An Investigation of CYP2D6 Genotype and Response to Metoprolol CR/XL During Dose Titration in Patients With Heart Failure: A MERIT-HF Substudy

Clinical Pharmacogenetics Implementation Consortium Guideline (CPIC) for CYP2D6, ADRB1, ADRB2, ADRA2C, GRK4, and GRK5 Genotypes and Beta-Blocker Therapy

Beta-blockers are widely used medications for a variety of indications, including heart failure, myocardial infarction, cardiac arrhythmias, and hypertension. Genetic variability in pharmacokinetic (e.g., CYP2D6) and pharmacodynamic (e.g., ADRB1, ADRB2, ADRA2C, GRK4, GRK5) genes have been studied in relation to beta-blocker exposure and response. We searched and summarized the strength of the evidence linking beta-blocker exposure and response with the six genes listed above. The level of evidence was high for associations between CYP2D6 genetic variation and both metoprolol exposure and heart rate response. Evidence indicates that CYP2D6 poor metabolizers experience clinically significant greater exposure and lower heart rate in response to metoprolol compared with those who are not poor metabolizers. Therefore, we provide therapeutic recommendations regarding genetically predicted CYP2D6 metabolizer status and metoprolol therapy. However, there was insufficient evidence to make therapeutic recommendations for CYP2D6 and other beta-blockers or for any beta-blocker and the other five genes evaluated (updates at www.cpicpgx.org).

Impact of CYP2D6 and ADRB1 polymorphisms on heart rate of post-PCI patients treated with metoprolol

Aim: To explore the effect of CYP2D6*10 (100C > T) and ADRB1 1165 G > C polymorphisms on heart rate of post-PCI (percutaneous coronary intervention) patients treated with metoprolol succinate sustained-release tablets. Methods: A total of 756 inpatients with metoprolol succinate sustained-release tablets were selected and the genotypes of CYP2D6*10 and ADRB1 1165G > C were detected in 319 patients using gene chip detection. The target heart rate was defined as a resting heart rate < 70 beats/min. Clinical data were collected. Results: A total of 319 inpatients were enrolled in the study. The mutant allele frequencies of CYP2D6 and ADRB1 were 57.21 and 69.44%, respectively. Whatever the dose of metoprolol, the heart rates were lower in patients with homozygous mutation of CYP2D6 than those with heterozygous mutation and wild-type (p < 0.05). Nevertheless, this effect was not seen between different genotypes of ADRB1. Logistic regression analysis showed that the dose of metoprolol and the genotypes of CYP2D6 were predictors of heart rate <70 beats/min in these patients. Further multivariate analysis indicated that patients with homozygous mutation had better control of heart rates compared with those with wild-type and heterozygous mutation of CYP2D6*10 genotypes (all: p < 0.001). Conclusion:CYP2D6*10 polymorphisms were associated with the heart rate of post-PCI patients treated with metoprolol succinate sustained-release tablets.

Genetic polymorphisms in ADRB1, ADRB2 and CYP2D6 genes and response to beta-blockers in patients with acute coronary syndrome

Betablockers (BBs) are prescribed for ischaemia in patients with acute coronary syndrome (ACS). In Spain, bisoprolol and carvedilol are the most prescribed BBs, but patients often had to discontinue them due to adverse effects. Single nucleotide polymorphisms (SNPs) in ADRB1, ADRB2 and CYP2D6 genes have strong evidence of pharmacogenetic association with BBs in heart failure or hypertension, but the evidence in ACS is limited. Therefore, our study focuses on investigating how these genes influence the response to BBs in ACS patients. We analysed the association between SNPs in ADRB1 Gly389Arg (rs1801253) and Ser49Gly (rs1801252), ADRB2 Gly16Arg (rs1042713) and Glu27Gln (rs1042714), and CYP2D* 6 (*2- rs1080985, *4- rs3892097, *10 - rs1065852) and the occurrence of bradycardia/hypotension events during one year of follow-up. We performed an observational study and included 285 ACS-PCI-stent patients. A first analysis including patients treated with bisoprolol and a second analysis including patients treated with other BBs were performed. We found that the presence of the G allele (Glu) of the ADRB2 gene (rs1042714; Glu27Gln) conferred a protective effect against hypotension-induced by BBs; OR (CI 95%) = 0,14 (0,03-0,60), p < 0.01. The ADRB2 (rs1042713; Gly16Arg) GG genotype could also prevent hypotensive events; OR (CI 95%) = 0.49 (0.28-0.88), p = 0015. SNPs in ADRB1 and CYP2D6 * 2, CYP2D6 * 4 weren´t associated with primary events. The effect of CYP2D6 * 10 does not seem to be relevant for the response to BBs. According to our findings, SNPs in ADRB2 (rs1042713, rs1042714) could potentially affect the response and tolerance to BBs in ACS-patients. Further studies are necessary to clarify the impact of ADRB2 polymorphisms.

Cardiovascular precision medicine - A pharmacogenomic perspective

Precision medicine envisages the integration of an individual's clinical and biological features obtained from laboratory tests, imaging, high-throughput omics and health records, to drive a personalised approach to diagnosis and treatment with a higher chance of success. As only up to half of patients respond to medication prescribed following the current one-size-fits-all treatment strategy, the need for a more personalised approach is evident. One of the routes to transforming healthcare through precision medicine is pharmacogenomics (PGx). Around 95% of the population is estimated to carry one or more actionable pharmacogenetic variants and over 75% of adults over 50 years old are on a prescription with a known PGx association. Whilst there are compelling examples of pharmacogenomic implementation in clinical practice, the case for cardiovascular PGx is still evolving. In this review, we shall summarise the current status of PGx in cardiovascular diseases and look at the key enablers and barriers to PGx implementation in clinical practice.

Females present higher dose-adjusted drug concentrations of metoprolol and allopurinol/oxypurinol than males

Females present a higher risk of adverse drug reactions. Sex-related differences in drug concentrations may contribute to these observations but they remain understudied given the underrepresentation of females in clinical trials. The aim of this study was to investigate whether anthropometric and socioeconomic factors and comorbidities could explain sex-related differences in concentrations and dosing for metoprolol and oxypurinol, the active metabolite of allopurinol. We conducted an analysis of two cross-sectional studies. Participants were self-described "White" adults taking metoprolol or allopurinol selected from the Montreal Heart Institute Hospital Cohort. A total of 1007 participants were included in the metoprolol subpopulation and 459 participants in the allopurinol subpopulation; 73% and 86% of the participants from the metoprolol and allopurinol subpopulations were males, respectively. Females presented higher age- and dose-adjusted concentrations of both metoprolol and oxypurinol (both p < 0.03). Accordingly, females presented higher unadjusted and age-adjusted concentration:dose ratio of both metoprolol and allopurinol/oxypurinol compared to males (all p < 3.0 × 10^-4 ). Sex remained an independent predictor of metoprolol concentrations (p < 0.01), but not of oxypurinol concentrations, after adjusting for other predictors. In addition to sex, age, daily dose, use of moderate to strong CYP2D6 inhibitors, weight, and CYP2D6 genotype-inferred phenotype were associated with concentrations of metoprolol (all p < 0.01). Daily dose, weight, estimated glomerular filtration rate (eGFR), and employment status were associated with oxypurinol concentrations (all p < 0.01). Females present higher dose-adjusted concentrations of metoprolol and oxypurinol than males. This suggests the need for sex-specific dosing requirements for these drugs, although this hypothesis should be validated in prospective studies.

Metoprolol and CYP2D6: A Retrospective Cohort Study Evaluating Genotype-Based Outcomes

Metoprolol is a medication commonly utilized in select patients to achieve a reduction in heart rate, systolic blood pressure, or other indications. A majority of metoprolol metabolism occurs via CYP2D6. Decreased expression of the CYP2D6 enzyme increases the concentration of metoprolol. Current pharmacogenomics guidelines by the Dutch Pharmacogenomics Working Group recommend slower titrations and dose decreases to minimize adverse effects from poor metabolizers or normal metabolizers taking concomitant medications that are strong inhibitors of CYP2D6 (phenoconverters). This study aimed to evaluate adverse effects such as bradycardia, hypotension, and syncope in patients who are expected to have absent CYP2D6 enzyme activity due to drug–drug or drug–gene interactions. The secondary aims of this study were to evaluate heart rate measurements for the included participants. Retrospective data were collected for individuals with CYP2D6 genotyping results obtained for clinical purposes. Three categories (CYP2D6 normal metabolizers, poor metabolizers, and phenoconverters) were assigned. A total of 325 participants were included. There was no statistically significant difference found in the primary composite outcome between the three metabolizer groups (p = 0.054). However, a statistically significant difference was identified in the incidences of bradycardia between the poor metabolizers and the normal metabolizers or phenoconverters (p < 0.0001). The average heart rates were 2.8 beats per minute (bpm) and 2.6 bpm lower for the poor metabolizer and phenoconverter groups, respectively, compared to the normal metabolizers (p < 0.0001 for both comparisons). This study further supports the role of genetic testing in precision medicine to help individualize patient care as CYP2D6 poor metabolizers taking metoprolol were found to have an increase in bradycardia. Additional research is needed to clarify the dose relationship in this drug–gene interaction.

Determination of CYP450 activities in diabetes mellitus rats by a UHPLC-MS/MS method

In this study, we investigated the effect of type 1 diabetes mellitus on the modulation of the activities of CYP450s in dynamics by a UHPLC-MS/MS method. The diabetic rat model was constructed by an intraperitoneal single injection of streptozotocin. Fasting blood glucose levels > 16.7 mmol/L were considered as diabetic. The rats were given a cocktail of four probe drugs (10 mg/kg phenacetin, 1 mg/kg tolbutamide, 10 mg/kg metoprolol, and 10 mg/kg midazolam) by oral administration for the pharmacokinetic study. Thereafter, the metabolic ratio (MR) of the metabolites to probe substrates were determined. The results indicated that two weeks after diabetes was induced, diabetes increased the MRs of acetaminophen/phenacetin (CYP1A2) and 4-hydroxyl tolbutamide/tolbutamide (CYP2C9); however, it decreased the MRs of α-hydroxy metoprolol/metoprolol (CYP2D6) and 1-hydroxy midazolam/midazolam (CYP3A4). Two months after diabetes was induced, diabetes increased the MRs of acetaminophen/phenacetin and 4-hydroxyl tolbutamide/tolbutamide. The MR of α-hydroxy metoprolol/metoprolol was decreased and the MR of 1-hydroxy midazolam/midazolam was increased but the difference was not significant. According to the results, CYP1A2 and CYP2C9 activities were enhanced in the diabetic rats. and CYP2D6 activity was inhibited in a short period of diabetes; however, the decrease in CYP2D6 activity was not significant in the long period. CYP3A4 activity was decreased in a short period of diabetes and increased in a long period of diabetes but was not significant in the two periods. This study suggests the activity change rule of the CYP450 enzyme system in diabetes mellitus, which can provide a reference for precise clinical medication.

Acute liver injury induced by drug interaction between dacomitinib and metoprolol due to the inhibition of CYP2D6 by dacomitinib

Introduction

In recent years, oral antineoplastic agents are commonly used in antitumor therapy. The interaction between drugs may affect the efficacy of drugs or lead to adverse reactions. We describe the case of a patient who presented acute liver injury, possibly induced by the concomitant use of metoprolol and dacomitinib.

Case report

A 62-year-old male patient with non-small cell lung cancer was admitted for anti-cancer treatment. He regularly took metoprolol tartrate 12.5 mg, 2/day for hypertension. He was treated with dacomitinib according to EGFR Exon21 L858R positive. After 3 days of dacomitinib, the patient's alanine aminotransferase (ALT) and glutathione aminotransferase (AST) increased, and the heart rate and systolic blood pressure of the patient decreased significantly. The patient was diagnosed with acute liver injury.

Management and outcomes

Dacomitinib was discontinued and glutathione, magnesium isoglycyrrhizinate were given to treat acute liver injury. Two days after discontinued dacomitinib, the patient's heart rate increased, but the ALT and AST of the patient elevated again. Metoprolol tartrate was subsequently discontinued and the ALT and AST gradually decreased and the patient discharged from the hospital eight days later with his liver function improved.

Discussion

To our knowledge, this is the first case in the literature of acute liver injury possibly induced by the interaction between metoprolol and dacomitinib. The interaction most likely arose because dacomitinib is a CYP2D6 strong inhibitor and could therefore impair the metabolism of metoprolol (a CYP2D6 substrate) and increase its serum concentration. Therefore, hepatic function should be carefully monitored in patients treated with dacomitinib and metoprolol and other inhibitors or inducers of CYP2D6.

Opioid-Related Genetic Polymorphisms of Cytochrome P450 Enzymes after Total Joint Arthroplasty: A Focus on Drug-Drug-Gene Interaction with Commonly Coprescribed Medications

Pharmacogenomic testing, together with the early detection of drug-drug-gene interactions (DDGI) before initiating opioids, can improve the selection of dosage and reduce the risk of adverse drug interactions and therapeutic failures following Total Joint Arthroplasty. The variants of CYP genes can mediate DDGI. Orthopedic surgeons should become familiar with the genetic aspect of opioid use and abuse, as well as the influence of the patient genetic makeup in opioid selection and response, and polymorphic variants in pain modulation.

Impact of the CYP2D6 Genotype on Metoprolol Tolerance and Adverse Events in Elderly Chinese Patients With Cardiovascular Diseases

The latest consensus has changed CYP2D6 genotyping among Chinese population, while its impact on metoprolol tolerance and adverse events in elderly Chinese patients with cardiovascular diseases remains unclear. In this study, we prospectively included elderly patients who started metoprolol treatment for cardiovascular indications. According to the latest consensus on CYP2D6 genotype-to-phenotype translation, the patients were categorized as normal, intermediate, or poor metabolizers (NMs, IMs, or PMs, respectively) by detecting the presence of the CYP2D6*1, *2, *5, *10, and *14. Logistic regression model was used to analyze the correlation between the CYP2D6 phenotype and incidence of adverse events, which were assessed over a 12-week period. In this study, there were 651 (62.7%) NMs, 385 (37.1%) IMs, and 3 (0.3%) PMs. After 12 weeks of follow-up, compared with NMs, IMs had the lower maintenance dose [50.0 (25.0–50.0) mg/day vs. 25.0 (25.0–50.0) mg/day, p < 0.001] and lower weight-adjusted maintenance doses (0.52 ± 0.25 mg/day/kg vs. 0.42 ± 0.22 mg/day/kg, p < 0.001), and had higher incidence of postural hypotension (6.0% vs. 10.9%, p = 0.006), bradycardia (21.5% vs. 28.6%, p = 0.011), asystole (0.8% vs. 3.1%, p = 0.009) and syncope (2.0% vs. 6.2%, p = 0.001). In logistic regression model, the overall incidence of adverse events was 1.37-fold larger in IMs than in NMs (odds ratio = 1.37, 95% confidence interval = 1.05–1.79, p = 0.021). We conclude that IMs have lower tolerance and higher incidence of metoprolol-related adverse events than NMs in elderly Chinese patients with cardiovascular diseases. CYP2D6 genotyping is justifiable in elderly patients to minimize the risk of adverse events and ensure the benefits of metoprolol.

Leveraging large observational studies to discover genetic determinants of drug concentrations: A proof-of-concept study

Large, observational genetic studies are commonly used to identify genetic factors associated with diseases and disease‐related traits. Such cohorts have not been commonly used to identify genetic predictors of drug dosing or concentrations, perhaps because of the heterogeneity in drug dosing and formulation, and the random timing of blood sampling. We hypothesized that large sample sizes relative to traditional pharmacokinetic studies would compensate for this variability and enable the identification of pharmacogenetic predictors of drug concentrations. We performed a cross‐sectional, proof‐of‐concept association study to replicate the well‐established association between metoprolol concentrations and CYP2D6 genotype‐inferred metabolizer phenotypes in participants from the Montreal Heart Institute Hospital Cohort undergoing metoprolol therapy. Plasma concentrations of metoprolol and α‐hydroxymetoprolol (α‐OH‐metoprolol) were measured in samples collected randomly regarding the previous metoprolol dose. A total of 999 individuals were included. The metoprolol daily dose ranged from 6.25 to 400 mg (mean 84.3 ± 57.1 mg). CYP2D6‐inferred phenotype was significantly associated with both metoprolol and α‐OH‐metoprolol in unadjusted and adjusted models (all p < 10⁻¹⁴). Models for metoprolol daily dose showed consistent results. Our study suggests that randomly drawn blood samples from biobanks can serve as a new approach to discover genetic associations related to drug concentrations and dosing, with potentially broader implications for genomewide association studies on the pharmacogenomics of drug metabolism.

Pharmacogenetics to guide cardiovascular drug therapy

Over the past decade, pharmacogenetic testing has emerged in clinical practice to guide selected cardiovascular therapies. The most common implementation in practice is CYP2C19 genotyping to predict clopidogrel response and assist in selecting antiplatelet therapy after percutaneous coronary intervention. Additional examples include genotyping to guide warfarin dosing and statin prescribing. Increasing evidence exists on outcomes with genotype-guided cardiovascular therapies from multiple randomized controlled trials and observational studies. Pharmacogenetic evidence is accumulating for additional cardiovascular medications. However, data for many of these medications are not yet sufficient to support the use of genotyping for drug prescribing. Ultimately, pharmacogenetics might provide a means to individualize drug regimens for complex diseases such as heart failure, in which the treatment armamentarium includes a growing list of medications shown to reduce morbidity and mortality. However, sophisticated analytical approaches are likely to be necessary to dissect the genetic underpinnings of responses to drug combinations. In this Review, we examine the evidence supporting pharmacogenetic testing in cardiovascular medicine, including that available from several clinical trials. In addition, we describe guidelines that support the use of cardiovascular pharmacogenetics, provide examples of clinical implementation of genotype-guided cardiovascular therapies and discuss opportunities for future growth of the field.

Isocyanate derivatization coupled with phospholipid removal microelution-solid phase extraction for the simultaneous quantification of (S)-metoprolol and (S)-α-hydroxymetoprolol in human plasma with LC-MS/MS

A sensitive liquid chromatography-tandem mass spectrometry (LC-MS/MS) assay was developed and validated for the quantification of (S)-metoprolol (MET) and its main metabolite, (S)-α-hydroxymetoprolol (OH-MET). Human plasma samples (50 μL) were spiked with both analytes and their deuterated internal standards (IS) (S)-MET-(d7) and α-OH-MET-(d5). Phospholipid removal microelution-solid phase extraction (PRM-SPE) was performed using a 4-step protocol with Oasis PRiME MCX μElution 96-well cartridges. The eluates were reconstituted in 100 μL of acetonitrile with 50 μg/mL (S)-α-methylbenzyl isocyanate (MBIC) for chiral derivatization. After 60 min at room temperature, the reaction was quenched using 100 μL of water 2 % formic acid. Chromatographic separation of the derivatized analytes was performed on a Kinetex phenyl-hexyl core-shell stationary phase with an elution gradient. Mobile phases were composed of a mixture of water and methanol, with ammonium formate and formic acid as buffers. Total runtime was 15 min. Analyte detection was performed by an AB/SCIEX 4000 QTRAP mass spectrometer with multiple reaction monitoring. Chromatograms showed MBIC successfully reacted with racemic MET, α-OH-MET, and their respective IS. Detection by positive electrospray ionization did not reveal derivatized by-products. Quantification ranges were validated for (S)-MET and (S)-α-OH-MET between 0.5-500 and 1.25-500 ng/mL, respectively, with correlation coefficients (r²) >0.9906. The PRM-SPE assay showed low matrix effects (86.9-104.0 %) and reproducible recoveries (69.4-78.7 %) at low, medium, and high quality control (QC) levels. Precision and accuracy were all comprised between 85-115 % for all three QCs, and between 80-120 % for the lower limit of quantification, for intra- and inter-day values (n = 6, 3 consecutive days). Non-derivatized analytes were stable at room temperature, after 3 freeze-thaw cycles, and stored for 30 days at -80 °C (n = 4). Reinjection reproducibility of a previously validated batch was achieved after 8 days under auto-sampler conditions, indicating the stability of (S)-MET and (S)-α-OH-MET derivatives. Its clinical use was established in a cohort of 50 patients and could be used to further investigate the clinical impact of (S)-MET concentrations.

The Role of Pharmacogenomics in Contemporary Cardiovascular Therapy: A position statement from the European Society of Cardiology Working Group on Cardiovascular Pharmacotherapy

There is a strong and ever-growing body of evidence regarding the use of pharmacogenomics to inform cardiovascular pharmacology. However, there is no common position taken by international cardiovascular societies to unite diverse availability, interpretation and application of such data, nor is there recognition of the challenges of variation in clinical practice between countries within Europe. Aside from the considerable barriers to implementing pharmacogenomic testing and the complexities of clinically actioning results, there are differences in the availability of resources and expertise internationally within Europe. Diverse legal and ethical approaches to genomic testing and clinical therapeutic application also require serious thought. As direct-to-consumer genomic testing becomes more common, it can be anticipated that data may be brought in by patients themselves, which will require critical assessment by the clinical cardiovascular prescriber. In a modern, pluralistic and multi-ethnic Europe, self-identified race/ethnicity may not be concordant with genetically detected ancestry and thus may not accurately convey polymorphism prevalence. Given the broad relevance of pharmacogenomics to areas such as thrombosis and coagulation, interventional cardiology, heart failure, arrhythmias, clinical trials, and policy/regulatory activity within cardiovascular medicine, as well as to genomic and pharmacology subspecialists, this position statement attempts to address these issues at a wide-ranging level.

Pharmacogenomics for Primary Care: An Overview

Most of the prescribing and dispensing of medicines happens in primary care. Pharmacogenomics (PGx) is the study and clinical application of the role of genetic variation on drug response. Mounting evidence suggests PGx can improve the safety and/or efficacy of several medications commonly prescribed in primary care. However, implementation of PGx has generally been limited to a relatively few academic hospital centres, with little adoption in primary care. Despite this, many primary healthcare providers are optimistic about the role of PGx in their future practice. The increasing prevalence of direct-to-consumer genetic testing and primary care PGx studies herald the plausible gradual introduction of PGx into primary care and highlight the changes needed for optimal translation. In this article, the potential utility of PGx in primary care will be explored and on-going barriers to implementation discussed. The evidence base of several drug-gene pairs relevant to primary care will be outlined with a focus on antidepressants, codeine and tramadol, statins, clopidogrel, warfarin, metoprolol and allopurinol. This review is intended to provide both a general introduction to PGx with a more in-depth overview of elements relevant to primary care.

Examination of Metoprolol Pharmacokinetics and Pharmacodynamics Across CYP2D6 Genotype-Derived Activity Scores

Recent CYP2D6 phenotype standardization efforts by CYP2D6 activity score (AS) are based on limited pharmacokinetic (PK) and pharmacodynamic (PD) data. Using data from two independent clinical trials of metoprolol, we compared metoprolol PK and PD across CYP2D6 AS with the goal of determining whether the PK and PD data support the new phenotype classification. S‐metoprolol apparent oral clearance (CLo), adjusted for clinical factors, was correlated with CYP2D6 AS (P < 0.001). The natural log of CLo was lower with an AS of 1 (7.6 ± 0.4 mL/minute) vs. 2–2.25 (8.3 ± 0.6 mL/minute; P = 0.012), similar between an AS of 1 and 1.25–1.5 (7.8 ± 0.5 mL/minute; P = 0.702), and lower with an AS of 1.25–1.5 vs. 2–2.25 (P = 0.03). There was also a greater reduction in heart rate with metoprolol among study participants with AS of 1 (−10.8 ± 5.5) vs. 2–2.25 (−7.1 ± 5.6; P < 0.001) and no significant difference between those with an AS of 1 and 1.25–1.5 (−9.2 ± 4.7; P = 0.095). These data highlight linear trends among CYP2D6 AS and metoprolol PK and PD, but inconsistencies with the phenotypes assigned by AS based on the current standards. Overall, this case study with metoprolol suggests that utilizing CYP2D6 AS, instead of collapsing AS into phenotype categories, may be the most precise approach for utilizing CYP2D6 pharmacogenomics in clinical practice.

Pharmacogenetic factors affecting β-blocker metabolism and response

INTRODUCTION

β-blockers are among the most widely prescribed of all drugs, used for treatment of a large number of cardiovascular diseases. Herein we evaluate literature pertaining to pharmacogenetics of β-blocker therapy, provide insight into the robustness of the genetic associations, and determine the appropriateness for translating these genetic associations into clinical practice.

AREAS COVERED

A literature search was conducted using PubMed to collate evidence on associations between CYP2D6, ADRB1, ADRB2, and GRK5 genetic variation and drug-response outcomes in the presence of β-blocker exposure. Pharmacokinetic, pharmacodynamic, and clinical outcomes studies were included if genotype data and β-blocker exposure were documented.

EXPERT OPINION

Substantial data suggest that specific ADRB1 and GRK5 genotypes are associated with improved β-blocker efficacy and have potential for use to guide therapy decisions in the clinical setting. While the data do not justify ordering a CYP2D6 pharmacogenetic test, if CYP2D6 genotype is available in the electronic health record, there may be clinical utility for understanding dosing of β-blockers.

Prescribed Doses of CYP2D6-Metabolized Drugs and Hemodynamic Responses in Relation to CYP2D6 Genotype Among Older Patients Exposed to Polypharmacy

Background

Many drugs with dose-dependent effects on hemodynamic variables are metabolized by cytochrome P450 2D6 (CYP2D6). The aim of this study was to compare prescribed dosages and hemodynamic responses of such drugs in relation to pharmacogenetic variability in CYP2D6 metabolism among patients aged ≥ 70 years exposed to polypharmacy.

Materials and Methods

We included 173 patients with detailed information about drug use. The patients were retrospectively subjected to CYP2D6 genotyping, which comprised the most common variant alleles encoding reduced, absent, or increased CYP2D6 metabolism. In order to compare dosages across different CYP2D6-metabolized drugs, all prescribed daily doses were harmonized to the ‘percent of a daily defined dose’ (DDD). The mean harmonized DDD was compared between genotype-predicted normal metabolizers (NMs) and patients with reduced or absent CYP2D6 enzyme activity, defined as intermediate or poor metabolizers (IMs/PMs). Blood pressure, pulse, and patient proportions with orthostatism and bradycardia were also compared between genotype subgroups.

Results

The genotype-predicted phenotype subgroups comprised 79 NMs (45.7%), 75 IMs (43.4%), and 16 PMs (9.2%). There were no differences in dosing of CYP2D6 substrates between NMs and IMs/PMs (p = 0.76). A higher proportion of CYP2D6 IMs/PMs experienced orthostatism (p = 0.03), while there were no significant subgroup differences for the other hemodynamic variables.

Conclusion

In this real-life clinical setting of patients aged ≥ 70 years, dosing of CYP2D6 substrates were not adjusted according to genotype-predicted CYP2D6 metabolism. The increased occurrence of orthostatism in patients with reduced/absent CYP2D6 metabolism may indicate that individualized dosing based on genotype has the potential to prevent adverse effects in these vulnerable patients.

Electronic supplementary material

The online version of this article (10.1007/s40266-020-00763-0) contains supplementary material, which is available to authorized users.

CYP2D6 polymorphism and its impact on the clinical response to metoprolol: A systematic review and meta-analysis

AIMS

CYP2D6 genetic polymorphisms are associated with metoprolol pharmacokinetics. Whether the clinical response to metoprolol is also affected remains uncertain.

METHODS

We conducted a systematic review on the effects of CYP2D6 polymorphism on the clinical response to metoprolol. Searches were conducted using MEDLINE. Meta-analyses were performed on the impact of CYP2D6-inferred phenotypes on heart rate (HR) reduction, diastolic (DBP) and systolic (SBP) blood pressure reduction, average daily doses, all-type adverse events and bradycardia.

RESULTS

Our qualitative assessment indicated inconsistent results in individual studies and endpoints, but CYP2D6 poor metabolizers (PM) generally presented a greater reduction in HR. The meta-analysis of 15 studies, including a total of 1146 individuals, found a reduction in HR of 3 beats/min (P = .017), and of SBP and DBP by 3 mmHg (P = .0048) for PM compared to non-PM individuals using similar metoprolol doses. Bradycardia appeared more frequent by 4-fold for PM, although significant heterogeneity was observed regarding bradycardia, which limits the scope of this finding.

CONCLUSION

Patients without any CYP2D6 metabolic capacities appear to have increased reduction in DBP, HR and SBP during metoprolol treatment and may be at a higher risk of bradycardia compared to patients with active CYP2D6 phenotypes. Further prospective data are required to determine whether CYP2D6 is associated with clinical events in patients treated with metoprolol, as well as to demonstrate the clinical utility of an individualized approach of prescribing metoprolol using CYP2D6-inferred phenotypes.

Pharmacological interventions for heart failure in people with chronic kidney disease

BACKGROUND

Approximately half of people with heart failure have chronic kidney disease (CKD). Pharmacological interventions for heart failure in people with CKD have the potential to reduce death (any cause) or hospitalisations for decompensated heart failure. However, these interventions are of uncertain benefit and may increase the risk of harm, such as hypotension and electrolyte abnormalities, in those with CKD.

OBJECTIVES

This review aims to look at the benefits and harms of pharmacological interventions for HF (i.e., antihypertensive agents, inotropes, and agents that may improve the heart performance indirectly) in people with HF and CKD.

SEARCH METHODS

We searched the Cochrane Kidney and Transplant Register of Studies through 12 September 2019 in consultation with an Information Specialist and using search terms relevant to this review. Studies in the Register are identified through searches of CENTRAL, MEDLINE, and EMBASE, conference proceedings, the International Clinical Trials Register (ICTRP) Search Portal and ClinicalTrials.gov.

SELECTION CRITERIA

We included randomised controlled trials of any pharmacological intervention for acute or chronic heart failure, among people of any age with chronic kidney disease of at least three months duration.

DATA COLLECTION AND ANALYSIS

Two authors independently screened the records to identify eligible studies and extracted data on the following dichotomous outcomes: death, hospitalisations, worsening heart failure, worsening kidney function, hyperkalaemia, and hypotension. We used random effects meta-analysis to estimate treatment effects, which we expressed as a risk ratio (RR) with 95% confidence intervals (CI). We assessed the risk of bias using the Cochrane tool. We applied the GRADE methodology to rate the certainty of evidence.

MAIN RESULTS

One hundred and twelve studies met our selection criteria: 15 were studies of adults with CKD; 16 studies were conducted in the general population but provided subgroup data for people with CKD; and 81 studies included individuals with CKD, however, data for this subgroup were not provided. The risk of bias in all 112 studies was frequently high or unclear. Of the 31 studies (23,762 participants) with data on CKD patients, follow-up ranged from three months to five years, and study size ranged from 16 to 2916 participants. In total, 26 studies (19,612 participants) reported disaggregated and extractable data on at least one outcome of interest for our review and were included in our meta-analyses. In acute heart failure, the effects of adenosine A1-receptor antagonists, dopamine, nesiritide, or serelaxin on death, hospitalisations, worsening heart failure or kidney function, hyperkalaemia, hypotension or quality of life were uncertain due to sparse data or were not reported. In chronic heart failure, the effects of angiotensin-converting enzyme inhibitors (ACEi) or angiotensin receptor blockers (ARB) (4 studies, 5003 participants: RR 0.85, 95% CI 0.70 to 1.02; I2 = 78%; low certainty evidence), aldosterone antagonists (2 studies, 34 participants: RR 0.61 95% CI 0.06 to 6.59; very low certainty evidence), and vasopressin receptor antagonists (RR 1.26, 95% CI 0.55 to 2.89; 2 studies, 1840 participants; low certainty evidence) on death (any cause) were uncertain. Treatment with beta-blockers may reduce the risk of death (any cause) (4 studies, 3136 participants: RR 0.69, 95% CI 0.60 to 0.79; I2 = 0%; moderate certainty evidence). Treatment with ACEi or ARB (2 studies, 1368 participants: RR 0.90, 95% CI 0.43 to 1.90; I2 = 97%; very low certainty evidence) had uncertain effects on hospitalisation for heart failure, as treatment estimates were consistent with either benefit or harm. Treatment with beta-blockers may decrease hospitalisation for heart failure (3 studies, 2287 participants: RR 0.67, 95% CI 0.43 to 1.05; I2 = 87%; low certainty evidence). Aldosterone antagonists may increase the risk of hyperkalaemia compared to placebo or no treatment (3 studies, 826 participants: RR 2.91, 95% CI 2.03 to 4.17; I2 = 0%; low certainty evidence). Renin inhibitors had uncertain risks of hyperkalaemia (2 studies, 142 participants: RR 0.86, 95% CI 0.49 to 1.49; I2 = 0%; very low certainty). We were unable to estimate whether treatment with sinus node inhibitors affects the risk of hyperkalaemia, as there were few studies and meta-analysis was not possible. Hyperkalaemia was not reported for the CKD subgroup in studies investigating other therapies. The effects of ACEi or ARB, or aldosterone antagonists on worsening heart failure or kidney function, hypotension, or quality of life were uncertain due to sparse data or were not reported. Effects of anti-arrhythmic agents, digoxin, phosphodiesterase inhibitors, renin inhibitors, sinus node inhibitors, vasodilators, and vasopressin receptor antagonists were very uncertain due to the paucity of studies.

AUTHORS' CONCLUSIONS

The effects of pharmacological interventions for heart failure in people with CKD are uncertain and there is insufficient evidence to inform clinical practice. Study data for treatment outcomes in patients with heart failure and CKD are sparse despite the potential impact of kidney impairment on the benefits and harms of treatment. Future research aimed at analysing existing data in general population HF studies to explore the effect in subgroups of patients with CKD, considering stage of disease, may yield valuable insights for the management of people with HF and CKD.

Impact of genotype-predicted CYP2D6 metabolism on clinical effects and tolerability of metoprolol in patients after myocardial infarction - a prospective observational study

PURPOSE

The β-1 adrenergic receptor blocker metoprolol is primarily metabolized by the polymorphic enzyme cytochrome P 450 2D6 (CYP2D6), an enzyme with substantial genetic heterogeneity. Our purpose was to investigate the impact of CYP2D6 metabolism on clinical effects and tolerability of metoprolol in patients after myocardial infarction (MI).

METHODS

We included 136 patients with MI discharged on treatment with metoprolol with a recommendation to the general practitioner (GP) to increase the metoprolol dose up to 200 mg/day within 2 months if possible. At follow-up, metoprolol dosage after up-titration, metoprolol steady-state trough plasma concentrations, hemodynamic parameters, potential metoprolol-induced adverse drug reactions and number of visits to the GP were measured. CYP2D6 genotyping including the reduced-function variant alleles CYP2D6*9, CYP2D6*10 and CYP2D6*41 was performed after end of follow-up.

RESULTS

According to the genotype-defined CYP2D6 phenotypes, 30% of the patients were metoprolol extensive metabolizers (EMs), 55% intermediate metabolizers (IMs) and 13% poor metabolizers (PMs; carriers of non-coding and reduced-function variant included). Dose-adjusted metoprolol trough concentrations were significantly higher in IM (2-fold) and PM (6.2-fold) groups vs. the EM group (p < 0.001). Only 35% of patients in the PM group achieved the primary end point, i.e. reaching at least 85% of the expected maximum heart rate (HR) during exercise, compared with 78% in the EM group (p < 0.01), and maximum observed HR at exercise was significantly lower in the PM group vs. the EM group (129 ± 5 vs. 142 ± 2 bpm, p < 0.007). In contrast, metoprolol maintenance dose, blood pressure, exercise capacity, number of visits at the GP and frequency and severity of self-reported potential metoprolol-related adverse drug reactions were not significantly different between the groups.

CONCLUSION

Using a comprehensive CYP2D6 genotyping panel, the present study demonstrates a > 6-fold increase of dose-adjusted plasma metoprolol trough concentration in CYP2D6 PMs vs. EMs with a parallel lower increase in achieved maximum HR during exercise but without association between genotype and frequency or severity of self-reported adverse drug effects. This may indicate that CYP2D6 PMs potentially could benefit of the increased plasma concentration per dose in a naturalistic setting.

The effect of the CYP2D6 genotype on the maintenance dose of metoprolol in a chronic Dutch patient population

Metoprolol is among the most frequently prescribed β-blockers for the treatment of various cardiovascular diseases. Genetic polymorphism within CYP2D6 has been shown to affect the rate of metabolism of metoprolol. Whether metoprolol dose adjustments are indicated in CYP2D6 poor metabolizers (PMs) has thus far not well been studied. The aim of this study was to determine the effect of the CYP2D6 genotype on the metoprolol maintenance dose in a chronic Dutch patient population. Patients were included if they were treated with metoprolol and in whom CYP2D6 genotype status was known. Patient and treatment characteristics were obtained retrospectively from the electronic healthcare records. Metoprolol maintenance dose was the primary endpoint and was defined as the last known dose that the patients had been treated with. Genotype data were categorized into four phenotypes, that is, PMs, intermediate metabolizers, extensive metabolizers, and ultra-rapid metabolizers (UMs). The endpoints were analyzed as PM versus non-PM. A total of 105 patients were included. The mean ± SD maintenance dose in PMs (n = 12) was significantly lower compared with non-PMs (n = 93), that is, 48 ± 20 versus 84 ± 53 mg, respectively (P = 0.019). No association of the CYP2D6 genotype with the incidence of side effects was observed, although there was a trend for increased risk of drowsiness (P = 0.053). The results of this study show that the CYP2D6 genotype is associated with the maintenance dose of metoprolol. Patients with the CYP2D6 PM phenotype may benefit from a lower metoprolol starting dose, followed by further dose titration to provide patient-tailored therapy and thereby increase the effectiveness of treatment.

[Effects of CYP2D6*10 on plasma trough concentration of metoprolol in patients with coronary artery disease]

OBJECTIVE

To study the effect of CYP2D6^*10 (c.100 C&gt;T) on plasma trough concentrations of metoprolol and its metabolite α-hydroxy metoprolol, blood pressure and heart rate in patients with coronary artery disease.

METHODS

The patients with coronary artery disease taking metoprolol tablets (n=128) and those taking metoprolol sustained-release tablets (n=126) were genotyped for CYP2D6^*10 using Taqman real-time quantitative PCR. The trough concentrations of metoprolol and α-hydroxy metoprolol were determined with UPLC-MS/MS, and the dose-normalized concentrations (C/D) were compared among the patients with different CYP2D6^*10 genotypes in both groups. Resting blood pressure and heart rate were recorded in all the patients when the concentration of metoprolol reached the steady state and were compared among the patients with different genotypes.

RESULTS

In patients taking metoprolol sustained-release tablets, the plasma trough concentration of α-hydroxy metoprolol was significantly associated with the systolic blood pressure (P=0.0204). The CYP2D6^*10 poor metabolizers showed a significant association with the C/D of metoprolol and α-hydroxy metoprolol (P &lt; 0.01) in patients receiving metoprolol in both formulations, and in both groups, the C/D of metoprolol was significantly higher in the patients with a TT genotype than in those with a CC or CT genotype (P &lt; 0.01); compared with those with the CT genotype, the patients with the TT genotype had a significantly lower C/D of α-hydroxy metoprolol (P &lt; 0.01). In patients taking metoprolol sustained-release tablets, those with the CT (P=0.0281) and TT (P=0.0196) genotypes had lower diastolic blood pressure than patients with the CC genotypes, but the systolic blood pressure or heart rate did not differ significantly among them.

CONCLUSIONS

CYP2D6^*10T allele mutation can reduce the metabolism of metoprolol, increase the C/D of metoprolol and decrease the C/D of α-metoprolol and diastolic blood pressure in patients with coronary artery disease, but CYP2D6^*10 variation does not significantly affect systolic blood pressure or heart rate in the patients when the concentration of metoprolol reaches a steady state.

Genetic Variation of Hepatic Enzymes Influence on β-Blocker Dose in Patients With Reduced Ejection Fraction Heart Failure

Beta-blockers such as metoprolol, carvedilol, and bisoprolol are indicated for the treatment of patients with reduced ejection fraction heart failure. Heart failure treatment guidelines call for titration of these medications to specific target doses for morbidity and mortality benefit. Hepatic enzymes are responsible for metabolizing these medications; however, these enzymes are subject to genetic variations (polymorphisms) that can increase or decrease enzyme activity. Metoprolol relies almost exclusively on this enzyme for degradation to inactive metabolites, whereas carvedilol relies on this enzyme only partially for metabolism, and the portion of drug that is metabolized by CYP2D6 becomes active metabolites. The clinical significance of genetic variations in CYP2D6 in heart failure patients requiring treatment with carvedilol and metoprolol remains unclear, and further research is needed before any strong recommendations on treatment approach can be made. However, based on what is known regarding the incidence of genetic variations of this enzyme, it is reasonable to conclude that heart failure patients of European and Asian ancestry may be at a greater risk of intolerance to guideline-directed doses of metoprolol. Patients of North African ancestry may be at a lower risk of intolerance to metoprolol, although limited data are available to conclude. Additionally, due to the significant prevalence of CYP2D6 enzyme variations among all ethnicities, it may be reasonable to consider switching to carvedilol for patients who are unable to fully titrate metoprolol.

[Pharmacokinetic risk factors of beta-blockers overdose in the elderly: Case report and pharmacology approach]

Beta-blockers are widely prescribed in elderly patients and may induce severe adverse drug reactions. We report a case of bisoprolol-induced bradycardia in an elderly patient with impaired renal function and use of cytochrome P450 inhibitors. A literature review has been performed in order to analyze pharmacokinetic risk factors of beta-blockers overdosing in geriatrics. Various mechanisms can result in decreased elimination of beta-blockers. These mechanisms vary according to the beta-blocker agent and may be combined in some individuals, especially elderly patients. This can lead to unexpected overexposure. Knowledge about drug interactions and pharmacokinetic elimination pathways is important for preventing overexposure and adverse drug reactions when using beta-blockers.

CYP2D6 Genetic Variation and Beta-Blocker Maintenance Dose in Patients with Heart Failure

PURPOSE

This study examined whether a CYP2D6 polymorphism (CYP2D6*4) was related to beta-blocker maintenance dose in patients with heart failure.

METHODS

Logistic regression modeling was utilized in a retrospective chart-review analysis of heart-failure patients (60% Male, 90% of European descent) to assess whether CYP2D6*4 (non-functional CYP2D6 allele present in 1 of 5 individuals of European descent) is associated with maintenance dose of carvedilol (n = 65) or metoprolol (n = 33).

RESULTS

CYP2D6*4 was associated with lower maintenance dose of metoprolol (OR 0.13 [95% CI 0.02-0.75] p = 0.023), and a trend was observed between CYP2D6*4 and higher maintenance dose of carvedilol (OR 2.94 [95% CI 0.84-10.30] p = 0.093). None of the patients that carried CYP2D6*4 achieved the recommended target dose of metoprolol (200 mg/day).

CONCLUSION

Consistent with the role of CYP2D6 in the metabolism of metoprolol, the tolerated maintenance dose of metoprolol was lower in CYP2D6*4 carriers compared to non-carriers. Consistent with the role of CYP2D6 in activation of carvedilol, tolerated maintenance dose of carvedilol was higher in CYP2D6*4 carriers compared to non-carriers. Further investigation is warranted to ascertain the potential of CYP2D6 as a potential predictive biomarker of beta-blocker maintenance dose in heart failure patients.

Pharmacogenomics of heart failure: a systematic review

BACKGROUND

Heart failure (HF) and multiple HF-related phenotypes are heritable. Genes implicated in the HF pathophysiology would be expected to influence the response to treatment.

METHODS

We conducted a series of systematic literature searches on the pharmacogenetics of HF therapy to assess the current knowledge on this field.

RESULTS

Existing data related to HF pharmacogenomics are still limited. The ADRB1 gene is a likely candidate to predict response to β-blockers. Moreover, the cytochrome P450 2D6 coding gene (CYP2D6) clearly affects the pharmacokinetics of metoprolol, although the clinical impact of this association remains to be established.

CONCLUSION

Given the rising prevalence of HF and related costs, a more personalized use of HF drugs could have a remarkable benefit for patients, caregivers and healthcare systems.

Cardiovascular Pharmacogenomics--Implications for Patients With CKD

CKD is an independent risk factor for cardiovascular disease (CVD). Thus, patients with CKD often require treatment with cardiovascular drugs, such as antiplatelet, antihypertensive, anticoagulant, and lipid-lowering agents. There is significant interpatient variability in response to cardiovascular therapies, which contributes to risk for treatment failure or adverse drug effects. Pharmacogenomics offers the potential to optimize cardiovascular pharmacotherapy and improve outcomes in patients with CVD, although data in patients with concomitant CKD are limited. The drugs with the most pharmacogenomic evidence are warfarin, clopidogrel, and statins. There are also accumulating data for genetic contributions to β-blocker response. Guidelines are now available to assist with applying pharmacogenetic test results to optimize warfarin dosing, selection of antiplatelet therapy after percutaneous coronary intervention, and prediction of risk for statin-induced myopathy. Clinical data, such as age, body size, and kidney function have long been used to optimize drug prescribing. An increasing number of institutions are also implementing genetic testing to be considered in the context of important clinical factors to further personalize drug therapy for patients with CVD.

Factors affecting the development of adverse drug reactions to β-blockers in hospitalized cardiac patient population

The aim of the present study was to undertake a study on the prevalence of cytochrome P450 2D6 (CYP2D6) poor metabolizer alleles (*3, *4, *5, and *6) on a Montenegrin population and its impact on developing adverse drug reactions (ADRs) of β-blockers in a hospitalized cardiac patient population. A prospective study was conducted in the Cardiology Center of the Clinical Center of Montenegro and included 138 patients who had received any β-blocker in their therapy. ADRs were collected using a specially designed questionnaire, based on the symptom list and any signs that could point to eventual ADRs. Data from patients' medical charts, laboratory tests, and other available parameters were observed and combined with the data from the questionnaire. ADRs to β-blockers were observed in 15 (10.9%) patients. There was a statistically significant difference in the frequency of ADRs in relation to genetically determined enzymatic activity (P<0.001), with ADRs' occurrence significantly correlating with slower CYP2D6 metabolism. Our study showed that the adverse reactions to β-blockers could be predicted by the length of hospitalization, CYP2D6 poor metabolizer phenotype, and the concomitant use of other CYP2D6-metabolizing drugs. Therefore, in hospitalized patients with polypharmacy CYP2D6 genotyping might be useful in detecting those at risk of ADRs.

Where Failure Is Not an Option -Personalized Medicine in Astronauts

Drug safety and efficacy are highly variable among patients. Most patients will experience the desired drug effect, but some may suffer from adverse drug reactions or gain no benefit. Pharmacogenetic testing serves as a pre-treatment diagnostic option in situations where failure or adverse events should be avoided at all costs. One such situation is human space flight. On the international space station (ISS), a list of drugs is available to cover typical emergency settings, as well as the long-term treatment of common conditions for the use in self-medicating common ailments developing over a definite period. Here, we scrutinized the list of the 78 drugs permanently available at the ISS (year 2014) to determine the extent to which their metabolism may be affected by genetic polymorphisms, potentially requiring genotype-specific dosing or choice of an alternative drug. The purpose of this analysis was to estimate the potential benefit of pharmacogenetic diagnostics in astronauts to prevent therapy failure or side effects.

Interpretation of mRNA splicing mutations in genetic disease: review of the literature and guidelines for information-theoretical analysis

The interpretation of genomic variants has become one of the paramount challenges in the post-genome sequencing era. In this review we summarize nearly 20 years of research on the applications of information theory (IT) to interpret coding and non-coding mutations that alter mRNA splicing in rare and common diseases. We compile and summarize the spectrum of published variants analyzed by IT, to provide a broad perspective of the distribution of deleterious natural and cryptic splice site variants detected, as well as those affecting splicing regulatory sequences. Results for natural splice site mutations can be interrogated dynamically with Splicing Mutation Calculator, a companion software program that computes changes in information content for any splice site substitution, linked to corresponding publications containing these mutations. The accuracy of IT-based analysis was assessed in the context of experimentally validated mutations. Because splice site information quantifies binding affinity, IT-based analyses can discern the differences between variants that account for the observed reduced (leaky) versus abolished mRNA splicing. We extend this principle by comparing predicted mutations in natural, cryptic, and regulatory splice sites with observed deleterious phenotypic and benign effects. Our analysis of 1727 variants revealed a number of general principles useful for ensuring portability of these analyses and accurate input and interpretation of mutations. We offer guidelines for optimal use of IT software for interpretation of mRNA splicing mutations.

Interpretation of mRNA splicing mutations in genetic disease: review of the literature and guidelines for information-theoretical analysis

The interpretation of genomic variants has become one of the paramount challenges in the post-genome sequencing era. In this review we summarize nearly 20 years of research on the applications of information theory (IT) to interpret coding and non-coding mutations that alter mRNA splicing in rare and common diseases. We compile and summarize the spectrum of published variants analyzed by IT, to provide a broad perspective of the distribution of deleterious natural and cryptic splice site variants detected, as well as those affecting splicing regulatory sequences. Results for natural splice site mutations can be interrogated dynamically with Splicing Mutation Calculator, a companion software program that computes changes in information content for any splice site substitution, linked to corresponding publications containing these mutations. The accuracy of IT-based analysis was assessed in the context of experimentally validated mutations. Because splice site information quantifies binding affinity, IT-based analyses can discern the differences between variants that account for the observed reduced (leaky) versus abolished mRNA splicing. We extend this principle by comparing predicted mutations in natural, cryptic, and regulatory splice sites with observed deleterious phenotypic and benign effects. Our analysis of 1727 variants revealed a number of general principles useful for ensuring portability of these analyses and accurate input and interpretation of mutations. We offer guidelines for optimal use of IT software for interpretation of mRNA splicing mutations.

G protein-coupled receptor kinase 5 gene polymorphisms are associated with postoperative atrial fibrillation after coronary artery bypass grafting in patients receiving β-blockers

BACKGROUND

We hypothesized that genetic variations in the adrenergic signaling pathway and cytochrome P450 2D6 enzyme are associated with new-onset atrial fibrillation (AF) in patients who underwent coronary artery bypass grafting and were treated with perioperative β-blockers (BBs).

METHODS AND RESULTS

Two cohorts of patients who underwent coronary artery bypass grafting and received perioperative BBs at Duke University Medical Center were studied. In a discovery cohort of 563 individuals from the Perioperative Genetics and Safety Outcomes Study (PEGASUS), using a covariate-adjusted logistic regression analysis, we tested 492 single-nucleotide polymorphisms (SNPs) in 10 candidate genes of the adrenergic signaling pathway and cytochrome P450 2D6 for association with postoperative AF despite perioperative BB therapy. SNPs meeting a false discovery rate ≤0.20 (P<0.002) were then tested in the replication cohort of 245 individuals from the Catheterization Genetics biorepository. Of the 492 SNPs examined, 4 intronic SNPs of the G protein-coupled kinase 5 (GRK5) gene were significantly associated with postoperative AF despite perioperative BB therapy in the discovery cohort with additive odds ratios between 1.72 and 2.75 (P=4.78×10(-5) to 0.0015). Three of these SNPs met nominal significance levels in the replication cohort with odds ratios between 2.07 and 2.60 (P=0.007 to 0.016). However, meta-analysis of the 2 data sets cohorts suggested strong association with postoperative AF despite perioperative BB therapy in all 4 SNPs (meta-P values from 1.66×10(-6) to 3.39×10(-5)).

CONCLUSIONS

In patients undergoing coronary artery bypass grafting, genetic variation in GRK5 is associated with postoperative AF despite perioperative BB therapy.