Search

Despite a favorable effect of imatinib on glucose metabolism in animal models, human reports are inconsistent. We retrospectively studied the long-term effect of imatinib on fasting plasma glucose (FPG), glycated hemoglobin (HbA1C), LDL-cholesterol (LDL), and triglycerides (TGs) in a large HMO cohort of patients initiating therapy. In patients with diabetes ( n  = 118), significant reductions in HbA1c (0.53%, IQR 0.09, 1.19; p  < .001) and FPG (10.2 mg/dL, IQR -3.5, 32.2; p  < .001), independent of demographics and of glucose-lowering drugs utilization, were observed during the first year of imatinib treatment. Significant reductions in LDL (17.8 mg/dL, IQR -1.3, 34.0; p  < .001) and TG (25.0 mg/dL, IQR -2.3, 58.3; p  < .001), also independent of demographics and of statin utilization, were evident in the entire cohort ( n  = 611) during the first imatinib year. All reductions persisted during the second treatment year. To conclude, imatinib is associated with durable metabolic benefits, which may guide TKI choice in patients with cardiovascular co-morbidities.

Aim: To determine whether oral potassium chloride (KCI) therapy with concomitant anticholinergic exposure among hospitalized patients is associated with an excess risk for upper gastrointestinal bleeding (UGIB)., Methods: A retrospective controlled study among hospitalized patients between January 2007 and April 2019 who were treated with oral KCI. Patients were divided into two groups: with or without concomitant exposure to agents with anticholinergic activity. Outcome was defined as any UGIB., Results: The final sample included 13 728 subjects who received oral KCI treatment, of them 3542 (25.8%) had at least one documented overlap with an anticholinergic agent. Mean age was 67.6 (±17.2) and 6893 (50.2%) were females. Median KCI dose was 2.4 g (interquartile range [IQR] 1.2-5.4, n = 9416) with the majority (90.4%) being treated with the wax-matrix form (Slow-K). Twenty-six (0.2%) patients experienced an UGIB event. Univariate analysis demonstrated a significantly higher rate of UGIB among patients concomitantly treated with oral KCI and anticholinergics (0.3%) compared to those without anticholinergic exposure (0.1%, P = 0.018), with median 7 days (IQR 3-16.8) from first KCI dose to bleeding event. Multivariate analysis demonstrated that concomitant anticholinergic exposure (Odds Ratio 2.48, 95% Confidence Interval 1.11-6.51, P = 0.022) and anticoagulation treatment among patients with hemato-oncologic disease (OR 6.61, 95% CI 1.96-22.25, P = 0.002) were significantly associated with UGIB., Conclusion: Hospitalized patients treated concomitantly with oral KCI and anticholinergic agents have significantly increased risk for UGIB., (© 2020 British Pharmacological Society.)

Background: Uninterrupted drug therapy during acute illness is often associated with pharmacokinetic and pharmacodynamic variations. Among warfarin treated patients, these changes are reflected in the INR. However, in the case of direct oral anticoagulants (DOACs), given that routine laboratory monitoring is not recommended, these changes may result in unforeseen thromboembolic or bleeding events., Objectives: To determine the rate of thromboembolic (TEE) and bleeding events associated with uninterrupted DOAC compared to warfarin treatment during acute illness., Methods: A retrospective cohort study of patients treated with DOACs or warfarin, both at steady state, who were hospitalized for acute illness. Primary outcome was any TEE or major bleeding requiring re-hospitalization within one month from discharge. Secondary outcome was a composite of major bleeding and clinically relevant non-major bleeding (CRNMB) events., Results: A total of 410 patients continued oral anticoagulant treatment during their hospitalization, of whom 191 (46.6%) were on DOACs and 219 (53.4%) on warfarin, with a total of 18 (4.4%) events. Rates of TEE and major bleeding events did not differ between DOACs and warfarin treated patients (0.9% vs. 0.5% and 0.5% vs. 1%, respectively). Similarly, rate of secondary outcome was comparable between DOACs (4.7%) and warfarin (2.7%, p = 0.29). Sub-analyses demonstrated significantly higher rates among rivaroxaban (10.4%) treated patients compared to warfarin (p = 0.03)., Conclusion: Uninterrupted treatment with DOACs during acute illness is not associated with increased risk for re-hospitalizations due to bleeding or thromboembolic events compared to warfarin. Our results suggest a higher bleeding rate among rivaroxaban treated patients at high bleeding risk., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

Background: Prolonged QTc interval observed in daily practice is often deemed to be drug induced and might result in drug discontinuation, with possible therapeutic consequences. However, whether clinically significant prolonged QTc may be due to within-individual variability occurs has yet to be described., Methods: A retrospective cohort study documenting within-individual QTc variability in subjects attending annual routine medical evaluation. At each visit, QT interval was measured and corrected for heart rate using Bazett and three other commonly used formulae. Outcome measures were rates of ΔQTc ≥60 msec, absolute QTc ≥500 msec and QTc ≥25% from baseline., Results: A total of 188 subjects [54 (29%)] females were recruited. Mean age at first ECG was 54 ± 12.8 years with mean time interval of 12.2 ± 1.1 months between measurements. Mean Bazett QTc was higher compared to the other 3 formulae: 412 ± 20 vs. 400 ± 16 msec. Using Bazett formula, 18/188 (9.6%) and 5/188 (2.7%) subjects showed at least one measurement with ΔQTc ≥60 msec and QTc ≥500 msec, respectively. Of the former, 5/18 (27.8%) showed QTc ≥25% prolongation. In multivariate analysis, QTc ≥500 msec was significantly associated with number of measurements (HR: 5.01, 95%CI: 1.21-20.78, p = .026) with no effect of other known confounders. Lower rates were demonstrated with the other three formulae., Conclusion: In clinical practice, significant prolonged QTc may be attributed to within-individual variability, particularly when adjusting the QT interval with Bazett correction. This should be taken into consideration when decisions on changing current drug regimens are to be made., (© 2019 Wiley Periodicals, Inc.)

Competing Interests: Competing interests: None declared.

Background: Clinical decision support systems (CDSS) reduce prescription errors, but their effectiveness is reduced by high alert rates, "alert fatigue", and indiscriminate rejection., Objectives: To compare acceptance rates of alerts generated by the SafeRx ® prescription CDSS among different alert types and departments in a tertiary care hospital, identify factors associated with alert acceptance, and determine whether alert overrides were justified., Methods: In a retrospective study, we compared acceptance rates of all prescription alerts generated in 2013 in 18 departments of Israel's largest tertiary care center. In a prospective study in 2 internal medicine departments, we collected data on factors potentially associated with alert override, and an expert panel evaluated the justification for each overridden alert. We used multivariate analyses to examine the association between patient and physician-related factors and alert acceptance., Results: In the retrospective study, of 390,841 prescriptions, 37.1% triggered at least one alert, 5.3% of which were accepted. Acceptance rates ranged from 7.9% for excessive dose alerts to 4.0% for duplicate drug and major drug-drug interactions alerts (p<0.001). In the prospective study, common reasons for alert overriding included "irrelevance to the specific condition" and "medication previously tolerated by the patient". Weekend shifts (incident rate ratio [IRR]=1.50 [95% CI, 1.01-2.22]) and a specific department (IRR=1.87 [1.23-2.87]) were associated with higher alert acceptance, while night shift (IRR=0.47 [0.26-0.85]) was associated with alert override. Most alert overrides (88.6%) were judged justified., Conclusions: The vast majority of SafeRx ® alerts are overridden, and overriding is justified in most cases. Minimizing the number of alerts is essential to reduce the likelihood of developing "alert fatigue". Our findings may inform a rational, department-specific approach for alert silencing., (Copyright © 2017 Elsevier B.V. All rights reserved.)

Background: In population studies, mild hypomagnesemia, determined by a single measurement, was associated with incident atrial fibrillation, over ~20 years of follow-up. We sought to determine whether mild (≤ 1.7 mg/dL) and moderate (≤ 1.5mg/dL) hypomagnesemia are temporally associated with increased incidence of atrial fibrillation (AF) in the community., Methods: Health Maintenance Organization (HMO) database cohort study including beneficiaries with ≥ 1 serum magnesium measurement between 2004 and 2013. The follow-up period was defined from the first magnesium measurement to first listing in an AF registry (for cases) and December 2013 or date of death or loss to follow-up (for controls). We analyzed the association between serum magnesium quintiles, as well as the above clinically relevant hypomagnesemia thresholds, and incident AF using Cox proportional hazard regression analysis, adjusting for confounders. The association between serum magnesium and AF occurring within 3 months was also examined., Results: Among 162,162 subjects, 2228 (1.4%) developed AF over a median follow-up of 25.3 months. Compared to the middle quintile the lowest magnesium quintile (≤ 1.9 mg/dL) had a significantly higher risk of AF (HR, 1.21; 95% CI: 1.07-1.37). Increased AF risk was also associated with mild (HR, 1.44; 95% CI: 1.20-1.73) and moderate hypomagnesemia (HR, 1.57; 95% CI: 1.14-2.15). No association was found when limiting the follow-up period to 3 months., Conclusions: In our study, hypomagnesemia was associated with incident AF over prolonged but not short-term follow-up periods, suggesting that this association may not be causal., (Copyright © 2015 Elsevier Ireland Ltd. All rights reserved.)

Evidence for the association between hypomagnesemia and proton pump inhibitors (PPIs), highlighted by the 2011 FDA Drug Safety Communication, rests mainly on studies in hospitalized patients. Our objectives were to determine the prevalence of hypomagnesemia and its association with PPIs in the community setting. We performed a retrospective cross-sectional analysis of a large health maintenance organization administrative database, including ambulatory patients with ≥1 serum magnesium concentrations between 2008 and 2011, the lowest referred to as "index magnesium." In cases with any (index magnesium ≤0.7 mmol/L) or severe (≤0.55 mmol/L) hypomagnesemia, we analyzed (vs. controls, >0.7 mmol/L) the association with PPI or H2 -blocker use during the 4-12 months preceding the index magnesium by logistic regression analysis, adjusting for confounders. Among 95,205 subjects, 5,696 (6.0%) had any hypomagnesemia, which was severe in 454 (0.5%), with twofold higher prevalences in those with established risk factors. PPI use during the 4 months preceding the index magnesium was more common in cases of any hypomagnesemia (adjusted OR = 1.66; 95% CI, 1.55-1.78) and severe hypomagnesemia (adjusted OR = 3.79; 2.99-4.82) than in controls without acid suppression. Hypomagnesemia remained significantly associated with PPI use when using H2 -blocker-users as reference (adjusted OR = 1.25 [P = 0.003] and 2.65 [P < 0.001] for any and severe hypomagnesemia, respectively). We conclude that hypomagnesemia is associated with PPI use in ambulatory patients., (© 2014, The American College of Clinical Pharmacology.)

Background: Prescription errors are common in hospitalized patients and result in significant morbidity, mortality and costs. Electronic prescriptions with computerized physician order entry systems (CPOE) and integrated computerized decision support systems (CDSS providing online alerts) reduce prescription errors by approximately 50%. However, the introduction of CDSS is often met by opposition due to the flood of alerts, and most prescribers eventually ignore even crucial alerts ("alert fatigue")., Objectives: To describe the implementation and customization of a commercial CDSS (SafeRx) for electronic prescribing in Internal Medicine departments at a tertiary care center, with the purpose of improving comprehensibility and substantially reducing the number of alerts to minimize alert fatigue., Methods: A multidisciplinary expert committee was authorized by the hospital administration to customize the CDSS according to the needs of six internal medicine departments at Sheba Medical Center. We assessed volume of prescriptions and alert types during the period February-August 2012 using the statistical functions provided by the CDSS., Results: A mean of 339 +/- 13 patients per month per department received 11.2 +/- 0.5 prescriptions per patient, 30.1% of which triggered one or more CDSS alerts, most commonly drug-drug interactions (43.2%) and dosing alerts (38.3%). The review committee silenced or modified 3981 alerts, enhancing comprehensibility, and providing dosing instructions adjusted to the patient's renal function and recommendations for follow-up., Conclusions: The large volume of drug prescriptions in internal medicine departments is associated with a significant rate of potential prescription errors. To ensure its effectiveness and minimize alert fatigue, continuous customization of the CDSS to the specific needs of particular departments is required.

The vitamin K epoxide reductase (VKORC1) is a key enzyme in the vitamin K cycle impacting various biological processes. VKORC1 genetic variability has been extensively studied in the context of warfarin pharmacogenetics revealing different distributions of VKORC1 haplotypes in various populations. We previously identified the VKORC1 Asp36Tyr mutation that was associated with warfarin resistance and with distinctive ethnic distribution. In this study, we performed haplotype analysis using Asp36Tyr and seven other VKORC1 markers in Ashkenazi and Ethiopian-Jewish and non-Jewish individuals. The VKORC1 variability was represented by nine haplotypes (V1-V9) that could be grouped into two distinct clusters (V1-V3 and V4-V9) with intra-cluster difference limited to two nucleotide changes. Phylogeny analysis suggested that these haplotypes could have developed from an ancestral variant, the common V8 haplotype (40 % in all population samples), after ten single mutation events. Asp36Tyr was exclusive to the V5 haplotype of the second cluster. Two haplotypes V5 and V4, distinguished only by Asp36Tyr, were prevalent in both Ethiopian population samples. The V2 haplotype, belonging to the first cluster, was the second most prevalent haplotype in the Ashkenazi population sample (15.8 %) but relatively uncommon in the Ethiopian origin (4.5-4.7 %). We discuss the genetic diversity among studied populations and its potential impact on warfarin-dose management in certain populations of African and European origin.

Background: "Body packers" swallow multiple packets filled with illicit drugs, mainly cocaine, in order to smuggle them across international borders. In recent years, an increasing number of body packers have been hospitalized after their detention by the police upon arrival in Israel., Objectives: To characterize the clinical features and outcomes of body packers hospitalized at the Sheba Medical Center., Methods: We conducted a retrospective case series of body packers hospitalized between January 2010 and October 2012 in our medical center. Electronic medical records and imaging files were reviewed to extract clinical, laboratory and radiological data as well as details on medical treatments., Results: We identified 23 body packers (mean age 38 +/- 10 years), 20 of whom smuggled cocaine from South America. The number of packets transported ranged from 1 to 242 (median 42) and duration of hospitalization from 1 to 14 days (median 2). Two subjects required surgical intervention. All others were treated conservatively by polyethylene glycol-electrolyte lavage solution, laxatives, or watchful waiting. Ten patients underwent a urinary screen for illicit drugs, 7 of whom tested positive for cocaine and 2 for cannabinoids. Abdominal X-rays were performed in all patients at admission, and 14 had follow-up imaging, including abdominal CT scans without contrast media in 8., Conclusions: The main treatment goals for body packers are the rapid excretion of drug packets and early detection of complications, i.e., drug intoxication and bowel obstruction. We suggest the use of a structured treatment approach for the in-hospital management of body packers.

Pharmacogenetic dosing algorithms help predict warfarin maintenance doses, but their predictive performance differs in different populations, possibly due to unsuspected population-specific genetic variants. The objectives of this study were to quantify the effect of the VKORC1 D36Y variant (a marker of warfarin resistance previously described in 4% of Ashkenazi Jews) on warfarin maintenance doses and to examine how this variant affects the performance of the International Warfarin Pharmacogenetic Consortium (IWPC) dose prediction model. In 210 Israeli patients on chronic warfarin therapy recruited at a tertiary care centre, we applied the IWPC model and then added D36Y genotype as covariate to the model (IWPC+D36Y) and compared predicted with actual doses. Median weekly warfarin dose was 35 mg (interquartile range [IQR], 24.5 to 52.5 mg). Among 16 heterozygous D36Y carriers (minor allele frequency = 3.8%), warfarin weekly dose was increased by a median of 43.7 mg (IQR, 40.5 to 47.2 mg) compared to non-carriers after adjustment for all IWPC parameters, a greater than two-fold dose increase. The IWPC model performed suboptimally (coefficient of determination R²=27.0%; mean absolute error (MAE), 14.4 ± 16.2 mg/week). Accounting for D36Y genotype using the IWPC+D36Y model resulted in a significantly better model performance (R²=47.2%, MAE=12.6 ± 12.4 mg/week). In conclusion, even at low frequencies, variants with a strong impact on warfarin dose may greatly decrease the performance of a commonly used dose prediction model. Unexpected discrepancies of the performance of universal prediction models in subpopulations should prompt searching for unsuspected confounders, including rare genetic variants.

Objective: Vitamin D deficiency has been associated in some studies with nonspecific musculoskeletal pain and, more specifically, with statin-induced myalgia, which was ameliorated by high-dose vitamin D supplements. Our objective was to explore the association between vitamin D status and statin-induced myalgia and elevation of serum creatine kinase (CK)., Design: Retrospective cohort study, based on the electronic database of a health maintenance organization., Patients: Six thousand eight hundred and eight patients (71·5% women) to whom statins were dispensed during 2008 and who had ≥1 CK and 25-hydroxy vitamin D (25OHD) levels measured during statin exposure. Of these, 376 patients (5·5%) had switched from a first-line statin to atorvastatin because of muscle pain (n = 220) or other reasons (n = 156). Measurements; In the entire cohort, we compared serum CK levels among serum 25OHD quartiles. In addition, we compared CK and 25OHD levels among patients with myalgia, other switchers and nonswitchers., Results: The median 25OHD level in the entire cohort was 21·8 ng/ml [interquartile range (IQR), 16·3-27·4]. CK levels were marginally lower in patients in the lowest 25OHD quartile [median CK (IQR) in 25OHD quartiles 1-4, 87 (61-130), 90 (65-131), 91 (65-132) and 91 (67-131) IU/ml, respectively; P = 0·007]. 25OHD levels in statin switchers were similar to those in nonswitchers; moreover, there were no differences in 25OHD among switchers with muscle pain and other switchers., Conclusion: Our findings do not support an association between low 25OHD levels and statin-induced myalgia or CK elevation., (© 2011 Blackwell Publishing Ltd.)

Background: In controlled trials, dual therapy with angiotensin-converting enzyme inhibitors (ACE-I) and angiotensin receptor blockers (ARBs) is associated with hyperkalemia and decreased renal function, but there is no information about these adverse effects in clinical practice., Objective: The aim of this study was to assess the incidence of hyperkalemia and decreased renal function during dual therapy (ACE-I plus ARB) in a community-based setting., Methods: In a retrospective cohort database study, we identified patients who received ARBs added to ongoing ACE-I therapy and who had at least 1 measurement of serum creatinine and potassium during each treatment period. We compared rates of hyperkalemia (>5.5 mmol/L) during equal periods of monotherapy and dual therapy and the rate of a significant rise in serum creatinine (≥0.5 mg/dL) between study periods. We assessed the impact of potential confounders on outcomes by logistic regression analysis., Results: Among 425 patients (median follow-up 19 months for each treatment period), hyperkalemia was 2-fold more common during dual therapy than monotherapy (11.1% and 5.6% of patients, respectively) (relative risk = 1.96; 95% CI, 1.22-3.14; P < 0.001). In 77 patients with reduced renal function on monotherapy (serum creatinine ≥1.5 mg/dL), the rate of hyperkalemia was 20.8/100 patient-years, resulting in a number needed to harm of 10.1 patients, compared with 52.6 patients among those with preserved renal function. Mean serum creatinine between treatment periods increased >0.5 mg/dL in 7.5% of patients, more commonly in patients with decreased (18.2%) than with preserved (5.2%) baseline renal function (P < 0.001)., Conclusion: In the community setting, dual therapy was associated with hyperkalemia and a decrease in renal function. The absolute risks were especially high among patients with reduced baseline renal function., (Copyright © 2011 Elsevier HS Journals, Inc. All rights reserved.)

Recent meta-analyses suggest an increased risk of acute myocardial infarction (AMI) in patients with type 2 diabetes mellitus (T2DM) treated with rosiglitazone. These meta-analyses have drawn considerable criticisms. Retrospective observational studies do not consistently support this association. The objective of this study was to compare rates of adverse cardiovascular outcomes in T2DM patients treated with rosiglitazone alone or combined with metformin or metformin alone. This retrospective study, using the health maintenance organization database, included patients who were dispensed rosiglitazone (alone or with metformin) for at least 6 months as follows: rosiglitazone alone (n = 745), rosiglitazone and metformin (n = 2753), and metformin alone (n = 11 938). Adverse cardiovascular outcomes were new diagnosis of AMI, acute coronary syndrome (ACS), coronary revascularization (CRV), congestive heart failure (CHF), and all-cause mortality. Mean on-treatment follow-up was 30 months. After adjustment for covariates found to be significant in univariate analyses, rosiglitazone was associated only with CHF (hazard ratio [HR] = 2.23; 95% confidence interval [CI]: 1.41-1.95) with no increase of risk for AMI (HR = 1.13; 95%CI: 0.60-2.12), ACS (HR = 0.85; 95% CI: 0.57-1.26), coronary revascularization (HR = 1.22; 95% CI:0.82-1.54), or all-cause mortality (HR = 1.15; 95% CI: 0.85-1.56). In this community-based cohort, 30 months of therapy with rosiglitazone treatment was associated with increased risk of CHF but was not associated with increased risk of AMI, ACS, coronary revascularization, or all-cause mortality.

High-dose busulfan (Bu) is frequently used in preparative myeloablative conditioning (MAC) regimens for patients undergoing hematopoietic stem cell transplantation (HSCT). MAC and reduced-intensity conditioning (RIC) protocols for i.v. Bu infusion have been developed to achieve reliable systemic exposure while minimizing toxicity and treatment failure (relapse). The objectives of the present study were to (1) compare the pharmacokinetics (PK) of i.v. Bu in different dosing protocols, (2) compare intrasubject variability of Bu PK over repeated administrations; (3) examine the effect of concomitant administration of fludarabine on Bu PK, and (4) examine the effect of plasma concentrations of glutathione (GSH), the cosubstrate in Bu metabolism, on Bu clearance. We studied Bu PK twice in each of 46 HSCT patients (after the first and then after the middle dose of the treatment cycle) receiving one of 4 dosing protocols, 2 MAC (cumulative dose, 12.8 mg/kg) and 2 RIC (cumulative dose, 6.4 mg/kg), with daily doses administered either as an individual infusion (3.2 mg/kg) or as 4 infusions of 0.8 mg/kg each. Blood samples were obtained for 6-24 hours after dosing for measurement of Bu plasma concentrations. PK parameters were estimated using compartmental analyses. In a subgroup of patients (n = 14), GSH blood concentrations were determined before Bu administration. Dose- and weight-corrected Bu PK parameters (clearance, 0.173 ± 0.051 L/hour · kg; volume of distribution, 0.71 ± 0.17 L/kg; half-life time, 3.0 ± 0.7 hours) did not differ among treatment protocols (all P >.14) and remained stable between the first and mid-cycle doses. Fludarabine did not affect Bu PK. Blood GSH concentrations before Bu dosing were positively correlated with Bu clearance (adjusted R(2) = 0.45; P = .009). Our data indicate that Bu PK parameters are linear, stable, and predictable in different i.v. protocols and are unaffected by coadministration of fludarabine. Differences in whole blood GSH might contribute to variability in Bu clearance., (2011 American Society for Blood and Marrow Transplantation. Published by Elsevier Inc. All rights reserved.)

The considerable variability in the warfarin dose-response relationship between individuals, is explained mainly by genetic variation in its major metabolic (CYP2C9) and target (VKORC1) enzymes. Despite the predominance of pharmacogenetics, environmental factors also affect the pharmacokinetics and pharmacodynamics of warfarin, and are often overlooked. Among these factors, dietary and supplemental vitamin K consumption is a controllable contributor to within-, and between-patient variability of warfarin sensitivity. In this commentary we review the current role of vitamin K in warfarin anticoagulation therapy, with emphasis on the following: 1 The effect of dietary and supplemental vitamin K on warfarin anticoagulation, beyond the impact of genetic variability in CYP2C9 and VKORC1. We deal separately with the effects of vitamin K on warfarin dose requirements during the induction of therapy, as opposed to its effect on stability of anticoagulation control during maintenance therapy. 2 The role of vitamin K supplementation in warfarin treated patients with vitamin K deficiency as well as in patients with unstable warfarin anticoagulation, and 3 The role of therapeutic vitamin K in cases of warfarin over-anticoagulation.

Since the first report on warfarin pharmacogenetics in 1999, genetic variants have emerged as an important predictor of warfarin maintenance doses before therapy is initiated, raising expectations of greatly improved clinical outcomes. However, much of the information on warfarin sensitivity conveyed by genetic variants is captured by early international normalized ratio values traditionally used to guide dose titration. Thus, inclusion of early international normalized ratios in prediction models reduces the contribution of genetics. Moreover, in large population cohorts, genetics explained only 20-30% of variance in warfarin doses. Finally, even pharmacogenetic prediction models did not predict doses reliably in the majority of at-risk patients with warfarin requirements at the low or high end of the dose range. Currently, the clinical utility and cost-effectiveness of pharmacogenetic-based dosing are being assessed in large prospective trials in various settings. In the interim, enthusiasm for warfarin pharmacogenetics should not supersede strict adherence to traditional measures used to optimize coumarin anticoagulation.

Background: Infections with blood-borne viruses are a major health problem among illicit drug users. There is little information about infection rates and risk factors for hepatitis virus B, C or the human immunodeficiency virus in drug users in Israel., Objectives: To determine the prevalence of HCV, HBV and HIV infections in a large cohort of drug users in Israel; to compare rates of HCV, HBV and HIV between injecting versus non-injecting drug users and between different countries of origin; and to identify risk factors for HCV among illicit drug users., Methods: We conducted a cross-sectional study using an interviewer-administered questionnaire and serological screening for HCV, HBV and HIV in 1443 consecutive drug users diagnosed at the Israeli National Center for Diagnosis of Drug Addicts between January 2003 and December 2005., Results: Fourteen (0.9%), 51 (3.5%) and 515 (35.7%) subjects tested positive for HIV, HBV and HCV, respectively. All three infections (HIV, HBV and HCV) were significantly more common among injecting drug users and immigrants from the former Soviet Union and other East European countries compared to native Israelis. Multivariate analysis showed that HCV infection was associated with age (> 40 years) (OR=2.06, 95% CI 1.40-3.03), immigration from East European countries and the former Soviet Union (OR=4.54, 95% CI 3.28-6.28), and injecting drug use (OR=16.44, 95% CI 10.79-25.05)., Conclusions: HIV, HBV and HCV prevalence among drug users in Israel is significantly lower than in North America and West Europe. Risk factors for HCV infection in this population include injecting drug use, older age, and immigration from the former Soviet Union.

Background: To compare the effectiveness of brand rosiglitazone maleate (BRM) versus generic rosiglitazone HCl (GRH) in patients with type 2 diabetes mellitus, using computerized records of a healthcare organization. Retrospective, longitudinal database analysis., Material/methods: Comparison of HbA1C reduction in patients starting treatment with either BRM (n=740) or GRH (n=306) in the years 2004-2005., Results: BRM users were older (63.5+/-11 vs. 61.7+/-10 years p<0.001) and presented more cardiovascular disorders (38% vs. 25%, p<0.001) with no differences in gender distribution, rates of hypertension or use of concomitant oral hypoglycemic drugs. Use of concomitant insulin was more frequent (17.7% vs. 6.2%, p<0.0001), rates of dispensed rosiglitazone doses >4 mg/d (65.3% vs. 48.5%, p<0.001) and treatment duration was longer (9.3+/-6.2 vs. 5.2+/-2.2 months, p<0.001) with the generic formulation. Baseline HbA1C levels were higher (9.0+/-1.5 vs. 8.6+/-1.2%, p<0.001) and the absolute decrease in HbA1C levels was greater in the GRH group (-1.2+/-1.6% vs. -0.5+/-1.7%, p<0.001). On multiple regression analysis, the decrease in HbA1C (dependent variable) was associated mainly with initial HbA1C level (partial r2=0.30). Rosiglitazone formulation (partial r2=0.02), age, treatment duration and concomitant insulin (partial r2=0.006) were all significant but minor predictors, with no effect of rosiglitazone daily dose. Mean regression-predicted decreases in HbA1C (with 95% CL) were not significantly different between the two rosiglitazone formulations: -1.6% (-4.3% to +1.1%) for GRH and -1.1% (-3.8% to +1.6%) for BRM., Conclusions: In this retrospective database analysis, we found no evidence of different effectiveness of generic vs. brand rosiglitazone in lowering HbA1C levels.

Exercise capacity and training response are limited in chronic obstructive pulmonary disease (COPD), but the extent to which this is related to altered skeletal muscle function is not fully understood. To test the hypothesis that muscle gene expression is altered in COPD, we performed needle biopsies from the vastus lateralis of six COPD patients and five sedentary age-matched healthy men, before and after 3 mo of exercise training. RNA was hybridized to Affymetrix U133A Genechip arrays. In addition, peak O(2) uptake and other functional parameters (e.g., 6-min walk) were measured before and after training. The 6-min walk test increased significantly following training in both groups (53.6 +/- 18.6 m in controls, P = 0.045; 37.1 +/- 6.7 m in COPD, P = 0.002), but peak O(2) uptake increased only in controls (19.4 +/- 4.5%, P = 0.011). Training significantly altered muscle gene expression in both groups, but the number of affected genes was lower in the COPD patients (231) compared with controls (573). Genes related to energy pathways had higher expression in trained controls. In contrast, oxidative stress, ubiquitin proteasome, and COX gene pathways had higher expression in trained COPD patients, and some genes (e.g., COX11, COX15, and MAPK-9) were upregulated by training only in COPD patients. We conclude that both COPD and control subjects demonstrated functional responses to training but with somewhat different patterns in muscle gene expression. The pathways that are uniquely induced by exercise in COPD (e.g., ubiquitin proteasome and COX) might indicate a greater degree of tissue stress (perhaps by altered O(2) and CO(2) dynamics) than in controls.

CYP2C9 and VKORC1 genetic variants are associated with low and intermediate warfarin dose requirements, but markers of high doses are less well characterized. We analyzed the VKORC1 coding sequence and known CYP2C9 and VKORC1 polymorphisms in 15 selected warfarin-resistant (dose, 80 to 185 mg/wk) and 8 warfarin-sensitive patients (7 to 13 mg/wk) and 99 unselected controls (8 to 105 mg/wk). We identified a coding VKORC1 Asp36Tyr polymorphism in 7 of 15 resistant compared with 0 of 8 sensitive patients (P = .026) Carriers of Asp36Tyr in the control group (8 of 99) required significantly higher warfarin doses of 80.9 +/- 10.1 mg/wk compared with 42.7 +/- 7.5 mg/wk in noncarriers (F = 9.79, P = .002). Asp36Tyr was significantly associated with doses of more than 70 mg/wk (odds ratio, 13.0; 95% confidence limit, 1.3 to 124.2), while doses of 20 to 70 mg/wk were associated with Asp36Tyr (partial r(2) = .11; P = .004), CYP2C9*2 and *3 (r(2) = .08; P = .01), and VKORC1*2 and *3 markers (r(2) = .05; P = .05). All Asp36Tyr carriers also had VKORC1*1 tag-single nucleotide polymorphisms (tag-SNPs) indicating a new haplotype. Asp36Tyr was common in Jewish ethnic groups of Ethiopian (15%) and Ashkenazi (4%) origin. We suggest that Asp36Tyr is a new marker of the high end of the warfarin dosing range.

Background: Adverse reactions related to the upper gastrointestinal tract (UGIT) that are associated with generic alendronate formulations may differ from those associated with the brand drug., Objective: To test the hypothesis that adverse UGIT effects of alendronate formulations may differ between generic and brand products., Methods: We conducted a database health resource utilization analysis of UGIT outcomes in patients who started treatment with generic or brand alendronate formulations during 2001-2005. We included 6962 patients who were treated continuously for 3 months with 1 of 4 alendronate formulations: brand 10 mg/day (Merck, Sharpe & Dohme, n = 1418), generic A 10 mg/day (Teva, Israel, n = 650), generic B 10 mg/day (Unipharm, Israel, n = 628), and brand 70 mg/wk (n = 4266). In these patients, who had neither filled a prescription for alendronate nor had any gastrointestinal problems in the year preceding the study, we compared incidence rates of new use of gastric medications (H2-blockers, proton-pump inhibitors, or antacids), gastroenterology visits, endoscopies, and hospital admissions., Results: Incident rate ratios (IRR) for treatment discontinuation were higher with both daily generic products (IRR 1.3; 95% CI 1.04 to 1.63). Adherence (medication possession ratio [MPR] >80%) was better with brand 10 mg/day (IRR 1.19; 95% CI 1.11 to 1.27). All comparisons were adjusted for use of concurrent corticosteroids, nonsteroidal antiinflammatory drugs, and potassium supplements. Hospitalization rates (2.7-3.2%) were similar in all groups. New use of gastric medications (3.4-4.9%) was lower with brand 10 mg/day (IRR 0.71; 95% CI 0.53 to 0.95). Rates of UGIT endoscopy (n = 49) in patients receiving 10 mg were 0.6% (brand), 1.1% (generic A), and 1.6% (generic B), with generic B higher (IRR 2.88; 95% CI 1.14 to 7.29) in the entire cohort, but not among new users (n = 273) of gastric drugs (IRR 2.46; 95% CI 0.55 to 11.05). Endoscopic findings were normal in 22 patients, hiatal hernia with no mucosal lesion was present in 10 patients, and there was mild-to-moderate esophagitis or gastritis in 17 patients; there were no significant differences among the formulations., Conclusions: We found insufficient evidence to indicate major differences in UGIT adverse effects related to use of daily generic, as compared with brand, alendronates.

Objectives: To describe the development of inclusion criteria for identifying diabetic patients using administrative, laboratory and pharmacy data on a large central electronic database., Design: A descriptive study in which entry criteria were developed, validated then changed in an iterative fashion and revalidated. The final register was compared with a traditionally built diabetes register., Results: The four criterion chosen were: 1) HbAlc> or = 7.25%; 2) Glucose> or = 200mg/dl (for individuals who are included in the register on this criterion alone, supporting data for the diagnosis of diabetes is required at six months. If none are found, the patient is deleted from the register); 3) Purchase of diabetic medication twice in the last two months; 4) A diagnosis of diabetes (ICD9 code) in the chart and HbA1c6.5% or Glucose > 125mg/dl., Conclusion: Adoption of criteria for identification of diabetic patients using data sets on central computers can provide the registers necessary for diabetes care.

The rapidly rising health care expenditures, attributed mainly to the high cost of prescription drugs, have led governments around the world to look to generics as a means of containing costs in the pharmaceutical market. Generic drugs provide a less expensive alternative to brand name drugs due to the elimination of the need to perform lengthy and costly clinical trials, as required for innovative drugs. Essentially, generic substitution of drugs may be performed only after showing unequivocally that the generic formulation is identical in its active ingredients, strength, and route of administration as its innovative counterpart, and that they are bioequivalent to each other. Although the two are in essence the same, generic substitution is occasionally a controversial matter.

Background: It has been demonstrated by meta analysis that if a regular review of patients is guaranteed, the standard of primary care can be as good or better than hospital outpatient care, however, empirical data suggests that compliance with diabetes clinical practice recommendations is inadequate in primary care. This study describes the reorganization of diabetes care using disease management principles in a Preferred Provider Organization (PPO) operating on a country-wide basis in which each diabetes clinic became responsible for the overall care of all patients with diabetes., Methods: This descriptive pre and post change study was undertaken in a large public-funded PPO insuring over one and half million individuals. The study was possible due the use of a centralized electronic disease registry which enabled the collection of all patient data. Several markers, such as HbA1C and LDC-cholesterol levels, were used to assess the quality of care for the diabetic patients., Results: Mean HbA1C results of the cohort showed a continuous reduction from 8.1% (S.D. = 1.55) in 1999 to 7.68% (S.D. = 1.47) in 2002 and to 7.79 (S.D. = 1.54) in 2004. Improved results were also recorded for LDL-C 126.37 (S.D. = 35.16) in 1999 to 114.74 (S.D. = 34.49) in 2002, and to 113.39 (S.D. = 33.8) in 2004. The number of diabetic patients seen by the diabetologist increased by 62% over this period, despite an increase in diabetologist work hours of only 23%., Conclusion: The reorganization of health delivery for diabetic patients within a country-wide PPO, based on the principles of disease management and supported by medical informatics improves quality of care.

We examined the influence of combined genotypes on interindividual variability in warfarin dose-response. In 100 anticoagulated patients we quantified the effects of polymorphisms in: CYP2C9, VKORC1, calumenin (CALU), gamma-glutamyl carboxylase (GGCX) and microsomal epoxide hydrolase (EPHX1) on warfarin dose requirements. The G(1542)C VKORC1 polymorphism was associated with decreased warfarin doses in the hetero- and homozygous mutant patients (21% and 50% lower, respectively; p < 0.0001). Warfarin daily dose was predominantly determined by VKORC1 and CYP2C9 genotypes (partial r(2) = 0.21; 0.20, respectively). Together with age and body weight, these two genotypes explained 63% of the dose variance. A single patient, homozygous for G(11)A CALU mutant allele, required an exceptionally high warfarin dose (20 mg/day) and the prevalence of heterozygous (11)A allele carriers in the upper 10(th) dose percentile was significantly higher (0.27 vs. 0.18, p < 0.02). Combined genotype analysis revealed that CYP2C9 andVKORC1 wild type and CALU mutant patients required the highest warfarin doses (7.8 +/- 1.5mg/day; n = 9) as compared to the CYP2C9 and VKORC1 mutant and CALU wild type genotypes (2.8 +/- 0.3 mg/day; n = 18; p < 0.01). The odds ratio for doses <3mg/day was 5.9 (1.9-18.4) for this genotype. Compound genetic profiles comprising VKORC1, CALU and CYP2C9 improve categorization of individual warfarin dose requirements in more than 25% of patients at steady-state anticoagulation.

Background: Warfarin dose response is partially explained by the polymorphisms in the cytochrome P450 (CYP) 2C9 gene, affecting S -warfarin clearance, as well as by age and body weight. We examined the influence on warfarin dose requirements of candidate genes encoding microsomal epoxide hydrolase (mEH), as well as glutathione S -transferase A1 (GSTA1) components of vitamin K epoxide reductase and the gamma-glutamylcarboxylase (GGCX) gene., Methods: We studied the effects of CYP2C9, mEH, GSTA1, and GGCX genotypes on warfarin maintenance doses, accounting for age, weight, vitamin K plasma concentrations and concurrent medications, in 100 patients undergoing therapeutic anticoagulation., Results: Allele frequencies were 76.5%, 12.5%, and 11% for CYP2C9*1 , *2 , and *3 , respectively; 75% and 25% for mEH T 612 C; 75.8% and 24.2% for mEH A 691 G; 73.5% and 26.5% for GSTA1 T 631 G; and 70.5% and 29.5% for GGCX G 8762 A. Warfarin doses differed among the CYP2C9 ( 2C9*1 , 2C9*2 , and 2C9*3 ) genotype groups: 6.3 +/- 1.9 mg/d, 5.3 +/- 1.8 mg/d, and 3.8 +/- 1.7 mg/d, respectively (F = 4.83, P < .01). There were no differences in any of the other genotype groups. Among the 62 wild-type CYP2C9 patients, variant mEH T 612 C homozygotes required higher doses than heterozygotes and wild-type patients (7.5 +/- 2.9 mg/d, 6.5 +/- 4.2 mg/d, and 6.0 +/- 2.6 mg/d, respectively [F = 3.57, P = .03]). The odds ratio for requiring greater than 7 mg/d in variant mEH T 612 C patients versus wild-type patients was 3.14 (95% confidence interval, 1.47-6.67), accounting for CYP2C9., Conclusions: Variant mEH T 612 C genotypes are associated with warfarin doses of greater than 50 mg/wk beyond the effect of CYP2C9.

Background: Oral anticoagulation with warfarin can lead to life-threatening events as a result of either over-anticoagulation or undertreatment. One of the main contributors to an undesirable warfarin effect is the need to adjust its daily dose for a specific patient. The dose is adjusted empirically based on the experience of the clinician, a method that is often imprecise. There is currently no other well-accepted method for predicting the maintenance dose of warfarin., Objective: To describe the application of an artificial neural network to the problem of warfarin maintenance dose prediction., Methods: We designed a neural network that predicts the maintenance dose of warfarin. Data on 148 patients attending a large anticoagulant clinic were collected by file review. Using correlational analysis of the patients' data we selected the best input variables. The network was trained by using the back-propagation algorithm on a subset of our data and the results were validated against the rest of the data. We used a multivariate linear regression to create a comparable model., Results: The neural network generated reasonable predictions of the maintenance dose (r = 0.823). The results of the linear regression model were similar (r = 0.800)., Conclusion: Neural networks can be applied successfully for warfarin maintenance dose prediction. The results are promising, but further investigation is needed.

Most multivitamin supplements contain far less vitamin K(1) than thought to affect warfarin anticoagulation. Having described 3 patients with multivitamin-warfarin interactions, we hypothesized that vitamin K(1)-depleted patients are sensitive to even small increments. Therefore, we compared the effect of a vitamin K(1)-containing multivitamin on warfarin anticoagulation between patients with low versus normal vitamin K(1) status. We screened 102 warfarin-treated patients and recruited nine with "low" (< 1.5 mcg/L, 10(th) percentile) (group 1) and 7 with "normal" (>4.5 mcg/L, median) (group 2) total vitamin K(1) plasma levels (vitamin K(1) + vitamin K(1) 2,3-epoxide). Patients received one multivitamin tablet containing 25 mcg of vitamin K(1) daily, for 4 weeks (period 1). A predefined algorithm was used to adjust warfarin doses if the INR was outside the therapeutic range. Patients requiring warfarin increments were then switched to 4 weeks of a vitamin K(1)-free multivitamin supplement (period 2). During period 1, subtherapeutic INRs occurred in 9/9 and 1/7 patients in group 1 and 2, respectively (p <0.001). In group 1, INR decreased by a median of 0.51 (p <0.01), and warfarin dose had to be raised by 5.3% (p <0.01), whereas INR and warfarin dose did not change significantly in group 2. During period 2 (7 patients), there were trends towards decreased total vitamin K(1) and rising INRs associated with significantly lower warfarin doses. We conclude that vitamin K(1)-containing multivitamins reduce INR in patients with low vitamin K(1) status. Our study suggests that vitamin K-depleted patients are sensitive to even small changes in vitamin K(1) intake.

Many patients with cardiac arrhythmias require concomitant therapy with warfarin and amiodarone. Beyond the predictable pharmacokinetic drug-drug interaction requiring a significant warfarin dose reduction, the iodine-rich amiodarone affects the thyroid gland, causing overt hypothyroidism or thyrotoxicosis in 14%-18% of cases. In turn, thyroid disorders may affect warfarin sensitivity, with hypothyroidism and thyrotoxicosis resulting in increased or decreased warfarin requirements, respectively. We describe 3 patients on concomitant amiodarone and warfarin who developed amiodarone-induced thyrotoxicosis heralded by a significant decrease in warfarin requirements. We review the literature on the mechanisms of the complex drug-drug and drug-disease interactions within the thyroid gland, warfarin, and amiodarone triad. Given that significant thyroid disorders may be only mildly symptomatic and thus may escape clinical detection, we suggest that thyroid function should be tested in any patient with otherwise unexplained changes in warfarin dose requirements, particularly if concomitantly treated with amiodarone.

Background: Treatment of patients with excessive anticoagulation is routinely done by intravenous phytonadione (vitamin K1). Oral administration of phytonadione has been shown to be an effective alternative to the intravenous route, but these methods have never been compared directly. Our objective was to compare efficacy and safety of intravenous vs oral phytonadione treatment in patients with excessive anticoagulation without bleeding., Methods: The study was a prospective randomized controlled trial of consecutive patients presenting with excessive anticoagulation without major bleeding. Patients with a baseline international normalized ratio (INR) of 6 to 10 (n = 44, 47 episodes) received either intravenous or oral phytonadione (0.5 mg or 2.5 mg, respectively), and patients with an INR greater than 10 (n = 17, 19 episodes) received 1 mg or 5 mg, respectively. Efficacy and safety end points were sequential INR changes and the proportion of patients achieving therapeutic range (INR, 2-4), overcorrection (INR<2.0), or undercorrection (INR>4.0) INR values., Results: Sixty-six episodes of excessive anticoagulation were studied. In patients with baseline INR 6-10 the response to intravenous phytonadione was more rapid than in the oral group, and the proportion of patients reaching therapeutic range INR at 6 hours (11/24 vs 0/23) and at 12 hours (16/24 vs 8/23) was significantly higher. However, mean +/- SD INR values were similar for both groups at 24 hours (2.9 +/- 0.8 vs 2.6 +/- 0.8). Patients in the intravenous group tended to be more often (7/24 vs 2/23) overcorrected (INR<2). In patients with baseline INR values greater than 10 efficacy and safety were comparable for both routes of administration., Conclusion: Oral administration of phytonadione had similar efficacy and safety as intravenously administered phytonadione and may be suitable for treatment of patients with excessive anticoagulation.

Objective: To report an interaction of a multivitamin preparation containing small amounts of vitamin K(1) (25 microg) with warfarin in a case series and to assess the prevalence of vitamin K(1) deficiency in ambulatory anticoagulated patients., Case Summaries: We describe 3 patients whose anticoagulation was stabilized with warfarin in whom initiation or cessation of a self-prescribed multivitamin supplement delivering 25 microg of vitamin K(1) daily was associated with an otherwise unexplained significant fall or rise in international normalized ratio (INR), respectively, with major thrombosis or hemorrhage in 2. This interaction was rated probable on the Naranjo probability scale. Suspecting vitamin K(1) deficiency as an explanation for this oversensitivity, we assessed the prevalence of vitamin K(1) deficiency in our clinic by determining plasma vitamin K(1) levels in 179 stable consecutive patients, finding very low levels (<0.1 ng/mL) in 22 of 179 (12%)., Discussion: Vitamin K(1) supplements of 25 microg daily are far below the dose thought to affect anticoagulant control. We hypothesize that, in our patients, unsuspected vitamin K(1) deficiency caused an oversensitivity to small vitamin K(1) supplements. In patients with low vitamin K(1) status, even such low doses represent a significant increment in daily intake, thus lowering the sensitivity to warfarin. Our analysis suggests that low vitamin K(1) status exists in a small, but important, minority of ambulatory patients undergoing anticoagulation., Conclusions: Clinicians should instruct anticoagulated patients to report the use of multivitamin supplements and inquire about it in cases of unexplained INR changes.

Objective: Our objective was to examine possible changes in the effectiveness of warfarin after a nationwide generic substitution of formulations in 1998., Methods: In the computerized records of a health maintenance organization database, we identified 975 patients who took warfarin continuously over two 6-month periods, before (period 1) and after (period 2) the generic switch. In this sample we performed a retrospective, between-period paired comparison of warfarin doses dispensed and international normalized ratio (INR) levels maintained, as well as of the apparent warfarin sensitivity index (calculated as INR/Warfarin dose [in milligrams per day])., Results: Overall, for period 2, doses were 26.5% higher and INR 4.2% lower, with a 14.7% reduction in warfarin sensitivity index (P <.001). The findings were strongest in the 61 of 975 patients (6.3%) dispensed the lowest maintenance doses (<1.0 mg/d), with minimal change at greater than 3 mg/d. In 94 other patients (9.6%) in whom doses were unchanged, INR (median with 5th and 95th percentiles) dropped to subtherapeutic levels, from 2.2 (1.8, 3.0) to 1.7 (1.3, 1.8) (P <.001). There were no adverse events, expressed as no change in hospital admissions. Apparent warfarin sensitivity was reduced in period 2 by 15% to 20% (P <.001) across all period 1 INR levels., Conclusion: Because a general unidirectional change in INR response per unit warfarin dose cannot be explained by biologic mechanisms or confounding, we conclude that slightly reduced bioavailability (within the acceptable bioequivalence range) of the new formulation led to overestimated period 2 doses and reduced apparent warfarin sensitivity in all patient subgroups (by period 1 dose or INR), which was most prominent in those individuals with the lowest maintenance dose requirements.

Portable prothrombin time (PT) monitors facilitate the control of warfarin therapy. Few studies have compared the influence of using different monitors on dosage decisions. We determined the comparability of data generated by two portable PT monitors, Coaguchek S, (Roche Diagnostics Boehringer-Mannheim) and Hemochron Jr (International Technidyne Corporation Ltd.), with that of a reference laboratory. Simultaneous International Normalized Ratio (INR) measurements (portable monitor and laboratory) were performed in 193 consecutive patients receiving warfarin for at least 3 months. Agreement of measurements was assessed by both regression analysis and influence on dosage decisions in accordance with pre-defined criteria. The Coaguchek S versus laboratory INR regression line (n = 111; r2 = 0.88; P < 0.001) was close to the line of identity, while that of the Hemochron Jr (n = 82; r2 = 0.61; P < 0.001) was not. The overall proportion of dual INR measurements that fulfilled the clinical criteria of agreement was 90% for the Coaguchek S compared with 62% for the Hemochron Jr (P < 0.0001). For laboratory INRs 2.0-2.5, 2.6-4.0 and > 4.0, the proportions of portable measurements that satisfied the clinical criteria for the Coaguchek S versus the Hemochron Jr were 96 versus 63% (P < 0.001), 81 versus 45% (P < 0.04), and 67 versus 17% (P < 0.85), respectively. Warfarin dosing based solely on the portable devices would have resulted in unjustified dose increments in 22% of the patients with the Hemochron Jr device compared with 8% with the Coaguchek S monitor (chi2 = 4.43; P = 0.035). The Coaguchek S monitor provides measurements for INR values within the therapeutic range that agree well with the standard laboratory. The Hemochron Jr measurements result in different dosage adjustments even within the therapeutic range, but especially for INR values > 4.0. For both monitors, agreement of INR measurements with the standard decreases with increasing INR values.

Administration of vitamin K is the common mode of treatment in excessively anticoagulated patients. However, patient's response to vitamin K varies, depending on the vitamin K dose and the route of administration. Another potential source of variation is the pre-treatment INR which has not been accounted for in most previous studies. In the present study the effect of baseline INR on the response to a single dose of intravenous vitamin K (0.5 mg) was studied in 95 episodes of excessively anticoagulated patients (n = 76). In 67 episodes of moderately excessive baseline INR (6-10) mean INR declined from 8.0 +/- 1.2 to 2.6 +/- 0.9 at 24 hours, 59/67 (88%) responding within the first 12 hours and not requiring a second dose. In contrast, in 28 episodes with highly excessive baseline INR (> 10) response was slower; mean INR declining from 13.6 +/- 2.7 to 4.0 +/- 2.1 at 24 hours. In 14/28 of these episodes, patients failed to respond to vitamin K in the first 12 hours and required a second vitamin K dose. We conclude that INR at presentation affects the response to vitamin K and that this INR value should be considered in determining appropriate vitamin K doses.