTS

Of 585 women surveyed, 110 met the inclusion criteria; 63 of them were included in the study group and 47 in the control group. Mean starting dose was 46 versus 43 mg (p = .25), mean final dose was 52 mg versus 45 mg (p = .03) and dose adjustment was required in 37% versus 11% (p = .002) in the study and control groups, respectively. Twenty-eight percent of anti-Xa measurements in the second trimester were beneath the prophylactic threshold, compared to 11% and 16% in the first and third trimesters, respectively (p = .02). Labors ended with live birth in 91% versus 94% of cases (p = .5), 85% versus 68% of pregnancies were term (p = .05), 11% versus 23% of newborns were low birth weight (p = .1) and placenta-mediated pregnancy complications were documented in 9% versus 19%, (p = .17) in the study group relative to controls, respectively.

CONCLUSIONS

The most prominent decrease in anti-Xa levels was observed in the second trimester. Monitored women had significantly more term deliveries and demonstrated a trend toward higher birth weight and fewer placenta-mediated pregnancy complications. Larger studies are needed to confirm improved pregnancy outcome in monitored women.

Physiologic Changes During Pregnancy and Impact on Small-Molecule Drugs, Biologic (Monoclonal Antibody) Disposition, and Response

Pregnancy is a unique physiological state that results in many changes in bodily function, including cellular, metabolic, and hormonal changes. These changes can have a significant impact on the way small-molecule drugs and monoclonal antibodies (biologics) function and are metabolized, including efficacy, safety, potency, and adverse effects. In this article, we review the various physiologic changes that occur during pregnancy and their effects on drug and biologic metabolism, including changes in the coagulation, gastrointestinal, renal, endocrine, hepatic, respiratory, and cardiovascular systems. Additionally, we discuss how these changes can affect the processes of drug and biologic absorption, distribution, metabolism, and elimination (pharmacokinetics), and how drugs and biologics interact with biological systems, including mechanisms of drug action and effect (pharmacodynamics) during pregnancy, as well as the potential for drug-induced toxicity and adverse effects in the mother and developing fetus. The article also examines the implications of these changes for the use of drugs and biologics during pregnancy, including consequences of suboptimal plasma drug concentrations, effect of pregnancy on the pharmacokinetics and pharmacodynamics of biologics, and the need for careful monitoring and individualized drug dosing. Overall, this article aims to provide a comprehensive understanding of the physiologic changes during pregnancy and their effects on drug and biologic metabolism to improve the safe and effective use of drugs.

Pharmacokinetic Evaluation in Pregnancy-Current Status and Future Considerations: Workshop Summary

As pregnant individuals have traditionally been excluded from clinical trials, there is a gap in knowledge at the time of drug approval regarding safety, efficacy, and appropriate dosing for most prescription medications used during pregnancy. Physiologic changes in pregnancy can result in changes in pharmacokinetics that can impact safety or efficacy. This highlights the need to foster further research and collection of pharmacokinetic data in pregnancy to ensure appropriate drug dosing in pregnant individuals. Therefore, the US Food and Drug Administration and the University of Maryland Center of Excellence in Regulatory Science and Innovation hosted a workshop on May 16 and 17, 2022, titled "Pharmacokinetic Evaluation in Pregnancy." This is a summary of the workshop proceedings.

Assessment of the Particularities of Thrombophilia in the Management of Pregnant Women in the Western Part of Romania

Background and objectives: Thrombophilia in pregnant women is a condition whose incidence is constantly increasing worldwide, and, under these conditions, the development of preventive procedures is becoming essential. In this study, we aimed to evaluate thrombophilia in pregnant women in the western part of Romania and to establish anthropometric characteristics, socioeconomic features, and genetic and risk factors. Material and Methods: 178 pregnant women were divided into three study groups, according to the type of thrombophilia, aiming to carry out the genetic profile and the acquired one. Anthropometric measures and biological tests were performed. Results: The mixed type of thrombophilia predominates. The particularities of pregnant women diagnosed with thrombophilia are higher age, living in an urban environment, with normal BMI, approximately 36 weeks of gestational period, and having at least one miscarriage. Regarding the most frequent thrombophilic genetic markers, we obtained the MTFHR gene mutation C677T and A1298C, followed by the PAI-1 4G/5G gene mutation. Smoking represents an aggravating factor in the evolution of this pathology, manifested through the increase of D-dimers and the decrease in antithrombin values, simultaneously with the increase in therapeutic need. Conclusions: The predominance of MTHFR and PAI-1 4G/5G gene polymorphism is a particularity of pregnant women with thrombophilia from the western part of Romania. Smoking is confirmed as an important risk factor in spontaneous abortion.

How can Secondary Thromboprophylaxis in High-Risk Pregnant Patients be Improved?

Low-molecular-weight heparin (LMWH) is suggested for thromboprophylaxis in pregnant women with previous venous thromboembolism (VTE). Anyway, there is only limited amount of studies evaluating the effect of LMWH on hemostatic parameters during pregnancy of patients with previous VTE and the need of secondary thromboprophylaxis. We therefore provide results of prospective and longitudinal assessment of changes in hemostasis in high-risk pregnant women at four times during pregnancy (T1–T4) and one time after the postpartum period (T5) used for individualized modification of thromboprophylaxis. In this study, the results of coagulation factor VIII (FVIII) and protein S (PS) activity, ProC Global ratio and anti-Xa activity were evaluated. Despite the thromboprophylaxis, an increased predisposition to thromboembolic complications was detected (significant increase in FVIII activity and decrease in PS function, ProC Global ratio not normalized even after the postpartum period – p < .0001 between controls and T5 for PS and ProC Global). These results indicate that hemostasis may not be restored even 6 to 8 weeks after delivery and pose the question when is it safe to withdraw the anticoagulant thromboprophylaxis in high-risk patients with prior VTE.

Regional anaesthesia in patients on antithrombotic drugs: Joint ESAIC/ESRA guidelines

BACKGROUND

Bleeding is a potential complication after neuraxial and peripheral nerve blocks. The risk is increased in patients on antiplatelet and anticoagulant drugs. This joint guideline from the European Society of Anaesthesiology and Intensive Care and the European Society of Regional Anaesthesia aims to provide an evidence-based set of recommendations and suggestions on how to reduce the risk of antithrombotic drug-induced haematoma formation related to the practice of regional anaesthesia and analgesia.

DESIGN

A systematic literature search was performed, examining seven drug comparators and 10 types of clinical intervention with the outcome being peripheral and neuraxial haematoma. Grading of Recommendations, Assessment, Development and Evaluation (GRADE) was used for assessing the methodological quality of the included studies and for formulating recommendations. A Delphi process was used to prepare a clinical practice guideline.

RESULTS

Clinical studies were limited in number and quality and the certainty of evidence was assessed to be GRADE C throughout. Forty clinical practice statements were formulated. Using the Delphi-process, strong consensus (>90% agreement) was achieved in 57.5% of recommendations and consensus (75 to 90% agreement) in 42.5%.

DISCUSSION

Specific time intervals should be observed concerning the adminstration of antithrombotic drugs both prior to, and after, neuraxial procedures or those peripheral nerve blocks with higher bleeding risk (deep, noncompressible). These time intervals vary according to the type and dose of anticoagulant drugs, renal function and whether a traumatic puncture has occured. Drug measurements may be used to guide certain time intervals, whilst specific reversal for vitamin K antagonists and dabigatran may also influence these. Ultrasound guidance, drug combinations and bleeding risk scores do not modify the time intervals. In peripheral nerve blocks with low bleeding risk (superficial, compressible), these time intervals do not apply.

CONCLUSION

In patients taking antiplatelet or anticoagulant medications, practitioners must consider the bleeding risk both before and after nerve blockade and during insertion or removal of a catheter. Healthcare teams managing such patients must be aware of the risk and be competent in detecting and managing any possible haematomas.

Prevention and management of venous thromboembolism in pregnancy: cutting through the practice variation

There is clinical practice variation in the area of prevention and management of venous thromboembolism (VTE) in pregnancy. There are limited data and differing recommendations across major clinical practice guidelines, especially relating to the role of postpartum low-molecular-weight heparin (LMWH) for patients with mild inherited thrombophilia and those with pregnancy-related VTE risk factors. This chapter explores the issues of practice variation and related data for postpartum VTE prevention. Controversial topics of VTE management in pregnancy are also reviewed and include LMWH dosing and the role of anti-Xa level monitoring, as well as peripartum anticoagulation management around labor and delivery.

An update on the physiologic changes during pregnancy and their impact on drug pharmacokinetics and pharmacogenomics

For many years, the medical community has relied in clinical practice on historic data about the physiological changes that occur during pregnancy. However, some newer studies have disputed a number of assumptions in these data for not being evidence-based or derived from large prospective cohort-studies. Accurate knowledge of these physiological changes is important for three reasons: Firstly, it facilitates correct diagnosis of diseases during pregnancy; secondly, it enables us to answer questions about the effects of medication during pregnancy and the ways in which pregnancy alters pharmacokinetic and drug-effects; and thirdly, it allows for proper modeling of physiologically-based pharmacokinetic models, which are increasingly used to predict gestation-specific changes and drug-drug interactions, as well as develop new knowledge on the mode-of-action of drugs, the mechanisms underlying their interactions, and any adverse effects following drug exposure. This paper reviews new evidence regarding the physiologic changes during pregnancy in relation to existing knowledge.

Model-Informed Dose Optimization in Pregnancy

Pregnancy is associated with several physiological changes that can alter the pharmacokinetics (PK) and pharmacodynamics of drugs. These may require dosing changes in pregnant women to achieve drug exposures comparable to the nonpregnant population. There is, however, limited information available on the PK and pharmacodynamics of drugs used during pregnancy. Practical difficulties in performing PK studies and potential liability issues are often the reasons for the availability of limited information. Over the past several years, there has been a rapid development in the application of various modeling strategies such as population PK and physiologically based PK modeling to provide guidance on drug dosing in this special patient population. Population PK models rely on measured PK data, whereas physiologically based PK models integrate physiological, preclinical, and clinical data to quantify changes in PK of drugs in various patient populations. These modeling strategies offer a promising approach to identify the drugs with PK changes during pregnancy and guide dose adjustment in pregnant women. This review focuses on PBPK modeling to guide drug therpay in pregnancy.

Low Molecular Weight Heparins (LMWH) and Implications along Pregnancy: a Focus on the Placenta

Low molecular weight heparins (LMWH) have been largely studied for their use during pregnancy. The biology and the pharmacology of these molecules are well known and may be summarized in three main mechanisms of action: anti-coagulant, anti-inflammatory, and immunomodulant. The clinical implications of these drugs during pregnancy are mainly related to their action on the placenta, because of the presence of specific molecular and cellular targets, particularly at the trophoblast-endometrial interface. As well as for the prevention and treatment of thromboembolism, LMWH have been largely investigated for the improvement of embryo implantation and for the prevention of placenta-related complications such as preeclampsia, fetal growth restriction, and intrauterine fetal death. However, data on this topic are still unclear. The present review discusses the biological features, the mechanisms of action, and the possible contribution of LMWH to the success of placentation along pregnancy, pointing out the need for future basic science and clinical researches in this important field with the final aim to improve clinical practice in high-risk pregnancies.

Anti-Xa Monitoring of Low-Molecular-Weight Heparin during Pregnancy: A Systematic Review

Low-molecular-weight heparin (LMWH) is commonly used for preventing or treating venous thromboembolic disease (VTE) during pregnancy. The physiological changes in maternal metabolism have led to discussions on optimal LMWH dosing strategy and possible need for monitoring. The aim of this systematic review is to summarize and discuss whether LMWH dose adjustment according to anti-Xa provides superior effectiveness and safety compared with weight adjusted or fixed dosed LMWH in pregnant women. A systematic literature search was performed in PubMed, Embase, and Scopus on September 26, 2020. The study is reported according to Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Effectiveness was defined as episodes of thrombosis and safety as bleeding episodes. In total, 33 studies were included: 4 randomized controlled studies and 29 cohort studies. Prophylactic dosing strategies employing weight dosed, fixed dosed, or anti-Xa adjusted LMWH dosing performed equal in effectiveness and safety. In pregnant women with VTE or high thromboembolic risk, therapeutic weight-adjusted LMWH and weight plus anti-Xa-adjusted LMWH provided equal results in terms of effectiveness and safety. Pregnant women with mechanical heart valves (MHVs) received therapeutic anti-Xa-adjusted LMWH with four out of seven studies presenting mean peak anti-Xa within target ranges. Still, pregnant women with MHV experienced both thrombosis and bleeding with anti-Xa in target. Based on the results of this systematic review, current evidence does not support the need for anti-Xa monitoring when using LMWH as thromboprophylaxis or treatment during pregnancy. Nonetheless, the need for anti-Xa monitoring in pregnant women with MHV may need further scrutiny.

Prophylactic Anticoagulation With Intermediate-Dose Certoparin in Vascular-Risk Pregnancies-The PACER-VARP Registry

The management of pregnant women at increased risk of thromboembolic/other vascular events is still a matter of debate. In a single-center, retrospective, observational trial, we analyzed the safety and efficacy of prophylactic anticoagulation with certoparin in pregnant women at intermediate- or high-risk by EThIG criteria of thromboembolic/other vascular events. Subcutaneous certoparin 8,000 IU once daily was administered immediately after pregnancy confirmation and continued for 6 weeks postpartum. We investigated 74 pregnancies (49 women; mean age 31.8 years; weight 77.3 kg). Most prevalent risk factors were factor V Leiden mutation (40.5%), thrombogenic factor II mutation (12.2%) and protein S deficiency (8.1%). In 76 control pregnancies prior to registry inclusion/without anticoagulation there were 14 cases [18.4%] of venous thromboembolism (between week 7 gestation and week 8 postpartum); 63.2% pregnancies resulted in abortion (median week 8.6 gestation). With certoparin anticoagulation, thromboembolism was 1.4%, exclusively non-major bleeding was 4.1% and abortion was 10.8%. One case of pre-eclampsia necessitating obstetric intervention occurred. Prophylactic anticoagulation with intermediate-dose certoparin throughout pregnancies at increased venous vascular risk was safe and effective.

[SBA 2020: Regional anesthesia guideline for using anticoagulants update]

The development of protocols to prevent perioperative Venous Thromboembolism (VTE) and the introduction of increasingly potent antithrombotic drugs have resulted in concerns of increased risk of neuraxial bleeding. Since the Brazilian Society of Anesthesiology (SBA) 2014 guideline, new oral anticoagulant drugs were approved by international regulating agencies, and by ANVISA. Societies and organizations that try to approach concerns through guidelines have presented conflicting perioperative management recommendations. As a response to these issues and to the need for a more rational approach, managements were updated in the present narrative revision, and guideline statements made. They were projected to encourage safe and quality patient care, but cannot assure specific results. Like any clinical guide recommendation, they are subject to review as knowledge grows, on specific complications, for example. The objective was to assess safety aspects of regional analgesia and anesthesia in patients using antithrombotic drugs, such as: possible technique-associated complications; spinal hematoma-associated risk factors, prevention strategies, diagnosis and treatment; safe interval for discontinuing and reinitiating medication after regional blockade.

ACOG Practice Bulletin No. 196: Thromboembolism in Pregnancy

Women who are pregnant or in the postpartum period have a fourfold to fivefold increased risk of thromboembolism compared with nonpregnant women (). Approximately 80% of thromboembolic events in pregnancy are venous (), with a prevalence of 0.5-2.0 per 1,000 pregnant women (). Venous thromboembolism (VTE) is one of the leading causes of maternal mortality in the United States, accounting for 9.3% of all maternal deaths ().The prevalence and severity of this condition during pregnancy and the peripartum period warrant special consideration of management and therapy. Such therapy includes the treatment of acute thrombotic events and prophylaxis for those at increased risk of thrombotic events. The purpose of this document is to provide information regarding the risk factors, diagnosis, management, and prevention of thromboembolism, particularly VTE in pregnancy. This Practice Bulletin has been revised to reflect updated guidance regarding screening for thromboembolism risk and management of anticoagulation around the time of delivery.

Follow-up and management of valvular heart disease patients with prosthetic valve: a clinical practice guideline for Indian scenario

PURPOSE

Valvular heart disease (VHD) patients after prosthetic valve implantation are at risk of thromboembolic events. Follow-up care of patients with prosthetic valve has a paramount role in reducing the morbidity and mortality. Currently, in India, there is quintessential need to stream line the follow-up care of prosthetic valve patients. This mandates the development of a consensus guideline for the antithrombotic therapy in VHD patients post prosthetic valve implantation.

METHODS

A national level panel was constituted comprising 13 leading cardio care experts in India who thoroughly reviewed the up to date literature, formulated the recommendations, and developed the consensus document. Later on, extensive discussions were held on this draft and the recommendations in 8 regional meetings involving 79 additional experts from the cardio care in India, to arrive at a consensus. The final consensus document is developed relying on the available evidence and/or majority consensus from all the meetings.

RESULTS

The panel recommended vitamin K antagonist (VKA) therapy with individualized target international normalized ratio (INR) in VHD patients after prosthetic valve implantation. The panel opined that management of prosthetic valve complications should be personalized on the basis of type of complications. In addition, the panel recommends to distinguish individuals with various co-morbidities and attend them appropriately.

CONCLUSIONS

Anticoagulant therapy with VKA seems to be an effective option post prosthetic valve implantation in VHD patients. However, the role for non-VKA oral therapy in prosthetic valve patients and the safety and efficacy of novel oral anticoagulants in patients with bioprosthetic valve need to be studied extensively.

Pearls in clinical obstetrics: challenges in anticoagulation in pregnancy

Women are at increased risk for venous thromboembolism (VTE) during both pregnancy and in the post-partum period. We have conducted a comprehensive literature review of the use of anticoagulation in pregnancy for pregnant women at increased risk for VTE. Multiple factors, including physiologic and pharmacokinetic changes make the treatment and prevention of VTE complicated in pregnancy. Adequate treatment and prevention of VTE in pregnancy is critically important, yet good quality medical studies continue to be lacking. There is a growing amount of data for the use of low molecular weight heparin (LMWH) in pregnant women and this remains the treatment of choice in most indications. For both prophylactic and therapeutic treatments, when LMWHs are chosen, monitoring of antifactor Xa level, although controversial, is advised. Women with prosthetic valve who become pregnant face challenges in regard of type of anticoagulation, dosing and monitoring during pregnancy. Delivery options and peripartum care should be defined with a multidisciplinary approach and taking patient's preference and autonomy in consideration. More high-quality research on this topic is needed to guide the clinical care of this unique population.

Clinical 'Pearls' of maternal critical care: part I

PURPOSE OF REVIEW

This review outlines the challenges in looking after pregnant women with thromboembolism and sepsis who either become or are at risk of becoming critically ill during pregnancy.

RECENT FINDINGS

The Pregnancy Mortality Surveillance systems in both the USA and UK record the most common causes of maternal death as thromboembolism and sepsis. Both of these conditions have improved outcomes with timely maternal critical care provided by a multidisciplinary team.

SUMMARY

In this review, we discuss the pathophysiology, diagnosis, and management of thromboembolism and sepsis, two very important conditions with high mortality requiring admission to intensive care.

Preventing venous thromboembolism during pregnancy and postpartum: crossing the threshold

When should a patient with a known thrombophilia or prior venous thromboembolism (VTE) receive low-molecular-weight heparin (LMWH) prophylaxis during pregnancy and/or the postpartum period? Accurately predicting thrombotic and bleeding risks and knowing what to do with this information is at the heart of decision-making in these challenging scenarios. This article will explore the concept of a risk threshold from clinician and patient perspectives and provide guidance for the use of antepartum and postpartum LMWH prophylaxis in women with a known thrombophilia or prior VTE. Advice for the management of LMWH prophylaxis use around labor and delivery is also reviewed.

A case that illustrates the challenges of managing pregnant patients with antithrombin deficiency: More questions than answers

Using an illustrative case of a patient with antithrombin (AT) deficiency who developed a recurrent venous thromboembolism (VTE) in pregnancy despite therapeutic low-molecular-weight heparin (LMWH), we highlight what is known in the literature and address areas of controversy through a series of questions around the case. The questions we address include the role of anti-Xa monitoring for patients with past VTE on antepartum LMWH, what treatment regimen is recommended for pregnant patients who develop a recurrent VTE while on therapeutic anticoagulation, the role of antepartum AT concentrate prophylaxis, and the management of labor/delivery, epidural anesthesia and postpartum anticoagulation. We also describe practical considerations for use of AT concentrate, including teaching our patient to self-infuse AT concentrate at home with support of a hemophilia treatment center (HTC), and the direct and indirect costs of AT concentrate for secondary prophylaxis.

Pregnancy-Associated Changes in Pharmacokinetics: A Systematic Review

BACKGROUND

Women are commonly prescribed a variety of medications during pregnancy. As most organ systems are affected by the substantial anatomical and physiological changes that occur during pregnancy, it is expected that pharmacokinetics (PK) (absorption, distribution, metabolism, and excretion of drugs) would also be affected in ways that may necessitate changes in dosing schedules. The objective of this study was to systematically identify existing clinically relevant evidence on PK changes during pregnancy.

METHODS AND FINDINGS

Systematic searches were conducted in MEDLINE (Ovid), Embase (Ovid), Cochrane Central Register of Controlled Trials (Ovid), and Web of Science (Thomson Reuters), from database inception to August 31, 2015. An update of the search from September 1, 2015, to May 20, 2016, was performed, and relevant data were added to the present review. No language or date restrictions were applied. All publications of clinical PK studies involving a group of pregnant women with a comparison to nonpregnant participants or nonpregnant population data were eligible to be included in this review. A total of 198 studies involving 121 different medications fulfilled the inclusion criteria. In these studies, commonly investigated drug classes included antiretrovirals (54 studies), antiepileptic drugs (27 studies), antibiotics (23 studies), antimalarial drugs (22 studies), and cardiovascular drugs (17 studies). Overall, pregnancy-associated changes in PK parameters were often observed as consistent findings among many studies, particularly enhanced drug elimination and decreased exposure to total drugs (bound and unbound to plasma proteins) at a given dose. However, associated alterations in clinical responses and outcomes, or lack thereof, remain largely unknown.

CONCLUSION

This systematic review of pregnancy-associated PK changes identifies a significant gap between the accumulating knowledge of PK changes in pregnant women and our understanding of their clinical impact for both mother and fetus. It is essential for clinicians to be aware of these unique pregnancy-related changes in PK, and to critically examine their clinical implications.

What do we learn from repeated population analyses?

Population analyses are performed on new and existing drugs. They play an important role in quantifying the time course of drug effects and provide a means of understanding the impact of variability between individuals on dosing requirements. For some drugs there have been several population analyses reported in the literature. It is important to understand how repeated population analyses can value add and what authors and readers can consider when reviewing such analyses. The purpose of this review is to explore what is learnt from repeated population analyses and provide an understanding of how the value-added nature of these analyses can be considered.

Pregnancy-induced changes in the pharmacokinetics of caffeine and its metabolites

This study sought to assess the pharmacokinetic (PK) changes of caffeine and its CYP1A2 metabolites across the 3 trimesters of pregnancy. A prospective, multicenter PK study was conducted among 59 pregnant women (93.2% white) who were studied once during a trimester. One beverage with 30-95 mg caffeine was consumed, and a blood/urine sample was collected within 1 hour postingestion. Concentrations of caffeine and its primary metabolites were quantified from serum and urine by LC-MS/MS. There was a significant increase in dose-normalized caffeine serum and urine concentrations between the first and third trimesters (P < .05 and P < .01, respectively). Normalized theophylline concentrations also increased significantly in the third trimester in serum (P < .001) and in urine (P < .05). The caffeine urine/serum concentration ratio also increased in the last trimester (P < .05). No significant difference was found in normalized paraxanthine or theobromine concentrations. This study identified decreased caffeine metabolism and an increase in the active metabolite theophylline concentrations during pregnancy, especially in the third trimester, revealing evidence of the large role that pregnancy plays in influencing caffeine metabolism.

Use and impact of cardiac medication during pregnancy

ABSTRACT 

Cardiovascular disease is the most encountered cause of maternal death during pregnancy in the western world and an increase in maternal mortality due to cardiac causes has been observed. More women with congenital or acquired heart disease have the desire to become pregnant. Pregnancy is known to impose a major hemodynamic burden and also has impacts on the coagulation system. The risk of developing complications is clearly increased as compared with the normal population. For optimal management, it is crucial to have information on the effects of cardiac medications on the fetus. The focus of this article is to discuss the management of cardiac disease in pregnancy, as well as the known safety of cardiac medications for the mother and/or fetus.

Guidelines for the prevention of stroke in patients with stroke and transient ischemic attack: a guideline for healthcare professionals from the American Heart Association/American Stroke Association

The aim of this updated guideline is to provide comprehensive and timely evidence-based recommendations on the prevention of future stroke among survivors of ischemic stroke or transient ischemic attack. The guideline is addressed to all clinicians who manage secondary prevention for these patients. Evidence-based recommendations are provided for control of risk factors, intervention for vascular obstruction, antithrombotic therapy for cardioembolism, and antiplatelet therapy for noncardioembolic stroke. Recommendations are also provided for the prevention of recurrent stroke in a variety of specific circumstances, including aortic arch atherosclerosis, arterial dissection, patent foramen ovale, hyperhomocysteinemia, hypercoagulable states, antiphospholipid antibody syndrome, sickle cell disease, cerebral venous sinus thrombosis, and pregnancy. Special sections address use of antithrombotic and anticoagulation therapy after an intracranial hemorrhage and implementation of guidelines.

Management of cardiovascular diseases during pregnancy

The prevalence of cardiovascular diseases (CVDs) in women of childbearing age is rising. The successes in medical and surgical treatment of congenital heart disease have led to an increasing number of women at childbearing age presenting with problems of treated congenital heart disease. Furthermore, in developing countries and in immigrants from these countries, rheumatic valvular heart disease still plays a significant role in young women. Increasing age of pregnant women and increasing prevalence of atherosclerotic risk factors have led to an increase in women with coronary artery disease at pregnancy. Successful management of pregnancy in women with CVDs requires early diagnosis, a thorough risk stratification, and appropriate management by a multidisciplinary team of obstetricians, cardiologists, anesthesiologists, and primary care physicians. The following review is based on the recent European guidelines on the management of CVDs during pregnancy, which aim at providing concise and simple recommendations for these challenging problems.

Semiphysiological versus empirical modelling of the population pharmacokinetics of free and total cefazolin during pregnancy

This work describes a first population pharmacokinetic (PK) model for free and total cefazolin during pregnancy, which can be used for dose regimen optimization. Secondly, analysis of PK studies in pregnant patients is challenging due to study design limitations. We therefore developed a semiphysiological modeling approach, which leveraged gestation-induced changes in creatinine clearance (CrCL) into a population PK model. This model was then compared to the conventional empirical covariate model. First, a base two-compartmental PK model with a linear protein binding was developed. The empirical covariate model for gestational changes consisted of a linear relationship between CL and gestational age. The semiphysiological model was based on the base population PK model and a separately developed mixed-effect model for gestation-induced change in CrCL. Estimates for baseline clearance (CL) were 0.119 L/min (RSE 58%) and 0.142 L/min (RSE 44%) for the empirical and semiphysiological models, respectively. Both models described the available PK data comparably well. However, as the semiphysiological model was based on prior knowledge of gestation-induced changes in renal function, this model may have improved predictive performance. This work demonstrates how a hybrid semiphysiological population PK approach may be of relevance in order to derive more informative inferences.

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.

Population Pharmacokinetics of Enoxaparin During the Antenatal Period

Background—

The optimal dosing strategy of low-molecular-weight heparins for the treatment of antenatal venous thromboembolism is not known. The physiological changes associated with pregnancy alter the pharmacokinetic profile of low-molecular-weight heparins, which has led to controversy and subsequent variation in practice, when pregnant women with venous thromboembolism are treated with low-molecular-weight heparins. Our objective was to develop a robust pharmacokinetic model of enoxaparin during the antenatal period to address this problem.

Method and Results—

Women prescribed antenatal enoxaparin were eligible to enroll in the study. Recruited women were reviewed monthly and had up to 3 anti-Xa activities (trough and 1 and 3 hours after dose) drawn at each clinic attendance. Compartmental pharmacokinetic modeling was conducted using nonlinear mixed-effects modeling. One hundred twenty-three patients contributed 795 anti-Xa activities for pharmacokinetic modeling purposes. Both enoxaparin clearance and volume of distribution were increased during pregnancy. Simulations of once- versus twice-daily enoxaparin administration demonstrated that both dosing regimens would reach target 3-hour plasma concentrations throughout the duration of the pregnancy. When trough anti-Xa activity was simulated, both once- and twice-daily regimens exhibited an increase in trough anti-Xa activity with the progression of pregnancy. This is explained by the significant increase in volume of distribution observed during pregnancy.

Conclusions—

The half-life of enoxaparin is prolonged with the progression of pregnancy, and our work provides compelling evidence for prescribing once-daily enoxaparin for the treatment of antenatal venous thromboembolism. National and international guideline recommendations should be reconsidered.

Peak plasma anti-Xa levels after first and third doses of enoxaparin in women receiving weight-based thromboprophylaxis following caesarean section: a prospective cohort study

BACKGROUND

Women undergoing caesarean section are at higher risk for thromboembolic complications following delivery than other parturients. The aim of this study was to determine whether higher doses of enoxaparin based on body weight are safe and more likely to achieve plasma anti-Xa levels within the accepted thromboprophylactic range.

METHODS

We undertook a prospective cohort study of 80 women undergoing caesarean section in a tertiary obstetric hospital with >6000 deliveries per year. Enoxaparin was administered after caesarean section using the Royal College of Obstetricians and Gynaecologists weight-adjusted dosing guidelines. Plasma anti-Xa levels were measured at baseline and 3-4 h after enoxaparin administration on days one and three postoperatively. The main outcomes of interest were plasma anti-Xa levels and the proportion of patients with plasma anti-Xa levels in the range of 0.2-0.4 IU/mL.

RESULTS

The proportion of women with anti-Xa levels between 0.2 and 0.4 IU/mL was 72% (95% CI 60-81%). Unadjusted mean anti-Xa levels were 0.26 ± 0.09 IU/mL and 0.28 ± 0.08 IU/mL on day one and day three respectively. No woman had levels >0.48 IU/mL.

CONCLUSION

The majority of women receiving weight-based enoxaparin thromboprophylaxis following caesarean section achieved plasma anti-Xa levels within the putative thromboprophylactic range. No woman achieved levels associated with an increased risk of bleeding (>0.8 IU/mL). These findings provide a safety basis for a large prospective study using this regimen.