Understanding the pharmacogenetic approach to warfarin dosing

Machine learning models to predict the warfarin discharge dosage using clinical information of inpatients from South Korea

As warfarin has a narrow therapeutic window and obvious response variability among individuals, it is difficult to rapidly determine personalized warfarin dosage. Adverse drug events(ADE) resulting from warfarin overdose can be critical, so that typically physicians adjust the warfarin dosage through the INR monitoring twice a week when starting warfarin. Our study aimed to develop machine learning (ML) models that predicts the discharge dosage of warfarin as the initial warfarin dosage using clinical data derived from electronic medical records within 2 days of hospitalization. During this retrospective study, adult patients who were prescribed warfarin at Asan Medical Center (AMC) between January 1, 2018, and October 31, 2020, were recruited as a model development cohort (n = 3168). Additionally, we created an external validation dataset (n = 891) from a Medical Information Mart for Intensive Care III (MIMIC-III). Variables for a model prediction were selected based on the clinical rationale that turned out to be associated with warfarin dosage, such as bleeding. The discharge dosage of warfarin was used the study outcome, because we assumed that patients achieved target INR at discharge. In this study, four ML models that predicted the warfarin discharge dosage were developed. We evaluated the model performance using the mean absolute error (MAE) and prediction accuracy. Finally, we compared the accuracy of the predictions of our models and the predictions of physicians for 40 data point to verify a clinical relevance of the models. The MAEs obtained using the internal validation set were as follows: XGBoost, 0.9; artificial neural network, 0.9; random forest, 1.0; linear regression, 1.0; and physicians, 1.3. As a result, our models had better prediction accuracy than the physicians, who have difficulty determining the warfarin discharge dosage using clinical information obtained within 2 days of hospitalization. We not only conducted the internal validation but also external validation. In conclusion, our ML model could help physicians predict the warfarin discharge dosage as the initial warfarin dosage from Korean population. However, conducting a successfully external validation in a further work is required for the application of the models.

Dentistry and Drug Adverse Events: Between Responsibilities and Regulations

The purpose of this paper is to renew interest and attention to the medical history, prescription, and/or use of drugs during dental practice. The work analyzes the issue of the use of drugs in dentistry from both a clinical and a medical-legal point of view. The laws governing the matter were also taken into consideration, relating them to the roles of prescriber and user that the dentist can acquire. Analysis of various aspects of this matter demonstrates that it is necessary for dentists to know the drugs and medical substances, their characteristics and properties, related effects, and interactions in order to use them appropriately and adequately. Knowledge of interferences, reactions, and adverse events or complications helps to reduce errors and protect patients' health. Furthermore, knowledge of the national and international reference standards relating to the use of drugs leads to a reduction in medico-legal questions. In conclusion, knowledge and adequate and appropriate use of drugs reduces the possibility of accidents, adverse events, medico-legal consequences, and disputes with patients. Documented and traceable choices allow the analysis and valuation of professional conduct. Authors perceived the topic of informed consent of patients as relevant to the adequate procedure of prescribing drugs related to dentistry practice; therefore, representative conditions of patients at risk should be illustrated in practice. Legal duties related to physician drug prescription and use must be considered and carefully checked.

[Translational Research Based on Understanding the Regulatory Mechanisms of in Vivo Behaviors of Fat-soluble Compounds]

Several fat-soluble compounds such as cholesterol and fat-soluble vitamins have important physiological activities in the body, and their excess and/or deficiency have been reported to be closely associated with the onset and progression of several conditions such as lifestyle-related diseases. It is important to clarify not only the physiological activities but also in vivo kinetics of fat-soluble compounds to understand their in vivo activity (toxicity). This review introduces our recent (reverse) translational research in a combination of basic and clinical studies to reveal the regulatory mechanisms of in vivo behaviors of fat-soluble compounds and effects of their disruption in humans.

Antithrombotic Effect of Artemisia princeps Pampanini Extracts in Vitro and in FeCl3 -Induced Thrombosis Rats

Extracts of several plants possess antithrombotic effects. Herein, we examined the antithrombotic effects of different extracts of Artemisia princeps Pampanini prepared using distilled water, hot distilled water, 70% ethanol, or subcritical water. The antithrombotic effects were determined using a co-culture system consisting of tumor necrosis factor-alpha (TNF-α)-treated EA.hy926 cells and THP-1 cells. In addition, the coagulation time of plasma collected from healthy volunteers was evaluated in terms of the prothrombin time and activated partial thromboplastin time. A carotid arterial thrombosis model was induced by ferric chloride in Sprague Dawley rats. The rats were treated with either sterile water or three different doses of the subcritical water extract for 2 weeks. The thrombus weight, gene expression of cell adhesion molecules, and histological characteristics were assessed. The results of in vitro studies revealed a significant inhibition in the adhesion of monocytes to EA.hy926 cells stimulated by TNF-α in the subcritical water extract-treated group. We also observed considerable suppression of the occlusion and mRNA expression of cell adhesion molecules in the in vivo experiments. This study suggests that Artemisia princeps Pampanini may have the potential to improve blood coagulation.

Genetic variant in the promoter region of microRNA‑137 reduces the warfarin maintenance dose in patients with atrial fibrillation

A substantial body of research has confirmed that Vitamin K epoxide reductase complex subunit 1 (VKORC1) plays a role in contributing to the high interpatient variability in the warfarin maintenance dose. The aim of the present study was to examine the impact of SNPs of miR‑137 on the warfarin maintenance dose. Computational analysis and luciferase assay were used to search the targets of miR‑137, and luciferase assay was also used to confirm the effect of the polymorphisms on the transcription of the promoter. The regulatory relationship between miR‑137 and VKORC1 was detected using real‑time PCR. We then performed statistical analysis to find the warfarin maintenance dose in the different groups. A total of 155 subjects were enrolled in our research, and the characteristics of the patients were collected. Using computational analysis, we identified that miR‑137 binds to the VKORC1 3'untranslated region (3'UTR) and regulates the expression of VKORC1. This hypothesis was confirmed by luciferase reporter assay as miR‑137 significantly reduced the VKORC1 3'UTR luciferase activity, while the luciferase activity of mutant VKORC1 3'UTR was similar to the scramble control. According to the result of the luciferase reporter assay, we found that miR‑137 SNP with the presence of the A allele apparently reduced the luciferase activity. Using real‑time PCR, we revealed that miR‑137 negatively regulated the expression of VKORC1 in a concentration‑dependent manner in liver cells. Furthermore, no difference was noted regarding the warfarin maintenance dose between the different age or gender groups, and furthermore AC + AA carriers showed a markedly higher warfarin maintenance dose than CC carriers. These findings collectively provide support that VKORC1 is a direct target of miR‑137 and the miR‑137 rs2660304 polymorphism is associated with warfarin maintenance dose in patients with atrial fibrillation. The rs2660304 polymorphism is a potential biomarker for predicting the clinical efficacy of warfarin in these patients.

Influence of UDP-Glucuronosyltransferase Polymorphisms on Stable Warfarin Doses in Patients with Mechanical Cardiac Valves

AIM

This study aimed to evaluate the effect of uridine diphosphate (UDP)-glucuronosyltransferase (UGT) polymorphisms on warfarin dosing requirements in patients with mechanical cardiac valves.

METHODS

A total of 191 patients with stable warfarin doses from the EAST Group of Warfarin were included in this study. The influence of genetic polymorphisms on stable warfarin doses was investigated by genotyping 6 single nucleotide polymorphisms (SNPs): vitamin K epoxide reductase complex 1 (VKORC1) rs9934438, cytochrome P450 (CYP) 2C9 rs1057910, CYP4F2 rs2108622, and UGT1A1 (rs887829, rs4148323, and rs4124874). An additional subgroup analysis was carried out using patients with wild-type homozygote carriers of CYP2C9.

RESULTS

One UGT1A1 SNP of rs887829 (C>T) exhibited significant association with stable warfarin doses in the study population and subgroup. Patients with the T allele in UGT1A1 rs887829 (CT or TT) required higher doses than those with the CC genotype in the study population (6.3 ± 2.4 mg vs. 5.2 ± 1.6 mg, P = 0.003). Similarly, in the subpopulation of AA carriers in the CYP2C9 gene, patients with the T allele required significantly higher doses of warfarin than those with other genotypes of rs887829 (6.5 ± 2.4 vs. 5.3 ± 1.5 mg, P = 0.002). Approximately 45.1% of overall interindividual variability in warfarin dose requirement was explained by the multivariate regression model. VKORC1, CYP2C9, UGT1A1 rs887829, age, and CYP4F2 accounted for 28.2%, 6.6%, 5.5%, 3.0%, and 1.8% of the variability, respectively.

CONCLUSION

Our results suggest that UGT1A1 could be a determinant of stable warfarin doses.

Reinitiating warfarin: relationships between dose and selected patient, clinical and hospital measures

BACKGROUND

Warfarin is an oral anticoagulant used in the long-term treatment/prevention of venothromboembolic disease. Patients undergoing elective surgical and non-surgical procedures may require temporary warfarin discontinuation followed by reinitiation after their procedure. Because little information is available regarding best methods for warfarin reinitiation, we investigated current practices to inform management decisions.

METHODS

Subjects were required to have a known and stable warfarin dose prior to discontinuation, which was operationalized by requiring, within 7-days prior to discontinuation, that they have at least one INR in therapeutic range (2.0-3.5), no INR(s) out of range, and no more than a 15% change in warfarin dose. Stable dose prior to discontinuation was defined as the average daily dose received in the 7 days immediately prior to discontinuation. Reinitiation dose was defined as the average daily dose received in the first 3 days after warfarin was restarted. Subjects were divided into three groups based on whether they received approximately the same, a higher, or a lower dose at reinitiation and were also grouped by calendar time into three distinct periods that reflected differing levels of availability of electronic and patient care data that may impact reinitiation dose decisions. These groupings facilitated analyses and descriptions of trends in reinitiation dosing and supported other analyses, including tests for association between dose group and selected subject demographic, clinical, medication and hospitalization measures. All study data were abstracted from Marshfield Clinic electronic patient care and administrative databases and electronic patient care databases from Ministry St. Joseph's Hospital (Marshfield, WI).

RESULTS

We identified 205 subjects with warfarin temporarily discontinued between 1994 and 2012: 99 subjects in same dose group, 32 subjects in the low group, and 74 subjects in the high group. Because relatively wide differences were observed in the proportion of same dose subjects during more recent years (2007-2012) compared to earlier years (54% vs 35%), we focused our analyses on this recent period, which included 140 subjects. Review of physician notes and other documents yielded virtually no information about reasons for reinitiation dose decisions. In addition, tests for association between reinitiation dose group and subject demographic, clinical, medication and hospital measures were uniformly uninformative.

CONCLUSIONS

We observed varied dosing strategies for reinitiating patients on warfarin and, in more recent years, an apparent trend toward reinitiating patients on the same dose. However we could not associate dosing strategy with specific patient demographic, clinical, medication or hospital factors. Many factors influence whether a physician reinitiates a patient at a different dose than his/her prior stable warfarin dose. However, in the absence of clinical indications for modification, we believe patients with a previously established effective dose should be reinitiated at that same dose following temporary warfarin discontinuation.

Genotype-Guided Dosing of Coumarin Anticoagulants

Background:

Coumarin anticoagulants (acenocoumarol, phenprocoumon, and warfarin) are generally used for the prevention of stroke in patients with atrial fibrillation or for the therapy and prevention of venous thromboembolism. However, the safe use of coumarin anticoagulants is restricted by a narrow therapeutic window and large interindividual dosing variations. Some studies found that the effectiveness and safety of coumarin anticoagulants therapy were increased by pharmacogenetic-guided dosing algorithms, while others found no significant effect of genotype-guided therapy.

Methods:

Four electronic databases were searched from January 1, 2000, to March 1, 2014, for randomized controlled trials of patients who received coumarin anticoagulants according to genotype-guided dosing algorithms. The primary outcome was the percentage of time that the international normalized ratio (INR) was within the normal range (2.0-3.0). Secondary outcomes included major bleeding events, thromboembolic events, and INR ≥4 events.

Results:

Eight studies satisfied the inclusion and exclusion criteria. Genotype-guided dosing of coumarin anticoagulants improved the percentage of time within the therapeutic INR range (95% confidence interval [CI], 0.02-0.28; P = .02; I2 = 70%). Subgroup analysis was performed after dividing the nongenotype-guided group into a standard-dose group (95% CI, 0.14-0.49; P = .0004; I2 = 50%) and a clinical variables-guided dosing algorithm group (95% CI, −0.07-0.15; P = .48; I2 = 34%). There is a statistically significant reduction in numbers of secondary outcomes (INR ≥4 events, major bleeding events, and thromboembolic events; 95% CI, 0.79-1.00; P = .04). Subgroup analysis of secondary outcomes showed no significant difference between genotype-guided dosing and clinical variables-guided dosing (95% CI, 0.84-1.10; P = .57; I2 = 11%), but genotype-guided dosing reduced secondary outcomes compared with standard dosing (95% CI, 0.62-0.92; P = .006; I2 = 0%).

Conclusions:

This meta-analysis showed that genotype-guided dosing increased the effectiveness and safety of coumarin therapy compared with standard dosing but did not have advantages compared with clinical variables-guided dosing.

Warfarin, a potential pollutant in aquatic environment acting through Pxr signaling pathway and γ-glutamyl carboxylation of vitamin K-dependent proteins

Warfarin-induced vitamin K (VK) recycling impairment is used worldwide as a rodenticide and human thromboembolic prophylactic. Since VK metabolism/signaling pathways have been conserved throughout vertebrate evolution, its release to the environment might impact on aquatic organisms. Present study assessed the toxic effect of warfarin (0, 5, 25 and 125 mg L(-1)) on zebrafish development and characterized underlying mechanisms of action through qPCR analysis of VK-related genes. Expression of pregnane X receptor (pxr), the nuclear receptor binding vitamin K, was ubiquitous in zebrafish and suggests that warfarin exposure may interfere with several biological processes. Indeed, warfarin exposure of zebrafish larvae caused hemorrhages in brain, skeletal deformities and triggered ectopic calcifications, which may be the consequence of an altered γ-carboxylation of VK-dependent proteins and/or pxr signaling. This study provides new insights into warfarin effects as a bone homeostasis disruptor and soft tissue calcification inductor, and its potential risk for aquatic environments.

Screening for 392 polymorphisms in 141 pharmacogenes

Pharmacogenomics is the study of the association between inter-individual genetic differences and drug responses. Researches in pharmacogenomics have been performed in compliance with the use of several genotyping technologies. In this study, a total of 392 single-nucleotide polymorphisms (SNPs) located in 141 pharmacogenes, including 21 phase I, 13 phase II, 18 transporter and 5 modifier genes, were selected and genotyped in 150 subjects using the GoldenGate assay or the SNaPshot technique. These variants were in Hardy-Weinberg equilibrium (HWE) (P>0.05), except for 22 SNPs. Genotyping of the 392 SNPs revealed that the minor allele frequencies of 47 SNPs were <0.05, 105 SNPs were monomorphic and 22 variants were not in HWE. Also, based on previous studies, we predicted the association between the polymorphisms of certain pharmacogenes, such as cytochrome P450 2D6, cytochrome P450 2C9, vitamin K epoxide reductase complex, subunit 1, cytochrome P450 2C19, human leukocyte antigen, class I, B and thiopurine S-methyltransferase, and drug efficacy. In conclusion, our study demonstrated the allele distribution of SNPs in 141 pharmacogenes as determined by high-throughput screening. Our results may be helpful in developing personalized medicines by using pharmacogene polymorphisms.

Does CALU SNP rs1043550 contribute variability to therapeutic warfarin dosing requirements?

OBJECTIVES

Calumenin, a molecular chaperone, exerts a regulatory effect on the vitamin K-dependent γ-carboxylation redox cycle that inhibits transfer of the reduced vitamin K from VKORC1, the pharmacological target of warfarin, to the γ-carboxylase. Because of its polymorphic structure and central role in the warfarin metabolic pathway, a contributory role for calumenin to warfarin dose variability has been posited. The current study sought to validate modulation of therapeutic dosing requirements by a single nucleotide polymorphisms (SNP) occurring in the calumenin gene (CALU) reported in previous studies. The CALU SNP was further modeled to detect interaction with SNPs occurring in VKORC1, CYP2C9, and CYP4F2 genes and characterize any additional contribution to variability in therapeutic warfarin dose requirement.

SETTING

The study was undertaken in an established, well-characterized cohort of subjects treated with warfarin in the Anticoagulation Clinic of Marshfield Clinic in Marshfield, Wisconsin.

METHODS

Subjects (N=491) previously genotyped for SNPS known to contribute variability to therapeutic warfarin dose requirement were genotyped for CALU SNP rs1043550, using TaqMan assays. Contribution of CALU SNP rs1043550 was modeled relative to other genotypic and phenotypic characteristics including gender, diagnosis, age, body surface area, underlying indication for warfarin, comorbidities, and pharmacological exposures. Interaction between SNPs impacting on warfarin dose requirements and calumenin SNPs was also modeled.

RESULTS

Small differences in warfarin dosing requirements detected among individuals encoding the mutant G allele in the calumenin SNP were not statistically or clinically significant relative to therapeutic warfarin dose requirement and did not independently contribute significantly to the warfarin dosing model. Interaction between calumenin and VKORC1 SNPs contributed only minor additional variability to that ascribed to the wild type VKORC1 genotype.

CONCLUSIONS

The impact of the CALU SNP on warfarin dose variability was minor and did not contribute significantly to therapeutic warfarin dose requirement in our study cohort. While no contribution was noted for the SNP examined in the present study, further examination of interaction between genetic elements contributing major impact on therapeutic warfarin dose requirements and genes exhibiting a lesser contribution is warranted.

Correlation between single nucleotide polymorphisms in CYP4F2 and warfarin dosing in Chinese valve replacement patients

BACKGROUND

Individuals with implanted mechanical valve prostheses require lifelong anticoagulation therapy with warfarin. The narrow therapeutic index of warfarin makes it difficult to dose and maintain proper anticoagulation. A number of single nucleotide polymorphisms (SNPs) affecting vitamin K or warfarin metabolism have been shown to affect warfarin dosing. Our aim was to study the effect of the CYP4F2 rs2108622-1347 (C > T) variant on warfarin dosing in Chinese patients.

METHODS

We studied 352 patients after heart valve replacement surgery. Warfarin dosing for patients was adjusted to achieve 1.8 ≤ INR ≤ 2.5. We determined the presence of SNPs in CYP4F2 in these patients and investigated their association with warfarin dosing.

RESULTS

We found the frequency of the CYP4F2 rs2108622 C allele was 79.5% and T-allele frequency was 20.5%. The warfarin dose requirement for CC individuals was significantly lower than that for CT or TT individuals (P < 0.05). TT-homozygous individuals required a 0.56 mg/day higher dose of warfarin than their CC counterparts.

CONCLUSIONS

This study demonstrates that CYP4F2 rs2108622 significantly affects the warfarin dose requirement to achieve adequate anticoagulant activity in Chinese individuals. Genotyping of this SNP may allow clinicians to determine the initiation dose for patients following valve-replacement surgery in China.

Prediction of warfarin dose: why, when and how?

Prediction models are the key to individualized drug therapy. Warfarin is a typical example of where pharmacogenetics could help the individual patient by modeling the dose, based on clinical factors and genetic variation in CYP2C9 and VKORC1. Clinical studies aiming to show whether pharmacogenetic warfarin dose predictions are superior to conventional initiation of warfarin are now underway. This review provides a broad view over the field of warfarin pharmacogenetics from basic knowledge about the drug, how it is monitored, factors affecting dose requirement, prediction models in general and different types of prediction models for warfarin dosing.

Absence of novel CYP4F2 and VKORC1 coding region DNA variants in patients requiring high warfarin doses

OBJECTIVE

Warfarin is an FDA-approved oral anticoagulant for long-term prevention of thromboembolism. Substantial inter-individual variation in dosing requirements and the narrow therapeutic index of this widely-prescribed drug make safe initiation and dose stabilization challenging. Single nucleotide polymorphisms (SNPs) occurring in CYP2C9, VKORC1, and CYP4F2 genes are known to impact dose, and VKORC1 and CYP4F2 polymorphisms are associated with higher therapeutic dose requirements in our cohort. However, the most advanced regression models using personal, clinical, and genetic factors to predict individual stable dose account for only 50% to 60% of the observed variability in stable therapeutic dose in Caucasians.

DESIGN AND METHODS

In this study, we used DNA sequence analysis to determine whether additional variants in CYP4F2 and VKORC1 gene coding regions contribute to variable dosing requirements among individuals for whom the actual dose was the highest relative to regression model- predicted dose.

RESULTS AND CONCLUSIONS

No novel DNA variants in the coding regions of these genes were identified among subjects requiring high warfarin doses, suggesting that other factors yet to be defined contribute to variability in warfarin dose requirements in this subset of our cohort.

Personalized vascular medicine: individualizing drug therapy

Personalized medicine refers to the application of an individual's biological fingerprint - the comprehensive dataset of unique biological information - to optimize medical care. While the principle itself is straightforward, its implementation remains challenging. Advances in pharmacogenomics as well as functional assays of vascular biology now permit improved characterization of an individual's response to medical therapy for vascular disease. This review describes novel strategies designed to permit tailoring of four major pharmacotherapeutic drug classes within vascular medicine: antiplatelet therapy, antihypertensive therapy, lipid-lowering therapy, and antithrombotic therapy. Translation to routine clinical practice awaits the results of ongoing randomized clinical trials comparing personalized approaches with standard of care management.