Being precise with anticoagulation to reduce adverse drug reactions: are we there yet?

Anticoagulants are potent therapeutics widely used in medical and surgical settings, and the amount spent on anticoagulation is rising. Although warfarin remains a widely prescribed oral anticoagulant, prescriptions of direct oral anticoagulants (DOACs) have increased rapidly. Heparin-based parenteral anticoagulants include both unfractionated and low molecular weight heparins (LMWHs). In clinical practice, anticoagulants are generally well tolerated, although interindividual variability in response is apparent. This variability in anticoagulant response can lead to serious incident thrombosis, haemorrhage and off-target adverse reactions such as heparin-induced thrombocytopaenia (HIT). This review seeks to highlight the genetic, environmental and clinical factors associated with variability in anticoagulant response, and review the current evidence base for tailoring the drug, dose, and/or monitoring decisions to identified patient subgroups to improve anticoagulant safety. Areas that would benefit from further research are also identified. Validated variants in VKORC1, CYP2C9 and CYP4F2 constitute biomarkers for differential warfarin response and genotype-informed warfarin dosing has been shown to reduce adverse clinical events. Polymorphisms in CES1 appear relevant to dabigatran exposure but the genetic studies focusing on clinical outcomes such as bleeding are sparse. The influence of body weight on LMWH response merits further attention, as does the relationship between anti-Xa levels and clinical outcomes. Ultimately, safe and effective anticoagulation requires both a deeper parsing of factors contributing to variable response, and further prospective studies to determine optimal therapeutic strategies in identified higher risk subgroups.

Anti-Factor Xa Levels in Low-weight Surgical Patients Receiving Enoxaparin for Venous Thromboembolism Prophylaxis: A Prospective Cohort Study

Enoxaparin is indicated for thromboprophylaxis in non-orthopedic surgical patients at a fixed dose of 40 mg daily. According to the US Food and Drug Administration’s enoxaparin prescribing information, this dose exposes low-weight patients (males < 57 kg, females < 45 kg) to a higher risk of bleeding. This study aimed to determine the rate of achieving a prophylactic peak anti-factor Xa (AFXa) level in low-weight surgical patients using enoxaparin 30 mg daily. Low-weight patients admitted for abdominopelvic or noncardiac thoracic surgery from May 2018 to May 2019 were prospectively studied. After receiving daily enoxaparin 30 mg, peak AFXa levels were assessed for achieving a prophylactic level (0.2-0.5 IU/mL). In 121 patients, the proportion of achieving a prophylactic peak AFXa level was 66.1%. More females (84.8%) achieved a prophylactic level compared to males (54.7%, P = .001). All out-of-range peak AFXa levels (33.9%) were sub-prophylactic. The median peak AFXa level was lower in males (0.24 [0.1-0.47] IU/mL) than females (0.31 [0.1-0.5] IU/mL; P < .001). On univariate analysis, female sex and weight were associated with achieving a prophylactic peak AFXa level. On multivariate analysis, only female sex was independently associated with an adequate prophylactic AFXa level (odds ratio 3.17, 95% CI: 1.32-11.94; P = .014). Four venous thromboembolism events (3.3%) were observed in patients with sub-prophylactic peak AFXa levels (9.7%). Two-thirds of low-weight surgical patients achieved a prophylactic peak AFXa level using daily enoxaparin 30 mg. This dose is likely to provide adequate thromboprophylaxis in low-weight females.

Prophylactic unfractionated heparin and hemorrhage in neurocritically ill underweight patients: A case series and review of the literature

PURPOSE

Three cases of major bleeding associated with thromboprophylactic unfractionated heparin (UFH) therapy in underweight neurocritically ill patients are reported.

SUMMARY

Three underweight patients (body mass index of <18.5 kg/m2) were treated in the intensive care unit with major bleeds associated with UFH thromboprophylaxis. Two of the patients, a 76-year-old female and a 56-year-old female, had hemorrhages on presentation; the third patient, a 29-year-old male, developed bleeding during his admission. All 3 patients had past medical histories consisting of acute neurologic conditions within 6 weeks of presentation, including subdural hematoma, subarachnoid hemorrhage, and obstructive hydrocephalus secondary to a brain mass. All hemorrhages developed following the receipt of prophylactic UFH at doses of 5,000 units every 8 to 12 hours, which translated to high weight-based dosages (>300 units/kg/d). Additionally, hemorrhages were associated with prolonged activated partial thromboplastin time, which declined following heparin discontinuation. The major bleeds following UFH administration included an acute on chronic subdural hematoma, acute rectus sheath hematoma, and cerebellar hematoma. Stabilization of the subdural hematoma was achieved without the use of protamine and the patient was discharged in stable condition. The other 2 patients expired secondary to their hemorrhagic events. Naranjo nomogram scores for the patients indicated that heparin was the probable cause of bleed in 2 cases and a possible cause in 1 case.

CONCLUSION

Three major hemorrhages developed following the administration of UFH. Underweight patients with neurologic injury may require increased clinical vigilance, reduced doses, and pharmacodynamic monitoring to improve safety outcomes associated with thromboprophylaxis.

Enoxaparin Dosing for Venous Thromboembolism Prophylaxis in Low Body Weight Patients

Background:

The appropriate dose of enoxaparin for venous thromboembolism (VTE) prophylaxis in low body weight patients is unknown.

Objective:

The aim of this study is to evaluate the impact of enoxaparin dosing on major and minor bleeding events in low body weight patients.

Methods:

This was a retrospective cohort study of patients weighing less than 45 kg receiving subcutaneous (SC) enoxaparin for VTE prevention. The primary objective was to determine whether enoxaparin dose was associated with major and minor bleeding. The secondary objective was to determine the incidence of VTE by enoxaparin dose.

Results:

There were 173 patients included in the study, of which 37 patients received 2 different courses of enoxaparin during hospitalization, resulting in 210 enoxaparin courses. Among all enoxaparin courses, 16.2% were associated with major bleeding and 5.2% with minor bleeding. There was no difference in the incidence of major bleeding by dose (enoxaparin 30 mg SC daily, 30 mg SC twice daily, or 40 mg SC daily; P = .409). Patients who experienced major bleeding were older (54.9 ± 16.1 years) than patients who did not (48.4 ± 18.4 years) (P = .043). There was no difference in the incidence of minor bleeding by dosing schedule (P = .14). No patients experienced a VTE.

Conclusion and Relevance:

The risk of bleeding was similar by enoxaparin dose but increased with age in low body weight patients. Given the low incidence of VTE in this study, it is reasonable to consider decreasing the prophylactic enoxaparin dose in low body weight patients, especially in the elderly population.

Anticoagulation at the extremes of body weight: choices and dosing

INTRODUCTION

The landscape of therapeutic anticoagulation has changed dramatically over the past decade, with availability of direct oral anticoagulants (DOACs), which inhibit factor Xa or thrombin. However, the optimal anticoagulant agent and dosing strategy for patients at both extremes of body weight has not been established for any anticoagulant, including DOACs, vitamin K antagonists (VKA), and the various heparin options. Areas covered: This paper reviews available evidence to assist clinicians in prescribing of anticoagulation therapy at the extremes of body weight. Expert commentary: There are limited data to guide prescribing of all available anticoagulants at the extremes of weight and further research regarding efficacy and safety outcomes in these groups is required. Laboratory monitoring to guide dosing of traditional anticoagulants provides reassurance of 'predictable' efficacy. In contrast agents that are not routinely monitored by laboratory testing provide greater challenges. For example, underweight patients are at risk of receiving higher drug exposures of DOACs, whereas the use of fixed dose DOACs in obese patients may be associated with lower drug exposures.

Anticoagulants in frail patients. Seven situations at risk

In the case of venous thromboembolic disease (VTE), physicians are facing more and more difficulties in managing VTE and their treatment in frail patients. These patients could present several risk situations such as: chronic kidney disease (CKD), underweight or malnourished, falls, cognitive impairment, multi-medicated patients, cancer and pregnancy. Guidelines typically recommend anticoagulation. There are multiple challenges in the safe use of anticoagulation in frail patients, including bleeding risk, monitoring and adherence, and polypharmacy. The objective of this review is to explore these at-risk situations and to suggest adequate anticoagulation therapy, when possible, in each of these complex situations.

Gender Differences in Efficacy and Safety of Direct Oral Anticoagulants in Atrial Fibrillation: Systematic Review and Network Meta-analysis

BACKGROUND

Studies indicate that women with atrial fibrillation (AF) are less likely to receive anticoagulants despite their higher risk of stroke compared with men.

OBJECTIVE

To evaluate whether the efficacy and safety of direct oral anticoagulants (DOACs) differ in women with AF as compared with men. Our secondary aim was to examine gender differences regarding the safety and efficacy of specific DOACs.

DATA SOURCES

MEDLINE, EMBASE, Cochrane, and ClinicalTrials.gov were searched through March 2017.

STUDY SELECTION AND DATA EXTRACTION

Randomized clinical trials that reported on major bleeding and stroke with DOACs in women and men with AF were included. Meta-analysis and network meta-analysis was performed.

DATA SYNTHESIS

Five trials met the inclusion criteria. Among 66 389 patients, 37.8% were women. Women treated with DOACs were at higher risk of stroke and systemic embolism compared with men (RR = 1.19; 95% CI = 1.04-1.35; I² = 10%) but there was a significantly lower risk of major bleeding in women compared with men (RR = 0.86; 95% CI = 0.78-0.94; I² = 0%). Network meta-analyses suggested differences between various DOACs in men and women.

LIMITATIONS

Patient-level data enabling control for differences in baseline risk and head-to-head comparisons between DOACs were not available. Relevance to Patient Care and Clinical Practice: Undertreatment with DOACs among women cannot be justified.

CONCLUSION

Women treated with DOACs had a lower rate of major bleeding and higher rate of stroke and systemic emboli compared with men. Further investigation of DOACs, including differences between the DOACs in specific populations is warranted.

Enoxaparin Dosing at Extremes of Weight: Literature Review and Dosing Recommendations

OBJECTIVE

To review the literature on both thromboprophylaxis and treatment of venous thromboembolism (VTE) with enoxaparin in low- and high-body-weight patients and to make dosing and monitoring recommendations in these patient populations.

DATA SOURCES

A search using PubMed was conducted (1995 to January 2018) using the following key words: enoxaparin, body weight, AND thromboprophylaxis, or AND treatment. Additional references were identified from a review of citations.

STUDY SELECTION AND DATA EXTRACTION

Studies included examined the effect of body weight and/or body mass index (BMI) on VTE, bleeding, enoxaparin dosing, and/or anti-Xa concentrations for thromboprophylaxis and treatment-dose enoxaparin. Studies in pediatric and pregnant patients were excluded.

DATA SYNTHESIS

Optimal enoxaparin dosing strategies for VTE prophylaxis and treatment for patients at extremes of weight have not yet been elucidated by clinical trials; however, data suggest that standard dosing regimens may not be appropriate in these patients. Relevance to Patient Care and Clinical Practice: This review provides a thorough discussion on both thromboprophylaxis and treatment of VTE with enoxaparin in low- and high-body-weight patients. It includes dosing recommendations to guide clinicians caring for these patient populations.

CONCLUSIONS

Patients at extremes of weight require special consideration to determine appropriate enoxaparin doses. Specifically, low-body-weight patients may benefit from 30 mg subcutaneously daily for VTE prophylaxis, and standard weight-based dosing for VTE treatment. Conversely, in patients with BMIs ≥40 kg/m², 40 mg subcutaneously twice daily is recommended, with consideration for higher doses in patients with BMIs ≥50 kg/m².

A GENS-based approach to cardiovascular pharmacology: impact on metabolism, pharmacokinetics and pharmacodynamics

Pharmacological outcomes depend on many factors, with many of them being sexually dimorphic. Thus, physiological gender/sex (GENS) differences can influence pharmacokinetics, pharmacodynamics and, thus, bioavailability and resulting in efficacy of treatment, meaning GENS differences should be an important consideration in therapeutics. In particular, drug response can change according to different hormonal environments. Therefore, GENS-specific differences have a particular clinical relevance in terms of drug delivery, especially for those substances with a narrow therapeutic margin. Since adverse effects are more frequent among women, safety is a key issue. Overall, the status of women, from a pharmacological point of view, is often different and less studied than that of men and deserves particular attention. Further studies focused on women's responses to drugs are necessary in order to make optimal pharmacotherapeutic decisions.

Glomerular filtration rate estimated by Cockcroft-Gault formula better predicts anti-Xa levels than modification of the diet in renal disease equation in older patients with prophylactic enoxaparin

OBJECTIVES

Older people have an increased risk of low molecular weight heparin accumulation leading to an increased bleeding risk. The objective of this study was to assess whether reduced glomerular filtration rate (GFR), estimated by the Cockcroft-Gault or modification of the diet in renal disease (MDRD) equations, indicates drug accumulation by increased anti-Xa levels in older subjects receiving prophylactic enoxaparin treatment.

DESIGN

Cohort study.

SETTING

Acute geriatric units in Nancy Hospital.

PARTICIPANTS

Ninety-two consenting consecutive patients, 65 and older, confined to bed for an acute medical condition requiring enoxaparin for prevention of venous thromboembolism, and hospitalized for at least six days were enrolled.

MEASUREMENTS

Serum creatinine and peak plasma anti-Xa levels 3 to 4 hours after the daily injection of enoxaparin were measured at days 3, 6, 9 and 12 (first dose of enoxaparin at day one). Analyses of variance for repeated measures were used to evaluate significant predictors of peak anti-Xa activity in univariate and multivariate analyses.

RESULTS

A significant correlation was observed between anti-Xa activity and GFR estimated with the Cockcroft formula r=0.43. Following univariate analysis, the three factors associated with higher anti-Xa levels were a lower Cockcroft-Gault GFR (p=0.0002), female gender (p=0.0003) and a lower bodyweight (p<.0001). No significant association between anti-Xa levels and MDRD GFR (p=0.33) was observed. Following multivariate analysis, female gender (p=0.02), bodyweight (p=0.04) and Cockcroft GFR (p=0.05) remained independent determinants of anti-Xa levels.

CONCLUSION

In hospitalized patients older than 65 years old, the Cockcroft-Gault equation, in contrast to the MDRD equation, is able to predict the risk of higher anti-Xa levels.

A dose-ranging study evaluating the oral factor Xa inhibitor edoxaban for the prevention of venous thromboembolism in patients undergoing total knee arthroplasty

BACKGROUND

Edoxaban (the free base of DU-176b) is an oral, direct factor (F)Xa inhibitor in clinical development for the prevention and treatment of thromboembolic events.

OBJECTIVES

The aim of the present study was to evaluate the efficacy and safety of edoxaban for the prevention of venous thromboembolism (VTE) in patients undergoing total knee arthroplasty (TKA).

PATIENTS/METHODS

This was a randomized, double-blind, placebo-controlled, multicenter study conducted in Japan. A total of 523 Japanese patients were assigned to receive edoxaban 5, 15, 30 or 60 mg once daily or placebo for 11-14 days. A placebo control was used as neither low-molecular-weight heparin (LMWH) nor fondaparinux had been approved for thromboprophylaxis at the time of the study in Japan. The primary efficacy outcome was the incidence of VTE (lower-extremity deep vein thrombosis, symptomatic pulmonary embolism or symptomatic deep vein thrombosis). The primary safety outcome was the incidence of major and clinically relevant non-major bleeding.

RESULTS

Edoxaban produced a significant dose-related reduction in VTE: the incidence of VTE was 29.5%, 26.1%, 12.5% and 9.1% in the edoxaban 5-, 15-, 30- and 60-mg treatment groups vs. 48.3% in the placebo group. The incidence of major and clinically relevant non-major bleeding was similar across all groups without any significant differences among edoxaban doses or between edoxaban and placebo.

CONCLUSIONS

Edoxaban demonstrated significant dose-dependent reductions in VTE in patients undergoing TKA with a bleeding incidence similar to placebo. [This trial is registered with JAPIC, JapicCTI-060283 (ja).].