Oral anticoagulants in the elderly

Organ-differential Roles of Akt/FoxOs Axis as a Key Metabolic Modulator during Aging

FoxOs and their post-translational modification by phosphorylation, acetylation, and methylation can affect epigenetic modifications and promote the expression of downstream target genes. Therefore, they ultimately affect cellular and biological functions during aging or occurrence of age-related diseases including cancer, diabetes, and kidney diseases. As known for its key role in aging, FoxOs play various biological roles in the aging process by regulating reactive oxygen species, lipid accumulation, and inflammation. FoxOs regulated by PI3K/Akt pathway modulate the expression of various target genes encoding MnSOD, catalases, PPARγ, and IL-1β during aging, which are associated with age-related diseases. This review highlights the age-dependent differential regulatory mechanism of Akt/FoxOs axis in metabolic and non-metabolic organs. We demonstrated that age-dependent suppression of Akt increases the activity of FoxOs (Akt/FoxOs axis upregulation) in metabolic organs such as liver and muscle. This Akt/FoxOs axis could be modulated and reversed by antiaging paradigm calorie restriction (CR). In contrast, hyperinsulinemia-mediated PI3K/Akt activation inhibited FoxOs activity (Akt/FoxOs axis downregulation) leading to decrease of antioxidant genes expression in non-metabolic organs such as kidneys and lungs during aging. These phenomena are reversed by CR. The results of studies on the process of aging and CR indicate that the Akt/FoxOs axis plays a critical role in regulating metabolic homeostasis, redox stress, and inflammation in various organs during aging process. The benefical actions of CR on the Akt/FoxOs axis in metabolic and non-metabolic organs provide further insights into the molecular mechanisms of organ-differential roles of Akt/FoxOs axis during aging.

Influence of Renal Impairment and Genetic Subtypes on Warfarin Control in Japanese Patients

The genotypes of vitamin K epoxide reductase complex 1 (VKORC1) and cytochrome P450 2C9 (CYP2C9) can influence therapeutic warfarin doses. Conversely, nongenetic factors, especially renal function, are associated with warfarin maintenance doses; however, the optimal algorithm for considering genes and renal dysfunction has not been established. This single-center prospective cohort study aimed to evaluate the factors affecting warfarin maintenance doses and develop pharmacogenetics-guided algorithms, including the factors of renal impairment and others. To commence, 176 outpatients who were prescribed warfarin for thromboembolic stroke prophylaxis in the stroke center, were enrolled. Patient characteristics, blood test results, dietary vitamin K intake, and CYP2C9 and VKORC1 (-1639G>A) genotypes were recorded. CYP2C9 and VKORC1 (-1639G>A) genotyping revealed that 80% of the patients had CYP2C9 *1/*1 and VKORC1 mutant AA genotypes. Multiple linear regression analysis demonstrated that the optimal pharmacogenetics-based model comprised age, body surface area, estimated glomerular filtration rate (eGFR), genotypes, vitamin K intake, aspartate aminotransferase levels, and alcohol intake. eGFR exercised a significant impact on the maintenance doses, as an increase in eGFR of 10 mL/min/1.73 m² escalated the warfarin maintenance dose by 0.6 mg. Reduced eGFR was related to lower warfarin maintenance doses, independent of VKORC1 and CYP2C9 genotypes in Japanese patients.

Heterogeneity in treatment effects across diverse populations

Differences in patient characteristics, including age, sex, and race influence the safety and effectiveness of drugs, biologic products, and medical devices. Here we provide a summary of the topics discussed during the opening panel at the 2018 Johns Hopkins Center for Excellence in Regulatory Science and Innovation symposium on Assessing and Communicating Heterogeneity of Treatment Effects for Patient Subpopulations: Challenges and Opportunities. The goal of this session was to provide a brief overview of FDA-regulated therapeutics, including drugs, biologics and medical devices, and some of the major sources of heterogeneity of treatment effects (HTE) related to patient demographics, such as age, sex and race. The panel discussed the US Food and Drug Administration's role in reviewing and regulating drugs, devices, and biologic products and the challenges associated with ensuring that diverse patient populations benefit from these therapeutics. Ultimately, ensuring diverse demographic inclusion in clinical trials, and designing basic and clinical research studies to account for the intended patient population's age, sex, race, and genetic factors among other characteristics, will lead to better, safer therapies for diverse patient populations.

Risk of over-anticoagulation during acute kidney injury in patients treated with vitamin K antagonists

Background

Vitamin K antagonists (VKAs) are still in use for oral anticoagulation, but not all indications allow their replacement by direct oral anticoagulants. Although formal dose reduction is not required in patients with impaired kidney function, case reports indicate that acute kidney injury (AKI) might be associated with derailment of VKA therapy.

Methods

The study retrospectively collected patients from a tertiary nephrology care centre who experienced AKI while being treated with VKA. In these individuals, the international normalized ratio (INR) as a measure of anticoagulant effect during renal failure was compared with a reference time point with stable kidney function.

Results

A total of 100 patients with AKI and ongoing VKA therapy met the inclusion criteria. The majority (76%) of patients had AKI with CKD. Volume depletion (n = 43), septic renal failure (n = 22), decompensated heart failure (n = 18) and toxic renal damage (n = 11) were the most important causes of AKI. The average INR values at the time of AKI were higher than at the reference time point [median 3.17 (range 1.10–13.0) versus 2.24 (1.07–5.17); P < 0.0001]. Fifty-four patients had INR values above the recommended therapeutic range for their indication at the time point of AKI. Bleeding complications occurred in 24 patients during AKI and the VKA dose had to be reduced in 55. Women, patients with low body mass index and patients with diabetes were predisposed to overanticoagulation during AKI.

Conclusions

The effect of AKI on anticoagulation by VKA has not been systematically described. This risk should be considered in patients at high risk for AKI.

Assessment of agreement and time in therapeutic range of capillary versus venous international normalised ratio in frail elderly people in a nursing home

Vitamin K antagonists are widely used, yet have a slim therapeutic margin and high iatrogenicity. Patients are monitored through international normalised ratio (INR) by venipuncture, but coagulometers could measure INR by capillary puncture. This prospective study evaluated the clinical concordance of capillary INR versus venous INR in 31 nursing home patients. Concordance was good and mean time in therapeutic range (TTR) markedly increased. Capillary INR is thus reliable, could improve TTR and decrease iatrogenicity.

[Treatment with oral anticoagulants in older patients: Should warfarin still be prescribed?]

Vitamin-K antagonists (VKA) have been the standard for oral anticoagulation. However, they carry several problems in older patients: frequent bleeding complications, complex management, risk of interactions with multiple drugs. Two classes of direct oral anticoagulants (DOA) are currently available in France: (a) direct thrombin inhibitors: dabigatran; and (b) direct factor Xa inhibitors: rivaroxaban, apixaban and others. Their management is easier: quickly effective after administration, they are given at fixed doses and do not need regular laboratory monitoring. Several randomized trials have shown that DOA are non-inferior to VKA for treating venous thromboembolic disease (prophylactic or curative treatment) and atrial fibrillation (prevention of associated embolisms). DOA might be also effective for long-term treatment of coronary disease, in some cases. No trial has specifically studied older patients. In the context of atrial fibrillation, subgroup analysis show similar results between patients above and below 75-years-old. Lower doses of dabigatran and apixaban should be used in many older people. All DOA are eliminated at least partly by kidneys. Their dose must be reduced in moderate renal failure (filtration glomerular rate (FGR) 30 to 50mL/min) and they are contraindicated in older patients with severe renal failure (FGR<30mL/min). DOA also have other problems: (a) important drug interactions are still possible, (b) the clinical application of specific coagulation tests need to be defined, (c) their safety in some subgroups of elderly patients, very different from patients included in clinical trials, is not known.

Impact of incorporating ABCB1 and CYP4F2 polymorphisms in a pharmacogenetics-guided warfarin dosing algorithm for the Brazilian population

PURPOSE

Interpatient variation of warfarin dose requirements may be explained by genetic variations and general and clinical factors. In this scenario, diverse population-calibrated dosing algorithms, which incorporate the main warfarin dosing influencers, have been widely proposed for predicting supposed warfarin maintenance dose, in order to prevent and reduce adverse events. The aim of the present study was to evaluate the impact of the inclusion of ABCB1 c.3435C>T and CYP4F2 c.1297G>A polymorphisms as additional covariates in a previously developed pharmacogenetic-based warfarin dosing algorithm calibrated for the Brazilian population.

METHODS

Two independent cohorts of patients treated with warfarin (n = 832 and n = 133) were included for derivation and replication of the algorithm, respectively. Genotyping of ABCB1 c.3435C>T and CYP4F2 c.1297G>A polymorphisms was performed by polymerase chain reaction followed by melting curve analysis and TaqMan® assay, respectively. A multiple linear regression was performed for the warfarin stable doses as a dependent variable, considering clinical, general, and genetic data as covariates.

RESULTS

The inclusion of ABCB1 and CYP4F2 polymorphisms was able to improve the algorithm's coefficient of determination (R²) by 2.6%. In addition, the partial determination coefficients of these variants revealed that they explained 3.6% of the warfarin dose variability. We also observed a marginal improvement of the linear correlation between observed and predicted doses (from 59.7 to 61.4%).

CONCLUSION

Although our study indicates that the contribution of the combined ABCB1 and CYP4F2 genotypes in explaining the overall variability in warfarin dose is not very large, we demonstrated that these pharmacogenomic data are statistically significant. However, the clinical relevance and cost-effective impact of incorporating additional variants in warfarin dosing algorithms should be carefully evaluated.

Mitochondria and Reactive Oxygen Species in Aging and Age-Related Diseases

Aging has been linked to several degenerative processes that, through the accumulation of molecular and cellular damage, can progressively lead to cell dysfunction and organ failure. Human aging is linked with a higher risk for individuals to develop cancer, neurodegenerative, cardiovascular, and metabolic disorders. The understanding of the molecular basis of aging and associated diseases has been one major challenge of scientific research over the last decades. Mitochondria, the center of oxidative metabolism and principal site of reactive oxygen species (ROS) production, are crucial both in health and in pathogenesis of many diseases. Redox signaling is important for the modulation of cell functions and several studies indicate a dual role for ROS in cell physiology. In fact, high concentrations of ROS are pathogenic and can cause severe damage to cell and organelle membranes, DNA, and proteins. On the other hand, moderate amounts of ROS are essential for the maintenance of several biological processes, including gene expression. In this review, we provide an update regarding the key roles of ROS-mitochondria cross talk in different fundamental physiological or pathological situations accompanying aging and highlighting that mitochondrial ROS may be a decisive target in clinical practice.

Molecular and physiological manifestations and measurement of aging in humans

Biological aging is associated with a reduction in the reparative and regenerative potential in tissues and organs. This reduction manifests as a decreased physiological reserve in response to stress (termed homeostenosis) and a time‐dependent failure of complex molecular mechanisms that cumulatively create disorder. Aging inevitably occurs with time in all organisms and emerges on a molecular, cellular, organ, and organismal level with genetic, epigenetic, and environmental modulators. Individuals with the same chronological age exhibit differential trajectories of age‐related decline, and it follows that we should assess biological age distinctly from chronological age. In this review, we outline mechanisms of aging with attention to well‐described molecular and cellular hallmarks and discuss physiological changes of aging at the organ‐system level. We suggest methods to measure aging with attention to both molecular biology (e.g., telomere length and epigenetic marks) and physiological function (e.g., lung function and echocardiographic measurements). Finally, we propose a framework to integrate these molecular and physiological data into a composite score that measures biological aging in humans. Understanding the molecular and physiological phenomena that drive the complex and multifactorial processes underlying the variable pace of biological aging in humans will inform how researchers assess and investigate health and disease over the life course. This composite biological age score could be of use to researchers seeking to characterize normal, accelerated, and exceptionally successful aging as well as to assess the effect of interventions aimed at modulating human aging.

Factors influencing warfarin response in hospitalized patients

The objective of this study was to investigate the influence of simultaneous factors that potentially keep patients far from achieving target INR range at discharge in hospitalized patients. Prospective cross-sectional observational study conducted at the Cardiology Department and Intensive Care Unit (ICU) of the Assiut University Hospitals. One-hundred and twenty patients were enrolled in the study from July 2013 to January 2014. Outcome measures were discharge INRs, bleeding and thromboembolic episodes. Bivariate analysis and multinomial logistic regression were conducted to determine independent risk factors that can keep patients outside target INR range.

Patients who were newly initiated warfarin on hospital admission were given low initiation dose (2.8 mg ± 0.9). They were more likely to have INR values below 1.5 during hospital stay, 13 (27.7%) patients compared with 9 (12.3%) previously treated patients, respectively (p = .034). We found that the best predictors of achieving below target INR range relative to within target INR range were; shorter hospital stay periods (OR, 0.82 for every day increase [95% CI, 0.72–0.94]), being a male patient (OR, 2.86 [95% CI, 1.05–7.69]), concurrent infection (OR, 0.21 [95% CI, 0.07–0.59]) and new initiation of warfarin therapy on hospital admission (OR, 3.73 [95% CI, 1.28–10.9]).

Gender, new initiation of warfarin therapy on hospital admission, shorter hospital stay periods and concurrent infection can have a significant effect on discharge INRs. Initiation of warfarin without giving loading doses increases the risk of having INRs below 1.5 during hospital stay and increases the likelihood of a patient to be discharged with INR below target range. Following warfarin dosing nomograms and careful monitoring of the effect of various factors on warfarin response should be greatly considered.

Benefit of warfarin compared with aspirin in patients with heart failure in sinus rhythm: a subgroup analysis of WARCEF, a randomized controlled trial

BACKGROUND

The Warfarin versus Aspirin in Reduced Cardiac Ejection Fraction (WARCEF) trial found no difference in the primary outcome between warfarin and aspirin in 2305 patients with reduced left ventricular ejection fraction in sinus rhythm. However, it is unknown whether any subgroups benefit from warfarin or aspirin.

METHODS AND RESULTS

We used a Cox model stepwise selection procedure to identify subgroups that may benefit from warfarin or aspirin on the WARCEF primary outcome. A secondary analysis added major hemorrhage to the outcome. The primary efficacy outcome was time to the first to occur of ischemic stroke, intracerebral hemorrhage, or death. Only age group was a significant treatment effect modifier (P for interaction, 0.003). Younger patients benefited from warfarin over aspirin on the primary outcome (4.81 versus 6.76 events per 100 patient-years: hazard ratio, 0.63; 95% confidence interval, 0.48-0.84; P=0.001). In older patients, therapies did not differ (9.91 versus 9.01 events per 100 patient-years: hazard ratio, 1.09; 95% confidence interval, 0.88-1.35; P=0.44). With major hemorrhage added, in younger patients the event rate remained lower for warfarin than aspirin (5.41 versus 7.25 per 100 patient-years: hazard ratio, 0.68; 95% confidence interval, 0.52-0.89; P=0.005), but in older patients it became significantly higher for warfarin (11.80 versus 9.35 per 100 patient-years: hazard ratio, 1.25; 95% confidence interval, 1.02-1.53; P=0.03).

CONCLUSIONS

In patients <60 years, warfarin improved outcomes over aspirin with or without inclusion of major hemorrhage. In patients ≥60 years, there was no treatment difference, but the aspirin group had significantly better outcomes when major hemorrhage was included.

Vitamin K antagonist use in the elderly: special considerations

As the population ages, the number of patients aged 75 years and over treated with vitamin K antagonists (VKAs) is steadily increasing. In this age group, the two main indications for oral anticoagulant therapy are the treatment of venous thromboembolic disease and the prevention of systemic embolism in patients with nonvalvular atrial fibrillation. In both indications, a target international normalized ratio of 2.5 (range: 2.0-3.0) is recommended. Although VKAs are beneficial in thromboembolic disorders, they are still underused. In this review, we will focus on two crucial topics in elderly patients, the specific management of VKAs in these patients and the hemorrhagic risk. Current recommendations concerning the management at the start of treatment, education and adequate monitoring may help to minimize the hemorrhagic risk in these frail patients.

Predisposing Preventable Factors in Patients With Bleeding due to Warfarin Usage: Evaluation of 114 Patients

Warfarin is one of the commonly used oral anticoagulant. The aim of our study is to evaluate the predisposing preventable factors among patients with bleeding due to warfarin usage. This study was performed on 114 cases who were admitted to emergency service for bleeding and whose ages range between 27 and 89 years. The mean time between the onset of the bleeding and admission to the hospital was 2.9 ± 3.4 days. The mean dose of warfarin being used at the time of admission was 31.2 ± 10.8 mg weekly. Only 37 cases were being controlled regularly. The mean number of the drugs being used other than warfarin was 4.8 ± 2.5 drugs. Forty-eight cases were using aspirin, 28 nonsteroidal anti-inflammatory drugs other than aspirin and 18 cases were using various antibiotics. Forty eight patients knew that they had to use this drug under the regular follow-up of a physician and 43 knew that during monitoring a laboratory test had to be done while using the drug named as warfarin. Only 39 patients knew that this drug may cause bleeding. It was also surprising that only 9 patients knew that there may be drug interaction and 1 knew that this drug may be affected from the dietary factors. As a result, it may be concluded that most of the patients admitting to the emergency service had a lack of basic knowledge about this drug, which might invite bleeding.

Excessive prolongation of prothrombin time among patients treated with warfarin and admitted to the emergency room

INTRODUCTION

Patients treated with warfarin are uncommonly admitted with excessive prolongation of international normalized ratio (INR) of prothrombin time (PT) to the emergency room (ER). Here we wanted to evaluate the reasons behind this prolongation, clinical and laboratory parameters, course and outcome of these patients.

PATIENTS AND METHODS

Consecutive patients admitted to the ER with prolonged PT-INR>6 under warfarin treatment and who gave sufficient information regarding history of warfarin treatment, were followed prospectively. Patients or care-givers were asked about warfarin treatment, PT monitoring, current and new medications especially antibiotics and diet. Clinical and laboratory parameters, course and outcome were also documented. Age and gender matched patients with therapeutic INR level were used as a control group.

RESULTS

75 patients finished the study. The median INR level among the patients was 8.5 and a range of 6.1-59.5. The median duration of warfarin treatment was 12 months among the patients vs. 36 in the control group, p<0.001 and family physician was the sole decider on warfarin dose in 71 patients vs. 49 in the control group, p<0.100. 19 patients adhered to balanced diet vs. 34 in the control group, p=0.01. Dose increment of warfarin was the most common definite cause of prolonged PT followed by adding new medication especially amiodarone and recently started warfarin. Significantly more patients had evidence of bleeding than the control group but no difference in mean hemoglobin level or number of patients transfused with packed cells. No difference in the number of patients hospitalized or duration of hospitalization, but 5 in-hospital fatalities in the patients' group vs. none in the control group.

CONCLUSION

Excessive PT prolongation is mainly due to warfarin dose increment, adding new medication especially amiodarone and recently started warfarin. It is significantly more associated with bleeding and higher in-hospital mortality.

Polypharmacy and the geriatric patient

The older adult population is increasing and with it, the risk of polypharmacy. Multiple physicians treating one patient, increasing comorbidities, and an increase in the variety of drugs available contribute to the adverse effects of polypharmacy on the elderly patient. Application of Beers criteria, appropriate therapeutic drug monitoring, and careful, periodic review of the patient's medication list will assist with preventing the sometimes lethal complications of polypharmacy.

Relationship between diet and anticoagulant response to warfarin: a factor analysis

BACKGROUND

Diet composition is one of the factors that may contribute to intraindividual variability in the anticoagulant response to warfarin.

AIM OF THE STUDY

To determine the associations between food pattern and anticoagulant response to warfarin in a group of Brazilian patients with vascular disease.

METHODS

Recent and usual food intakes were assessed in 115 patients receiving warfarin; and corresponding plasma phylloquinone (vitamin K(1)), serum triglyceride concentrations, prothrombin time (PT), and International Normalized Ratio (INR) were determined. A factor analysis was used to examine the association of specific foods and biochemical variables with anticoagulant data.

RESULTS

Mean age was 59 +/- 15 years. Inadequate anticoagulation, defined as values of INR 2 or 3, was found in 48% of the patients. Soybean oil and kidney beans were the primary food sources of phylloquinone intake. Factor analysis yielded four separate factors, explaining 56.4% of the total variance in the data set. The factor analysis revealed that intakes of kidney beans and soybean oil, 24-h recall of phylloquinone intake, PT and INR loaded significantly on factor 1. Triglycerides, PT, INR, plasma phylloquinone, and duration of anticoagulation therapy loaded on factor 3.

CONCLUSIONS

Fluctuations in phylloquinone intake, particularly from kidney beans, and plasma phylloquinone concentrations were associated with variation in measures of anticoagulation (PT and INR) in a Brazilian group of patients with vascular disease.

The effect of hospitalization on oral anticoagulation control: A population-based study

BACKGROUND

For patients taking oral anticoagulants (OAC), the proportion of time spent in the therapeutic range is strongly associated with bleeding and thromboembolic risk. Previous studies examining OAC control may not generalize because the patient population was select or INR capture was incomplete.

OBJECTIVES

Measure OAC control for an entire population of elderly people and determine patient factors associated with OAC control.

PATIENTS

People in Eastern Ontario without valve replacement aged 65 years or greater who were treated with warfarin between 1 September 1999 and 1 September 2000.

DESIGN

Retrospective cohort study using population-based administrative databases. OAC control was measured as the proportion of days in therapeutic range (PDTR), defined as the number days with the INR between 2 and 3 divided by total number of days observation. Linear interpolation was used to determine INR levels between measures. Negative binomial regression was used to identify patient factors independently associated with PDTR. We also determined which factors were associated with proportion of days with a critically low (<1.5) or critically high (>/=5) INR.

RESULTS

7179 people were followed for a total of 3238 years. 15% of people were hospitalized during the study. Overall, PDTR was 59.2% (95% CI 59.1%-59.2%). Independent of all other significant factors, hospitalization was associated with a 15% decrease in the PDTR 15% (rate ratio 0.85, 95% CI 0.83-0.87). Hospitalization was also independently associated with greater proportion of time with a critically low INR (rate ratio 1.68, 95% CI 1.51-1.88) and a critically high INR (1.70, 95% CI 1.38-2.08).

CONCLUSIONS

Elderly people in eastern Ontario taking warfarin were therapeutic 59.2% of the time. Independent of other patient factors, patients who are hospitalized have the greatest risk of poor anticoagulation control. Control for anticoagulated patients who get hospitalized should be reviewed to determine if and how it could be improved.

Effect of Study Setting on Anticoagulation Control

BACKGROUND

For patients receiving therapy with oral anticoagulants (OACs), the proportion of time spent in the therapeutic range (ie, anticoagulation control) is strongly associated with bleeding and thromboembolic risk. The effect of study-level factors, especially study setting, on anticoagulation control is unknown.

OBJECTIVES

Describe anticoagulation control achieved in the published literature. We also used metaregressive techniques to determine which study-level factors significantly influenced anticoagulation control.

STUDIES

All published randomized or cohort studies that measured international normalized ratios (INRs) serially in anticoagulated patients and reported the proportion of time between INRs ranging from 1.8 to 2.0 and 3.0 to 3.5.

RESULTS

We identified 67 studies with 123 patient groups having 50,208 patients followed for a total of 57,154.7 patient-years. A total of 68.3% of groups were from anticoagulation clinics, 7.3% were from clinical trials, and 24.4% were from community practices. Overall, patients were therapeutic 63.6% of time (95% confidence interval [CI], 61.6 to 65.6). In the metaregression model, study setting had the greatest effect on anticoagulation control with studies in community practices having significantly lower control than either anticoagulation clinics or clinical trials (-12.2%; 95% CI, -19.5 to -4.8; p < 0.0001). Self-management was associated with a significant improvement of time spent in the therapeutic range (+7.0%; 95% CI, 0.7 to 13.3; p = 0.03).

CONCLUSIONS

Patients who have received anticoagulation therapy spend a significant proportion of their time with an INR out of the therapeutic range. Patients from community practices showed significantly worse anticoagulation control than those from anticoagulation clinics or clinical trials. This should be considered when interpreting the results of, and generalizing from, studies involving OACs.

Haemorrhagic Complications of Vitamin K Antagonists in the Elderly

In patients >75 years of age, the two main indications for oral anticoagulant therapy with vitamin K antagonists (VKAs) are treatment of venous thromboembolic disease and prevention of systemic embolism in patients with nonvalvular atrial fibrillation. In both indications, a target International Normalized Ratio of 2.5 (range 2.0-3.0) is recommended. Bleeding is the adverse effect feared by physicians that most limits the use of VKAs in older frail patients. In this paper, we discuss (i) the risk of VKA-related bleeding with advancing age; (ii) the severity of bleeding complications and particularly the risk of intracranial haemorrhage in older patients; (iii) the risk factors for bleeding related to patient characteristics; and (iv) the risk factors or determinants for bleeding related to treatment variables (warfarin induction and maintenance administration, instability of anticoagulation, poor compliance and patient's education level, and concomitant use of drugs). Avoiding over-anticoagulation and/or reducing periods of overdosing in the course of oral anticoagulant treatment with tailored monitoring may help to minimise the risk of bleeding in older patients.

Anticoagulant treatment at a specialized outpatient anticoagulant therapy unit, a descriptive study

Background

The indications for continuous oral anticoagulant treatment, the target interval and the procedures for withdrawing treatment have changed in the last 10 years.

Methods

Patients on continuous oral anticoagulant treatment at the Outpatient Anticoagulant Clinic at Umeå University Hospital in 2002 were included in a descriptive study (n = 900). 263 of those had a mechanical heart valve prosthesis. Only patient records for patients with other indications than mechanical heart valve prosthesis were examined. 582 of those records were found. In the 55 remaining patients some clinical information was retrieved from the computerised warfarin dosage database. These latter, more unsure clinical data, are presented separately. Anticoagulant treatment was discontinued if lack of proper indication or presence of too high risk for hemorrhagic complications were found.

Results

The prevalence of continuous oral anticoagulant treatment in the uptake area was 0.65%. The most common target interval was INR 2.1–3.0, but patients with a mechanical heart valve prosthesis were often treated more aggressively, i.e. with a higher INR target interval. Of the patients on continuous treatment, 26.6% of the INR values were outside 2.0–3.0. The most common reasons for oral anticoagulant treatment were atrial fibrillation or mechanical heart valve prosthesis, in contrast to earlier findings in studies of our population in 1987 and 1990. We found 90 patients (10.0%) without proper indication for oral anticoagulant treatment or too high risk, and their treatment was discontinued.

Conclusion

In patients on oral anticoagulant therapy, re-evaluation of indications and risks resulted in a substantial number of treatment withdrawals. There have been major changes in treatment indications during the last decade, possibly due to rapid development of knowledge in the field of thrombosis risk factors. Treatment should be re-considered once a year.

Warfarin Monitoring in Ambulatory Older Individuals Receiving Antimicrobial Therapy

STUDY OBJECTIVE

To determine the frequency of monitoring of international normalized ratio (INR) within 14 days of coprescription of warfarin and antimicrobial therapy and to evaluate differences in INR monitoring among antimicrobials.

DESIGN

Retrospective cohort study.

SETTING

Group model health maintenance organization.

SUBJECTS

Patients aged 65 years or older who were taking warfarin and an antimicrobial agent.

MEASUREMENTS AND MAIN RESULTS

Patients who received dispensings of both warfarin and an antimicrobial agent were identified. We found 2959 coprescribing instances in 1816 patients. The INR values were obtained for 2267 (77%) coprescribing situations within 14 days. Monitoring occurred more frequently (p<0.001) when warfarin was coprescribed with fluoroquinolones (641 [85%] of 755 situations), metronidazole (59 [81%] of 73), tetracyclines (274 [80%] of 341), or macrolides (201 [83%] of 243) than when warfarin was coprescribed with sulfonamides (35 [66%] of 53), penicillins (604 [71%] of 856), or cephalosporins (419 [71%] of 591). Among monitored patients, a higher proportion of monitoring (p<0.001) occurred within 7 days for patients prescribed antifungals (87%), fluoroquinolones (88%), tetracyclines (82%), metronidazole (86%), sulfonamides (86%), or macrolides (85%) than for patients prescribed cephalosporins (68%) or penicillins (75%).

CONCLUSION

Most older patients coprescribed warfarin and an antimicrobial in our organization had INR monitoring within 7 days. This is consistent with appropriate practice to manage a risk of clinically important drug-drug interaction between an antimicrobial agent and warfarin. Prospective identification of patients requiring INR monitoring after coprescription of interacting drugs by using merged administrative pharmacy and laboratory data should be further evaluated as a tool to improve clinical outcomes.

Relative impact of covariates in prescribing warfarin according to CYP2C9 genotype

Patients on warfarin anticoagulant therapy demonstrate wide variation in maintenance dose. Patients possessing variants (*2 and *3) of the cytochrome P450 2C9 gene require reduced maintenance doses compared to those having wild-type alleles (*1). Many other clinical factors have been shown to affect warfarin dose as well. To determine the relative impact of CYP2C9 genotype, age, gender, body surface area, concomitant medication, treatment indication and comorbidity, we conducted a retrospective cohort study in 453 patients managed by the anticoagulation service of a large, horizontally integrated, multispecialty group practice. In this largely Caucasian patient population, the CYP2C9 gene frequencies for *1/*1, *1/*2, *1/*3, *2/*2, *2/*3 and *3/*3 were 65.1%, 19.0%, 12.1%, 1.6%, 1.8% and 0.4%, respectively, approximating Hardy-Weinberg equilibrium. Mean maintenance doses for these genotypes were 36.5, 29.1, 23.5, 28.0, 18.1 and 5.5 mg/week, respectively. In univariate analyses, genotype alone accounted for 19.8% of the variability in maintenance dose. Age, body surface area and male gender accounted for 14.6%, 7.5% and 4.7%, respectively, while cardiac valve replacement as the indication for warfarin accounted for 5.4% of the variability. Collectively, these factors accounted for 33.7% of all dosing variability according to multiple regression. These results will help strengthen the mathematical models that are currently being developed for prospective gene-based warfarin dosing.