Fibrate/Statin initiation in warfarin users and gastrointestinal bleeding risk

Peroxisome Proliferator-Activated Receptor α in Lipoprotein Metabolism and Atherosclerotic Cardiovascular Disease

Peroxisome proliferator-activated receptors (PPARs) are a group of ligand-binding transcription factors with pivotal action in regulating pleiotropic signaling pathways of energetic metabolism, immune responses and cell proliferation and differentiation. A significant body of evidence indicates that the PPARα receptor is an important modulator of plasma lipid and lipoprotein metabolism, with pluripotent effects influencing the lipid and apolipoprotein cargo of both atherogenic and antiatherogenic lipoproteins and their functionality. Clinical evidence supports an important role of PPARα agonists (fibric acid derivatives) in the treatment of hypertriglyceridemia and/or low high-density lipoprotein (HDL) cholesterol levels, although the effects of clinical trials are contradictory and point to a reduction in the risk of nonfatal and fatal myocardial infarction events. In this manuscript, we provide an up-to-date critical review of the existing relevant literature.

A Case of Unexplained Warfarin Resistance: A Case Report and Literature Review

Adjusting the exact warfarin dose has always been challenging since it has a narrow therapeutic window. Numerous factors, including poor drug compliance, drug-drug interactions, and malabsorption syndromes, affect the warfarin plasma concentration, leading to oversensitivity or resistance to warfarin. Patients who need more than 15 mg/d of warfarin for maintained anticoagulant effects are considered warfarin resistant. We describe a 62-year-old man referred to our center with bruising on his feet in June 2021. The patient had a history of valve replacement (mechanical prosthetic valves in 2013), hypothyroidism, and atrial fibrillation. He presented with warfarin resistance (first noticed in 2013) and did not reach the desired warfarin therapeutic effect despite receiving 60 mg of warfarin daily. Upon admission, the patient was on warfarin (100 mg/d) with an international normalized ratio (INR) of 1.5. He underwent laboratory and molecular genetic tests, which showed no mutation in the CYP2C9 and VKORC1, the genes associated with warfarin resistance. A stepwise diagnosis is required to identify the underlying cause. Assessing the patient's compliance, drug history, dietary habits, malabsorption diseases, and genetics may be necessary. We evaluated these possible reasons for resistance and found no correlation. The patient's warfarin intake was monitored closely to reach the INR therapeutic target of 3-3.5. He decided to leave the hospital with personal consent. He was discharged with a cardiologist referral and 24 warfarin tablets daily (120 mg/d) with an INR of 1.8. The patient was followed up 6 months and 2 years after discharge and was on the same daily dose of warfarin as at discharge, with no complications.

Tissue Engineering and Targeted Drug Delivery in Cardiovascular Disease: The Role of Polymer Nanocarrier for Statin Therapy

Atherosclerosis-related coronary artery disease (CAD) is the leading cause of mortality and morbidity worldwide. This requires effective primary and secondary prevention in reducing the complications related to CAD; the regression or stabilization of the pathology remains the mainstay of treatment. Statins have proved to be the most effective treatment in reducing adverse effects, but there are limitations related to the administration and achievement of effective doses as well as side effects due to the lack of target-related molecular specificity. The implemented technological steps are polymers and nanoparticles for the administration of statins, as it has been seen how the conjugation of drug delivery systems (DDSs) with statins increases bioavailability by circumventing the hepatic–renal filter and increases the related target specificity, enhancing their action and decreasing side effects. Reduction of endothelial dysfunction, reduced intimal hyperplasia, reduced ischemia–reperfusion injury, cardiac regeneration, positive remodeling in the extracellular matrix, reduced neointimal growth, and increased reendothelialization are all drug-related effects of statins enhanced by binding with DDSs. Recent preclinical studies demonstrate how the effect of statins stimulates the differentiation of endogenous cardiac stem cells. Poly-lactic-co-glycolic acid (PLGA) seems to be the most promising DDS as it succeeds more than the others in enhancing the effect of the bound drug. This review intends to summarize the current evidence on polymers and nanoparticles for statin delivery in the field of cardiovascular disease, trying to shed light on this topic and identify new avenues for future studies.

Risk of Gastrointestinal Bleeding on Treatment With Statin Alone or With Concomitant Administration of Warfarin: A Systematic Review and Meta-analysis of 5.3 Million Participants

OBJECTIVE

This study aimed to comprehensively evaluate the risk of gastrointestinal bleeding (GIB) with statin monotherapy or with concomitant warfarin use.

DATA SOURCES

PubMed, Web of Science, and EMBASE (via Scopus) were searched for observational studies that reported the risk of GIB in adults on statin therapy or with concomitant warfarin use until August 28, 2021.

STUDY SELECTION AND DATA EXTRACTION

Observational studies evaluating the risk of GIB in adults (age >18 years) on statin medication or concomitant use with warfarin were included.

DATA SYNTHESIS

In all, 14 studies with a total of 5 235 123 participants, reporting 48 677 GIB events (43 734 from statin users and 4943 from users of statin combined with warfarin), were included in the analyses. The pooled analysis revealed no difference in the risk of GIB with statin monotherapy (relative risk [RR]: 0.65; 95% CI: 0.42-1.02) or concomitant statin + warfarin use (RR: 0.97; 95% CI: 0.91-1.02). Prior use of statin was not associated with GIB risk (RR: 0.88; 95% CI: 0.63-1.22), whereas a shorter duration of statin use (<5 years) was associated with a lower risk of GIB (RR: 0.42; 95% CI: 0.18-0.97).

RELEVANCE TO PATIENT CARE AND CLINICAL PRACTICE

This analysis provides strong evidence on the association between statin use (with/without warfarin) and risk of GIB.

CONCLUSION

Statin alone or combined with warfarin was not significantly associated with either an increased or decreased risk of GIB. The GIB risk was significantly lower when statins were used for a short duration (<5 years). The putative relationship between statins and GIB in warfarin users warrant further investigation.

Edoxaban and the Issue of Drug-Drug Interactions: From Pharmacology to Clinical Practice

Edoxaban, a direct factor Xa inhibitor, is the latest of the non-vitamin K antagonist oral anticoagulants (NOACs). Despite being marketed later than other NOACs, its use is now spreading in current clinical practice, being indicated for both thromboprophylaxis in patients with non-valvular atrial fibrillation (NVAF) and for the treatment and prevention of venous thromboembolism (VTE). In patients with multiple conditions, the contemporary administration of several drugs can cause relevant drug-drug interactions (DDIs), which can affect drugs' pharmacokinetics and pharmacodynamics. Usually, all the NOACs are considered to have significantly fewer DDIs than vitamin K antagonists; notwithstanding, this is actually not true, all of them are affected by DDIs with drugs that can influence the activity (induction or inhibition) of P-glycoprotein (P-gp) and cytochrome P450 3A4, both responsible for the disposition and metabolism of NOACs to a different extent. In this review/expert opinion, we focused on an extensive report of edoxaban DDIs. All the relevant drugs categories have been examined to report on significant DDIs, discussing the impact on edoxaban pharmacokinetics and pharmacodynamics, and the evidence for dose adjustment. Our analysis found that, despite a restrained number of interactions, some strong inhibitors/inducers of P-gp and drug-metabolising enzymes can affect edoxaban concentration, just as it happens with other NOACs, implying the need for a dose adjustment. However, our analysis of edoxaban DDIs suggests that given the small propensity for interactions of this agent, its use represents an acceptable clinical decision. Still, DDIs can be significant in certain clinical situations and a careful evaluation is always needed when prescribing NOACs.

Drug-drug interactions between vitamin K antagonists and statins: a systematic review

PURPOSE

Concomitant use of vitamin K antagonists (VKA) and statins is frequent in cardiovascular patients. However, clinical guidelines on this drug combination are divergent. Therefore, we performed a systematic review to evaluate the effect of statin initiation on coagulation among VKA users.

METHODS

Following the PRISMA guidelines, we applied two broad search strategies for the drug interaction between VKA and statins in both Embase and Pubmed; 8623 unique hits were obtained. In the final sample, eight studies were included.

RESULTS

The most frequently used VKA in the studies was warfarin, while simvastatin was the most commonly initiated statin. All included studies showed a minor increase in the anticoagulant effect of VKA following statin initiation during VKA treatment. The reported increases in mean international normalized ratio (INR) ranged from 0.15-0.65.

CONCLUSION

The anticoagulant effect of statin initiation in patients treated with VKA is likely to be of limited clinical relevance but should be evaluated individually.

Evaluation of serious bleeding signals during concomitant use of clopidogrel and hypnotic drugs

BACKGROUND

In a previous drug-drug interaction (DDI) screening study intended to generate hypotheses, clopidogrel + either eszopiclone or zolpidem (vs. clopidogrel alone) were associated with serious bleeding.

OBJECTIVES

To confirm or refute these DDI signals and examine associations with other hypnotics in an independent population of United States Medicaid beneficiaries METHODS: We employed a bi-directional self-controlled case series design in eligible individuals concomitantly exposed to one of 12 hypnotics (precipitants, exposures of interest) plus either clopidogrel (the object drug) or pravastatin (the negative control object drug). The outcome was hospital presentation with serious bleeding. Using conditional Poisson regression, we calculated confounder-adjusted rate ratios (RRs) and 95% confidence intervals for serious bleeding during clopidogrel + precipitant use (vs. clopidogrel alone). To distinguish a DDI from a precipitant's inherent effect on bleeding, we divided effect measures by the adjusted RR for the corresponding pravastatin + precipitant pair to obtain ratios of RR (RRRs).

RESULTS

Among 23,194 users of clopidogrel and 3824 of pravastatin who experienced serious bleeding during an active prescription for one of these agents, confounder-adjusted RRRs for serious bleeding were 6.63 (0.39-113.01) and 0.77 (0.53-1.11) with eszopiclone and zolpidem, respectively, whereas confounder-adjusted RRRs for other hypnotics ranged from 0.18 (0.04-0.85) for triazolam to 1.79 (0.16-20.44) for zaleplon. Statistical imprecision therefore precluded us from confirming or refuting these prior signals with eszopiclone and zolpidem.

CONCLUSIONS

While we could not confirm or refute previously identified DDI signals, numerically elevated RRRs for serious bleeding with several clopidogrel + hypnotic pairs warrant further examination.

Drug-drug Interactions with Warfarin: A Systematic Review and Meta-analysis

AIM

The objective of this paper is to systematically review the literature on drug-drug interactions with warfarin, with a focus on patient-important clinical outcomes.

METHODS

MEDLINE, EMBASE, and the International Pharmaceutical Abstract (IPA) databases were searched from January 2004 to August 2019. We included studies describing drug-drug interactions between warfarin and other drugs. Screening and data extraction were conducted independently and in duplicate. We synthesized pooled odds ratios (OR) with 95% confidence intervals (CIs), comparing warfarin plus another medication to warfarin alone. We assessed the risk of bias at the study level and evaluated the overall certainty of evidence using GRADE.

RESULTS

Of 42,013 citations identified, a total of 72 studies reporting on 3,735,775 patients were considered eligible, including 11 randomized clinical trials and 61 observational studies. Increased risk of clinically relevant bleeding when added to warfarin therapy was observed for antiplatelet (AP) regimens (OR=1.74; 95% CI 1.56, 1.94), many antimicrobials (OR=1.63; 95% CI 1.45, 1.83), NSAIDs including COX-2 NSAIDs (OR=1.83; 95% CI 1.29, 2.59), SSRIs (OR=1.62; 95% CI 1.42, 1.85), mirtazapine (OR=1.75; 95% CI 1.30, 2.36), loop diuretics (OR=1.92; 95% CI 1.29, 2.86), and others. We found a protective effect of proton pump inhibitors (PPIs) against warfarin-related gastrointestinal (GI) bleedings (OR=0.69; 95% CI 0.64, 0.73). No significant effect on thromboembolic events or mortality of any drug group used with warfarin was found, including single or dual AP regimens.

CONCLUSIONS

This review found low to moderate certainty evidence supporting the interaction between warfarin and a small group of medications, which result in increased bleeding risk. PPIs are associated with reduced hospitalization for upper GI bleeding for patients taking warfarin. Further studies are required to better understand drug-drug interactions leading to thromboembolic outcomes or death.

Frailty and Co-Prescribing of Potentially Interacting Drugs in New Users of Warfarin

Background

Warfarin is underutilised in frail older people because of the fear of bleeding complications. Drug interactions are an independent bleeding risk factor. However, the extent to which potential drug interactions are taken into account at warfarin therapy initiation in frail patients is not known.

Objective

The objective of this study was to investigate the use of potentially interacting drugs increasing the bleeding risk before and after warfarin initiation in frail and non-frail patients.

Methods

We conducted an observational study including inpatients aged ≥ 60 years initiated on warfarin in a tertiary hospital in Adelaide, South Australia. Frailty status was assessed with the Reported Edmonton Frail Scale. Medication charts were reviewed before and after warfarin initiation.

Results

In total, 151 patients (102 non-frail and 49 frail) were included. Before warfarin initiation, the use of clopidogrel and acetaminophen was more common in frail patients compared with non-frail patients (25.5% vs 10.2%, p = 0.0135, 63.8% vs 35.7% p = 0.0014, respectively). The use of non-steroidal anti-inflammatory drugs, 9.2% in non-frail patients and 6.4% in frail patients before warfarin initiation, was completely stopped after warfarin initiation in both groups. The use of antiplatelet drugs decreased from 56.1% in non-frail patients and 66.0 % in frail patients to 12.2% and 14.9%, respectively. Instead, the use of drugs affecting the metabolism of warfarin or vitamin K increased in both groups. No statistically significant difference was seen in the exposure to interacting drugs between study groups after warfarin initiation. Acetaminophen, senna glycosides and cytochrome P450 2C9 inhibiting drugs were the most common interacting drugs at discharge used in 49.0%, 18.4% and 20.4% of non-frail patients and 53.2%, 29.8% and 19.1% of frail patients, respectively.

Conclusions

The overall frequency of potential drug interactions was moderate and frail patients were not exposed to warfarin drug interactions more often than non-frail patients. Further studies in larger study populations are required to verify these results.

Electronic supplementary material

The online version of this article (10.1007/s40266-020-00755-0) contains supplementary material, which is available to authorized users.

Drug-drug interaction between warfarin and statins: A Danish cohort study

Initiation of statin treatment is suggested to increase the international normalised ratio (INR) among warfarin users. However, available data is limited and conflicting. We conducted a register-based cohort study to evaluate the drug-drug interaction between warfarin and statins. By linking data on INR measurements and filled prescriptions, we identified warfarin users 2000-2015 initiating simvastatin (n = 1363), atorvastatin (n = 165) or rosuvastatin (n = 23). Simvastatin initiation led to an increase in mean INR from 2.40 to 2.71, with INRs peaking after 4 weeks, corresponding to a mean change of 0.32 (95%CI 0.25-0.38). High-dose and low-dose simvastatin led to comparable changes (mean change 0.33 vs 0.29). Initiation of atorvastatin and rosuvastatin lead to INR increases of 0.27 (95%CI 0.12-0.42) and 0.30 (95%CI -0.09-0.69). In conclusion, initiation of simvastatin, atorvastatin or rosuvastatin among warfarin users led to a minor increase in INR. The magnitude of this change is for most patients likely of limited clinical relevance.

Sulfonylureas and Metformin Were Not Associated With an Increased Rate of Serious Bleeding in Warfarin Users: A Self-Controlled Case Series Study

Drug interactions between warfarin and sulfonylureas are suggested by pharmacokinetic information and prior studies. However, clinical evidence on the association of such interactions and the risk of bleeding is lacking. Using healthcare claims data from 5 US Medicaid programs from 1999-2011 and a self-controlled case series design with warfarin as an object drug, we calculated confounder-adjusted rate ratios (RRs) for concomitant use of sulfonylureas and metformin for 3 outcomes separately: (i) serious bleeding as a composite outcome of gastrointestinal bleeding (GIB) and nontraumatic intracranial hemorrhage (ICH); (ii) GIB; and (iii) ICH. In 6,463 warfarin users experiencing serious bleeding, an increased rate of serious bleeding was not associated with concomitant use of glimepiride (RR: 0.93; 95% confidence interval (CI) 0.75-1.15), glipizide (RR: 0.97; 95% CI 0.84-1.13), glyburide (RR: 0.89; 95% CI 0.76-1.06), or metformin (RR: 0.85; 95% CI 0.76-0.96), nor was the occurrence of the component outcomes of GIB or ICH. These results suggest that use of sulfonylureas or metformin was not associated with an increased rate of serious bleeding in warfarin users.

Evaluation of the US Food and Drug Administration Sentinel Analysis Tools Using a Comparator with a Different Indication: Comparing the Rates of Gastrointestinal Bleeding in Warfarin and Statin Users

BACKGROUND

The US Food and Drug Administration's Sentinel System was established to monitor safety of regulated medical products. Sentinel investigators identified known associations between drugs and adverse events to test reusable analytic tools developed for Sentinel. This test case used a comparator with a different indication.

OBJECTIVE

We tested the ability of Sentinel's reusable analytic tools to identify the known association between warfarin and gastrointestinal bleeding (GIB). Statins, expected to have no effect on GIB, were the comparator. We further explored the impact of analytic features, including matching ratio and stratifying Cox regression analyses, on matched pairs.

METHODS

This evaluation included data from 14 Sentinel Data Partners. New users of warfarin and statins, aged 18 years and older, who had not received other anticoagulants or had recent GIB were matched on propensity score using 1:1 and 1:n variable ratio matching, matching statin users with warfarin users to estimate the average treatment effect in warfarin-treated patients. We compared the risk of GIB using Cox proportional hazards regression, following patients for the duration of their observed continuous treatment or until a GIB. For the 1:1 matched cohort, we conducted analyses with and without stratification on matched pair. The variable ratio matched cohort analysis was stratified on the matched set.

RESULTS

We identified 141,398 new users of warfarin and 2,275,694 new users of statins. In analyses stratified on matched pair/set, the hazard ratios (HR) for GIB in warfarin users compared with statin users were 2.78 (95% confidence interval [CI] 2.36-3.28) in the 1:1 matched cohort and 3.10 (95% CI 2.76-3.49) in the variable ratio matched cohort. The HR was lower in the analysis of the 1:1 matched cohort not stratified by matched pair (2.22, 95% CI 1.97-2.49), and highest early in treatment. Follow-up for warfarin users tended to be shorter than for statin users.

CONCLUSIONS

This study identified the expected GIB risk with warfarin compared with statins using an analytic tool developed for Sentinel. Our findings suggest that comparators with different indications may be useful in surveillance in select circumstances. Finally, in the presence of differential censoring, stratification by matched pair may reduce the potential for bias in Cox regression analyses.

Clopidogrel Drug Interactions and Serious Bleeding: Generating Real-World Evidence via Automated High-Throughput Pharmacoepidemiologic Screening

Few population-based studies have examined bleeding associated with clopidogrel drug-drug interactions (DDIs). We sought to identify precipitant drugs taken concomitantly with clopidogrel (an object drug) that increased serious bleeding rates. We screened 2000-2015 Optum commercial health insurance claims to identify DDI signals. We performed self-controlled case series studies for clopidogrel plus precipitant pairs, examining associations with gastrointestinal bleeding or intracranial hemorrhage. To distinguish native bleeding effects of a precipitant, we reexamined associations using pravastatin as a negative control object drug. Among 431 analyses, 28 clopidogrel plus precipitant pairs were statistically significantly positively associated with serious bleeding. Ratios of rate ratios ranged from 1.13-3.94. Among these pairs, 13 were expected given precipitant drugs alone increased and/or were harbingers of serious bleeding. The remaining 15 pairs constituted new DDI signals, none of which are currently listed in two major DDI knowledge bases.

Statins and the risk of bleeding in patients taking dabigatran

OBJECTIVES

Dabigatran etexilate is a direct thrombin inhibitor that clinicians increasingly prescribe to prevent stroke in patients with non-valvular atrial fibrillation (NVAF). Clinicians also commonly prescribe statins for primary and secondary prevention of cardiovascular diseases. Little is known about the bleeding risk in patients taking a statin and dabigatran together. The aim of this study was to evaluate the safety and persistence of dabigatran after co-medication with statins.

MATERIALS AND METHODS

We performed a prospective, multicenter registry study of stroke patients with NVAF who initiated dabigatran therapy within 3 months after a clinically evident ischemic cerebrovascular event between 2013 and 2017. The main outcome measure was symptomatic bleeding after 90, 180, and 360 days.

RESULTS

In total, 652 patients (336 statin users, 316 non-users) were followed for 1 year after dabigatran therapy. Cox multivariate analysis demonstrated that male sex, prior use of aspirin, and concurrent use of an antiarrhythmic drug were associated with a higher risk of bleeding at 360 days. After adjusting time-dependent covariates, statin users had a significantly lower bleeding risk (adjusted hazard ratio: 0.11, P < 0.001) than non-users. Kaplan-Meier analysis indicated that patients prescribed with statins had a higher rate of bleeding-free survival (P = 0.028).

CONCLUSION

For secondary prevention of stroke in patients with NVAF who are taking dabigatran etexilate, co-prescription with a statin was associated with a lower risk of bleeding complications. Future research is needed to determine the pharmacological mechanism underlying this effect.

Statin Use and Gastrointestinal Hemorrhage: A Large Retrospective Cohort Study

BACKGROUND

Nearly 70% of Americans with cardiovascular disease use statins, which have documented bleeding effects independent of their cholesterol-lowering activities. However, the literature is conflicting regarding the association between statin use and gastrointestinal hemorrhage.

OBJECTIVES

The aim of this study was to investigate the risk of gastrointestinal hemorrhage in statin users.

METHODS

In this retrospective cohort study, data from the Truven Health MarketScan^® Research Database (2009-2015) were used to investigate the risk of gastrointestinal hemorrhage amongst statin users aged 30-65 years at the initial prescription claim. Statin users and a group of negative controls (i.e. other chronic medication users) were followed until first gastrointestinal hemorrhage event (both inpatient and outpatient, as well as restricted to inpatient), and were censored at treatment discontinuation, disenrollment from coverage, or the end of the study period.

RESULTS

Statin users had an elevated risk of gastrointestinal hemorrhage, which was especially apparent in the first year of treatment (1-year adjusted hazard ratio 1.19; 95% confidence interval (CI) 1.15-1.23). The risk of gastrointestinal hemorrhage leading to hospitalization was even higher (1-year adjusted hazard ratio 1.38; 95% CI 1.30-1.69). High-intensity statin users had a greater rate of gastrointestinal hemorrhage than moderate-intensity users (incidence rates per 1000 subject-years 22.2 (95% CI 21.9-22.8) vs. 21.5 (95% CI 21.3-21.8), respectively).

CONCLUSIONS

In a population of commercially insured subjects aged 30-65 years, statin users had a higher risk for gastrointestinal hemorrhage than other chronic medication users. These findings are important when treating patients at a high risk for bleeding events.

Statins and gastroduodenal endoscopic lesions: A case-control study

Experimental studies showed a dose-dependent gastroprotective effect of statins on non-steroidal anti-inflammatory drug-induced endoscopic lesions, modulated by increasing endogenous nitric oxide and prostaglandin production.We investigated the influence of chronic treatment with statins on the occurrence of endoscopic lesions in patients referred for endoscopic evaluation, adjusted for the most important etiologic and risk factors for peptic ulcer disease and its complications.A consecutive series of 564 patients who underwent upper digestive endoscopy, stratified according to the severity of endoscopic lesions were recruited. Patients with statin therapy were included in the study group (n = 220), while patients without statins in the control group (n = 344). We correlate the influence of chronic statin therapy (at least 6 months) with factors including age up to 50 years, Helicobacter pylori infection, smoking and drinking habits, ulcer history, gastrotoxic drug consumption (low-dose aspirin [ASA], anticoagulants), and comorbidities.H pylori infection was more frequent in patients with mild/severe endoscopic lesions vs. no lesions, in both groups, but the difference was not statistically significant (P >.05). Male gender represented a risk factor (P <.01) for mild/severe endoscopic lesions only in the statin group. The estimated risk for developing mild/severe endoscopic lesions with ASA intake decreased from 6.26 to 3.40 (P <.01) when statin therapy was associated. Patients without statins and ischemic coronary artery disease (P <.01; odds ratio [OR] = 2.99; 95% confidence interval (CI):1.88-4.73), heart failure (P = .01; OR = 2.13; 95% CI:1.36-3.34), systemic atherosclerosis (P = .04; OR = 2.30; 95% CI:1.44-3.67) had a statistically significant increased risk for developing mild/severe endoscopic lesions in comparison with patients in the statin group. In multivariate regression analysis models, smoking (P <.01; OR = 2.69; 95% CI:1.73-4.16), ASA (P <.01; OR = 4.54; 95% CI:2.83-7.16), and coronary artery diseases (P = .01; OR = 1.80; 95% CI:1.15-2.82) were independent risk factors for mild/severe endoscopic lesions, while chronic statin therapy (P <.01; OR = 0.31; 95% CI:0.19-0.51) was associated with a protective effect in all models.The results of the present study support a certain protective role of chronic therapy with statins against endoscopic lesions, especially in ASA consumers or patients with cardiovascular diseases.

The Role of Clinical Variables and VKORC1 Polymorphism in Efficacy and Stability of Acenocoumarol in Neurological Patients

Objective:

To analyze the clinical importance of VKORC1 polymorphism and its correlation with stability of oral anticoagulation.

Patients and Methods:

In a hospital-based study, the patients on oral anticoagulant (OAC) were included during 2013–2016. The patients received OAC for cardioembolic stroke, cerebral venous sinus thrombosis (CVST), and prevention of deep vein thrombosis (DVT). Demographic, clinical, and neurological findings were recorded. Stability of anticoagulation was determined by percentage of time international normalized ratio (INR) values were in therapeutic range. Time in therapeutic range (TTR) >65% was defined as stable and <65% was defined unstable. VKORC 1 polymorphism was studied by polymerase chain reaction and correlated with daily dose of OAC and stability of INR.

Results:

A total of 157 patients with a median age of 40 years were included in the study. Ninety-two patients received OAC for secondary stroke prevention, 62 for CVST, and 3 for DVT. Out of 2976 INR reports, 1458 (49%) were in the therapeutic range, 997 (33.1%) were below the therapeutic range, and 521 (17.5%) were above the therapeutic level. Stable INR was obtained in 75 (47.77%) patients which was improved by drug modification in 3 and dietary adjustment in 12 patients. VKORC1 polymorphism revealed GG genotype in 127 (80.9%), GA genotype in 22 (14%), and AA genotype in 8 (5.1%) patients. Therapeutic range of INR was seen in 49%, below therapeutic range was seen in 31.5%, and above in 17.5%.

Conclusion:

VKORC1 polymorphism was related to mean daily dose of OAC but not to the stability of INR.

Long-Term Statin Administration Does Not Affect Warfarin Time in Therapeutic Range in Australia or Singapore

BACKGROUND

Warfarin requires ongoing monitoring of the International Normalised Ratio (INR). This is because numerous factors influence the response, including drug interactions with commonly-prescribed medications, such as statins. The administration of statins with warfarin may change INR; however, there is limited information regarding the effects on warfarin control as measured by time in therapeutic range (TTR). Statins may also alter bleeds with warfarin, but there are conflicting reports demonstrating both increased and decreased bleeds, and limited data on diverse ethnic populations. Therefore, the aim of this study was to determine the effect of statin administration on warfarin control and bleeds in patients in Australia and Singapore.

METHODS

Retrospective data were collected for patients on warfarin between January and June 2014 in Australia and Singapore. Patient data were used to calculate TTR and bleed events. Concurrent statin therapy was assessed and comparisons of TTR and bleed incidence were made across patient subgroups.

RESULTS

Warfarin control in Australia and Singapore was not significantly affected by statins, as measured by TTR (83% and 58%, respectively), frequency of testing, and warfarin doses. In Australia, statin use did not significantly affect bleeds, whilst in Singapore the bleed incidence was significantly lower for patients on statins.

CONCLUSIONS

Chronic concurrent administration of statins with warfarin does not adversely affect warfarin TTR in Australia or Singapore. In Singapore, patients on statins, compared to no statins, had a lower bleed incidence and this requires further investigation, especially given the potential genetic influences of ethnicity on both statin and warfarin metabolism.

The influence of fibrate initiation on INR and warfarin dose in patients receiving chronic warfarin therapy

Several drug interaction compendia report a risk of warfarin potentiation after initiation of a fibrate; however, the evidence of this interaction is limited. The objective of this study was to evaluate warfarin dose and international normalized ratio (INR) response among a large sample of patients receiving chronic warfarin who initiated a fibrate. This was a retrospective, one-sample, pre-to-post study. Adult patients who were receiving chronic warfarin therapy at the time of gemfibrozil or fenofibrate dispensing between 1/1/2000 and 3/31/2016 were included. Patients had at least one and two therapeutic INRs during the 90 days prior to (baseline) and after (follow-up), respectively, fibrate initiation. Comparison of stable warfarin dose:INR ratio between the baseline and follow-up periods and assessment of safety outcomes during follow-up were performed. There were 321 patients included. Patients were predominantly male (62.6%) with an indication of atrial fibrillation (44.2%). The mean warfarin dose:INR ratio was equivalent between the baseline and follow-up periods (13.4 mg/INR [± 6.9] vs. 13.5 mg/INR [± 7.5], respectively, p = 0.711). Rates of thromboembolism, bleeding, and all-cause mortality in the 90-day follow up were 0, 0.6, and 1.2%, respectively. Although individual patients may have labile INRs after fibrate initiation, no significant interaction between fibrate and warfarin in a large sample of real world patients was identified. The utility of additional INR monitoring after fibrate initiation in otherwise stable patients receiving chronic warfarin therapy is unclear.

Nonsteroidal anti-inflammatory drug choice and adverse outcomes in clopidogrel users: A retrospective cohort study

Objective

To examine the comparative safety of individual NSAIDs when given concomitantly with clopidogrel.

Methods

We conducted a retrospective cohort study using Medicaid claims from five US states during 1999–2010, supplemented with Medicare claims for dual-enrollees. The exposure of interest was the first concomitant use of clopidogrel and one of the 10 selected NSAIDs after a 1-year baseline period. The outcomes were: all-cause mortality; acute myocardial infarction (AMI)/ischemic stroke; and gastrointestinal bleeding (GIB)/intracranial hemorrhage (ICH). We calculated the hazard ratio of each NSAID for each outcome, with ibuprofen as the reference drug, using high-dimensional propensity score-adjusted proportional-hazards regression models.

Results

Of 1,060,412 clopidogrel users, 268,114 concomitant NSAID users met inclusion/exclusion criteria, contributing 48,483 person-years. We observed 2,463 deaths, 2,822 AMI/ischemic stroke outcomes, and 2,620 GIB/ICH outcomes, for unadjusted incidence rates of 50.8, 58.6, and 54.3 per 1,000 person-years, respectively. Compared with ibuprofen and controlling for potential confounders, rofecoxib (hazard ratio [HR] = 1.22; 95% confidence interval [CI]: 1.04, 1.43) and valdecoxib (HR = 0.66; 95% CI: 0.48, 0.92) showed higher and lower hazards of mortality, respectively. Indomethacin showed an increased AMI/ischemic stroke hazard (HR = 1.38; 95% CI: 1.09, 1.74). For GIB/ICH, indomethacin (HR = 2.18; 95% CI: 1.74, 2.73), diclofenac (HR = 1.65; 95% CI: 1.39, 1.97), naproxen (HR = 1.47; 95% CI: 1.28, 1.70), and rofecoxib (HR = 1.26; 95% CI: 1.08, 1.48) showed higher hazards, and valdecoxib (HR = 0.73; 95% CI: 0.55, 0.98) showed a lower hazard.

Conclusion

The bleeding risks of individual NSAIDs varied more markedly than thrombotic risks when used concomitantly with clopidogrel. Moreover, bleeding risk and thrombotic risk among individual NSAIDs did not appear to be inversely related to each other in the presence of clopidogrel. Further studies are needed to elucidate underlying biological mechanisms and help clinical decision-making for a better NSAID choice in clopidogrel users.

The quality of Medicaid and Medicare data obtained from CMS and its contractors: implications for pharmacoepidemiology

Background

Administrative claims of United States Centers for Medicare and Medicaid Services (CMS) beneficiaries have long been used in non-experimental research. While CMS performs in-house checks of these claims, little is known of their quality for conducting pharmacoepidemiologic research. We performed exploratory analyses of the quality of Medicaid and Medicare data obtained from CMS and its contractors.

Methods

Our study population consisted of Medicaid beneficiaries (with and without dual coverage by Medicare) from California, Florida, New York, Ohio, and Pennsylvania. We obtained and compiled 1999–2011 data from these state Medicaid programs (constituting about 38% of nationwide Medicaid enrollment), together with corresponding national Medicare data for dually-enrolled beneficiaries. This descriptive study examined longitudinal patterns in: dispensed prescriptions by state, by quarter; and inpatient hospitalizations by federal benefit, state, and age group. We further examined discrepancies between demographic characteristics and disease states, in particular frequencies of pregnancy complications among men and women beyond childbearing age, and prostate cancers among women.

Results

Dispensed prescriptions generally increased steadily and consistently over time, suggesting that these claims may be complete. A commercially-available National Drug Code lookup database was able to identify the dispensed drug for 95.2–99.4% of these claims. Because of co-coverage by Medicare, Medicaid data appeared to miss a substantial number of hospitalizations among beneficiaries ≥ 45 years of age. Pregnancy complication diagnoses were rare in males and in females ≥ 60 years of age, and prostate cancer diagnoses were rare in females.

Conclusions

CMS claims from five large states obtained directly from CMS and its contractors appeared to be of high quality. Researchers using Medicaid data to study hospital outcomes should obtain supplemental Medicare data on dual enrollees, even for non-elders.

Trial Registration

Not applicable.

Electronic supplementary material

The online version of this article (doi:10.1186/s12913-017-2247-7) contains supplementary material, which is available to authorized users.

Improving medical record retrieval for validation studies in Medicare data

PURPOSE

The purpose of the study is to describe medical record retrieval for a study validating claims-based algorithms used to identify seven adverse events of special interest (AESI) in a Medicare population.

METHODS

We analyzed 2010-2011 Medicare claims of women with postmenopausal osteoporosis and men ≥65 years of age in the Medicare 5% national sample. The final cohorts included beneficiaries covered continuously for 12+ months by Medicare parts A, B, and D and not enrolled in Medicare Advantage before starting follow-up. We identified beneficiaries using each AESI algorithm and randomly selected 400 women and 100 men with each AESI for medical record retrieval. The Centers for Medicare and Medicaid Services provided beneficiary contact information, and we requested medical records directly from providers, without patient contact.

RESULTS

We selected 3331 beneficiaries (women: 2272; men: 559) for whom we requested 3625 medical records. Overall, we received 1738 [47.9% (95%CI 46.3%, 49.6%)] of the requested medical records. We observed small differences in the characteristics of the total population with AESIs compared with those randomly selected for retrieval; however, no differences were seen between those selected and those retrieved. We retrieved 54.7% of records requested from hospitals compared with 26.3% of records requested from physician offices (p < 0.001). Retrieval did not differ by sex or vital status of the beneficiaries.

CONCLUSIONS

Our national medical record validation study of claims-based algorithms produced a modest retrieval rate. The medical record procedures outlined in this paper could have led to the improved retrieval from our previous medical record retrieval study. Copyright © 2016 John Wiley & Sons, Ltd.

CE: Triglycerides: Do They Matter?

: Since the introduction of HMG-CoA reductase inhibitors, also known as statins, as an adjunct to diet in the treatment of hyperlipidemia and the greater emphasis placed on reducing low-density lipoprotein (LDL) cholesterol levels in the prevention of atherosclerosis and cardiovascular disease (CVD), there has been less focus on the value of lowering serum triglyceride levels. Many patients are aware of their "good" and "bad" cholesterol levels, but they may not be aware of their triglyceride level or of the association between high triglycerides and the development of CVD. In recent years, however, in light of the increasing incidences of obesity, insulin resistance, and type 2 diabetes, lowering triglyceride levels has gained renewed interest. In addition to the focus on lowering LDL cholesterol levels in CVD prevention, clinicians need to be aware of the role of triglycerides-their contribution to CVD, and the causes and treatment of hypertriglyceridemia.

VKORC1 and CYP2C9 polymorphisms related to adverse events in case-control cohort of anticoagulated patients

Vitamin K antagonists (VKAs) are highly effective but have a narrow therapeutic index and require routine monitoring of the INR. The primary aim of pharmacogenetics (PGx) is to optimize patient care, achieving drug treatments that are personalized according to the genetic profile of each patient. The best-characterized genes involved in VKA PGx involve pharmacokinetics (VKORC1) and pharmacodynamics (CYP2C9) of VKA metabolism. The role of these genes in clinical outcomes (bleeding and thrombosis) during oral anticoagulant (OAC) therapy is controversial. The aim of the present study was to evaluate any potential association between genotype VKORC1 and CYP2C9 and adverse events (hemorrhagic and/or thrombotic), during initiation and long-term VKA treatment, in Caucasian patients. Furthermore, we aimed to determine if the concomitant prescription of other selected drugs affected the association between genotype and adverse events.We performed a retrospective, matched case-control study to determine associations between multiple gene variants, drug intake, and any major adverse effects in anticoagulated patients, monitored in 2 Italian anticoagulation clinics.Our results show that anticoagulated patients have a high risk of adverse events if they are carriers of 1 or more genetic polymorphisms in the VKORC1 (rs9923231) and CYP2C9 (rs1799853 and rs1057910) genes.Information on CYP2C9 and VKORC1 variants may be useful to identify individualized oral anticoagulant treatment for each patient, improve management and quality of VKA anticoagulation control, and monitor drug surveillance in pharmacovigilance programs.

Gastrointestinal bleeding and intracranial hemorrhage in concomitant users of warfarin and antihyperlipidemics

BACKGROUND

Drug interactions, particularly those involving warfarin, are a major clinical and public health problem. Minimizing serious bleeding caused by anticoagulants is a recent major focus of the United States (US) Department of Health and Human Services. This study quantified the risk of gastrointestinal bleeding (GIB) and intracranial hemorrhage (ICH) among concomitant users of warfarin and individual antihyperlipidemics.

METHODS

The authors conducted a high-dimensional propensity score-adjusted cohort study of new concomitant users of warfarin and an antihyperlipidemic, among US Medicaid beneficiaries from five states during 1999-2011. Exposure was defined by concomitant use of warfarin plus one of eight antihyperlipidemics. The primary outcome measure was a composite of GIB/ICH within the first 30days of concomitant use. As a secondary outcome measure, GIB/ICH was examined within the first 180days of concomitant use.

RESULTS

Among 236,691 persons newly-exposed to warfarin and an antihyperlipidemic, the crude incidence of GIB/ICH was 13.2 (95% confidence interval 12.7 to 13.8) per 100person-years. Users were predominantly older, female, and Caucasian. Adjusted hazard ratios (aHRs) for warfarin and individual statins were consistent with no association. Warfarin+gemfibrozil was associated with an 80% increased risk of GIB/ICH within the first month of concomitant use (aHR=1.8, 1.4 to 2.4). Warfarin+fenofibrate was associated with a similar increased risk (aHR=1.8, 1.2 to 2.7), yet with an onset during the second month of concomitant use.

CONCLUSIONS

Among warfarin-treated persons, the use of fibrates-but not statins-increases the risk of hospital presentation for GIB/ICH.

Analysis of the first therapeutic-target-achieving time of warfarin therapy and associated factors in patients with pulmonary embolism

The present study aimed to investigate the factors affecting the first therapeutic-target-achieving (TTA) time of warfarin therapy in patients with acute pulmonary embolism (PTE). Between January 2008 and June 2013, patients with PTE confirmed by transpulmonary arterial enhanced computed tomographic pulmonary angiography or pulmonary ventilation perfusion scanning were included in the present study. Data collected included demographic information, history of tobacco and alcohol intake, basic diseases (stable and unstable hypertension, diabetes, heart failure, cancer/cerebral infarction, old myocardial infarction and atrial fibrillation), liver and kidney function, the haemoglobin and platelet count of the blood, international normalized ratio monitoring, warfarin dosage adjustment and medication combinations. Dynamic changes in international normalized ratio, anticoagulant efficacy, and adverse events within 90 days were monitored and analyzed. Univariate analysis demonstrated that the following factors affect the first TTA time: Initial dose, body mass index (BMI), liver function, heart failure, and the administration of levofloxacin, cephalosporins, and blood circulation-activating drugs. Logistic regression analysis revealed that the following were independent factors of the first TTA time: Initial dose, BMI, liver function, heart failure and levofloxacin. Therefore, the results of the present study demonstrated that various factors may affect the first TTA time of warfarin therapy, including the initial dose, BMI, liver function, heart function and concomitant medication.

Comparison of the Risk of Gastrointestinal Bleeding among Different Statin Exposures with Concomitant Administration of Warfarin: Electronic Health Record-Based Retrospective Cohort Study

Background and Objective

Patients who should be treated with both warfarin and a statin are frequently seen in vascular clinics. The risk for bleeding and potential drug interactions should be considered when prescribing both medications together. This study aimed to compare the risk for gastrointestinal bleeding among different statin exposures with concomitant administration of warfarin.

Materials and Methods

This is a single-hospital retrospective cohort study. We included patients who were concomitantly exposed to one of four statins (pravastatin, simvastatin, atorvastatin, and rosuvastatin) and warfarin for up to 2 years (730 days). The observation period ended when a gastrointestinal bleeding event occurred or the observation was censored. Within-class comparisons were used, and 1:1 matching using a propensity score was performed for comparisons between each statin and all of the other statins. Kaplan-Meier analyses with log-rank tests and Cox proportional hazard regression analyses were conducted to determine associations with the risk of gastrointestinal bleeding.

Results

Data were analyzed for 1,686 patients who were concomitantly administered a statin and warfarin. Log-rank tests for the gastrointestinal bleeding-free survival rate showed that the risk for gastrointestinal bleeding was significantly lower in the pravastatin group (p = 0.0499) and higher in the rosuvastatin group (p = 0.009). In the Cox proportional hazard regression analysis, the hazard ratio of 5.394 for gastrointestinal bleeding based on statin exposure in the rosuvastatin group was significant (95% confidence interval, 1.168–24.916).

Conclusions

There was a relatively high risk of gastrointestinal bleeding with rosuvastatin when administered concomitantly with warfarin.

Mechanism of Drug-Drug Interactions Between Warfarin and Statins

The anticoagulant drug warfarin and the lipid-lowering statin drugs are commonly co-administered to patients with cardiovascular diseases. Clinically significant drug-drug interactions (DDIs) between these drugs have been recognized through case studies for many years, but the biochemical mechanisms causing these interactions have not been explained fully. Previous theories include kinetic alterations in cytochrome P-450-mediated drug metabolism or disturbances of drug-protein binding, leading to anticoagulant activity of warfarin; however, neither the enantioselective effects on warfarin metabolism nor the potential disruption of drug transporter function have been well investigated. This study investigated the etiology of the DDIs between warfarin and statins. Liquid chromatography-mass spectrometry methods were developed and validated to quantify racemic warfarin, 6 of its hydroxylated metabolites, and pure enantiomers of warfarin; these methods were applied to study the role of different absorption, distribution, metabolism, and excretion properties, leading to DDIs. Plasma protein binding displacement of warfarin was performed in the presence of statins using equilibrium dialysis method. Substrate kinetics of warfarin and pure enantiomers were performed with human liver microsomes to determine the kinetic parameters (Km and Vmax) for the formation of all 6 hydroxywarfarin metabolites, inhibition of warfarin metabolism in the presence of statins, was determined. Uptake transport studies of warfarin were performed using overexpressing HEK cell lines and efflux transport using human adenocarcinoma colonic cell line cells. Fluvastatin significantly displaced plasma protein binding of warfarin and pure enantiomers; no other statin resulted in significant displacement of warfarin. All the statins that inhibited the formation of 10-hydroxywarfarin, atorvastatin, pitavastatin, and simvastatin were highly potent compared to other statins; in contrast, only fluvastatin was found to be a potent inhibitor of formation of 7-hydroxy warfarin. Uptake and efflux drug transporters do not play any role in these DDIs. The results showed that DDIs between warfarin and statins are primarily caused by cytochrome P-450 inhibition.

Incidence rate and pattern of clinically relevant potential drug-drug interactions in a large outpatient population of a developing country

The objective of this study was to determine incidence rate, type, and pattern of clinically relevant potential drug-drug interactions (pDDIs) in a large outpatient population of a developing country. A retrospective, descriptive cross-sectional study was conducted on outpatients' prescriptions in Khorasan Razavi province, Iran, over 12 months. A list of 25 clinically relevant DDIs, which are likely to occur in the outpatient setting, was used as the reference. Most frequent clinically relevant pDDIs, most common drugs contributing to the pDDIs, and the pattern of pDDIs for each medical specialty were determined. Descriptive statistics were used to report the results. In total, out of 8,169,142 prescriptions, 6,096 clinically relevant pDDIs were identified. The most common identified pDDIs were theophyllines-quinolones, warfarin-nonsteroidal anti-inflammatory drugs, benzodiazepines-azole antifungal agents, and anticoagulants-thyroid hormones. The most common drugs contributing to the identified pDDIs were ciprofloxacin, theophylline, warfarin, aminophylline, alprazolam, levothyroxine, and selegiline. While the incidence rate of clinically relevant pDDIs in prescriptions of general practitioners, internists, and cardiologists was the highest, the average pDDI incidence per 10,000 prescriptions of pulmonologists, infectious disease specialists, and cardiologists was highest. Although a small proportion of the analyzed prescriptions contained drug pairs with potential for clinically relevant DDIs, a significant number of outpatients have been exposed to the adverse effects associated with these interactions. It is recommended that in addition to training physicians and pharmacists, other effective interventions such as computerized alerting systems and electronic prescribing systems be designed and implemented.

Pharmacoepidemiologic Methods for Studying the Health Effects of Drug-Drug Interactions

A drug-drug interaction (DDI) occurs when one or more drugs affect the pharmacokinetics (the body's effect on the drug) and/or pharmacodynamics (the drug's effect on the body) of one or more other drugs. Pharmacoepidemiologic studies are the principal way of studying the health effects of potential DDIs. This article discusses aspects of pharmacoepidemiologic research designs that are particularly salient to the design and interpretation of pharmacoepidemiologic studies of DDIs.

The effect of statins on the occurrence of peptic ulcer

BACKGROUND

This study was to determine the association between the use of statins and the occurrence of peptic ulcer diseases (PUD).

METHODS

Using the National Health Insurance Research Database to conduct a population-based cohort study. We identified 48,562 patients who were newly diagnosed with hyperlipidemia during the period of 1998 to 2011 and who were divided into two groups based on their use of statins. The non-statin cohort (without statin treatment, 24,139 patients) were 1:1 frequency matched with sex, age, year of diagnosis of hyperlipidemia and index-year to the statin cohort (24,423 patients). The relative risk of patients with and without statins treatment on the occurrence of PUD and concomitant use of nonsteroidal anti-inflammatory drugs (NSAIDs) and aspirin were analyzed using the univariable and multivariable Cox proportional hazards regression model.

RESULTS

The incidence of PUD increased with age in both cohorts and female had a higher occurrence rate than male in both cohorts. Compared with the non-statin cohort, the statin cohort was associated with a significant lower risk of PUD for all age group. The concomitant use of aspirin and/or NSAIDs had higher incidence of PUD than those without in both cohorts. Analyzing the cumulative defined daily dose (DDD) of statins indicated that high-dose groups (≧ 575 DDD) exhibited significantly decreased risk compared with non-statin users.

CONCLUSION

The results of the present study indicated that statins might be associated with the protection of peptic ulcer in a dose-respondent manner.

Comparative risk of ischemic stroke among users of clopidogrel together with individual proton pump inhibitors

BACKGROUND AND PURPOSE

There is controversy and little information about whether individual proton pump inhibitors (PPIs) differentially alter the effectiveness of clopidogrel in reducing ischemic stroke risk. We, therefore, aimed to elucidate the risk of ischemic stroke among concomitant users of clopidogrel and individual PPIs.

METHODS

We conducted a propensity score-adjusted cohort study of adult new users of clopidogrel, using 1999 to 2009 Medicaid claims from 5 large states. Exposures were defined by prescriptions for esomeprazole, lansoprazole, omeprazole, rabeprazole, and pantoprazole-with pantoprazole serving as the referent. The end point was hospitalization for acute ischemic stroke, defined by International Classification of Diseases Ninth Revision Clinical Modification codes in the principal position on inpatient claims, within 180 days of concomitant therapy initiation.

RESULTS

Among 325 559 concomitant users of clopidogrel and a PPI, we identified 1667 ischemic strokes for an annual incidence of 2.4% (95% confidence interval, 2.3-2.5). Adjusted hazard ratios for ischemic stroke versus pantoprazole were 0.98 (0.82-1.17) for esomeprazole; 1.06 (0.92-1.21) for lansoprazole; 0.98 (0.85-1.15) for omeprazole; and 0.85 (0.63-1.13) for rabeprazole.

CONCLUSIONS

PPIs of interest did not increase the rate of ischemic stroke among clopidogrel users when compared with pantoprazole, a PPI thought to be devoid of the potential to interact with clopidogrel.

Co-Prescribing of Potentially Interacting Drugs during Warfarin Therapy - A Population-Based Register Study

We analysed the occurrence of co-prescribing of potentially interacting drugs during warfarin therapy in the community-dwelling population of Finland. We identified drugs having interaction potential with warfarin using the Swedish Finnish INteraction X-referencing drug-drug interaction database (SFINX) and obtained data on drug purchases from the nationwide Prescription Register. We defined warfarin users as persons purchasing warfarin in 2010 (n = 148,536) and followed them from their first prescription in 2010 until the end of the calendar year. Co-prescribing was defined as at least 1-day overlap between warfarin and interacting drug episodes. In addition, we identified persons who initiated warfarin therapy between 1 January 2007 and 30 September 2010 (n = 110,299) and followed these incident users for a 3-month period since warfarin initiation. Overall, 74.4% of warfarin users were co-prescribed interacting drugs. Co-prescribing covered 46.4% of the total person-years of warfarin exposure. Interacting drugs that should be avoided with warfarin were co-prescribed for 13.4% of warfarin users. The majority of the co-prescriptions were for drugs that are not contraindicated during warfarin therapy but require special consideration. Among incident users, 57.1% purchased potentially interacting drugs during the 3-month period after initiation, while 9.0% purchased interacting drugs that should be avoided with warfarin. To conclude, the occurrence of co-prescribing of potentially interacting drugs was high during warfarin therapy. Our findings highlight the importance of close monitoring of warfarin therapy and the need for further studies on the clinical consequences of co-prescribing of interacting drugs with warfarin.

Improving postapproval drug safety surveillance: getting better information sooner

Adverse drug events (ADEs) are an important public health concern, accounting for 5% of all hospital admissions and two-thirds of all complications occurring shortly after hospital discharge. There are often long delays between when a drug is approved and when serious ADEs are identified. Recent and ongoing advances in drug safety surveillance include the establishment of government-sponsored networks of population databases, the use of data mining approaches, and the formal integration of diverse sources of drug safety information. These advances promise to reduce delays in identifying drug-related risks and in providing reassurance about the absence of such risks.

Anticoagulation for noncardiac indications in neurologic patients: comparative use of non-vitamin k oral anticoagulants, low-molecular-weight heparins, and warfarin

OPINION STATEMENT

Patients with neurologic disorders may develop a wide variety of thromboembolic events, both as a primary manifestation and as a consequence of their underlying neurologic condition. There are many available options for anticoagulation, ranging from warfarin to the parenteral subcutaneously administered anticoagulants to the non-vitamin K oral anticoagulants (NOACs). Warfarin is orally available, well-studied, and easily reversible in the setting of bleeding, but has a prolonged onset of action, measured in days, and equally slow offset; requires frequent monitoring for dose titration; and has multiple drug-drug and food-drug interactions. Parenteral heparin-based anticoagulants are well-studied and have more predictable pharmacokinetics but are often more expensive, only partially reversible, and require daily injections, which can be difficult for patients to tolerate over long periods of time. The NOACs are easy to administer and have predictable pharmacokinetics but are expensive, not easily reversible, and are not as extensively studied. Specific agents are preferable in some defined neurologic conditions. For acute ischemic stroke, we do not recommend immediate anticoagulation with any agent. For patients with intracranial malignancy (either primary or metastatic), we recommend a low-molecular-weight heparin (LMWH) rather than warfarin or a NOAC. For thromboembolic disease in the setting of spinal cord injury, warfarin, LMWH, or the NOACs are reasonable options. In the setting of VTE or stroke related to antiphospholipid antibody syndrome (APS), we recommend long-term warfarin anticoagulation with an INR goal of 2-3, pending the results of ongoing research involving the NOACs. For cerebral venous sinus thrombosis not related to malignancy or APS, we recommend the use of LMWH in the acute setting, followed by at least three months of warfarin. In this article, we discuss the pharmacology, pathophysiology, and comparative research that served as a basis for our recommendations.

Potential statin-drug interactions: prevalence and clinical significance

Background

Statins are cholesterol-lowering drugs widely used for cardiovascular prevention. Although safe when used alone, in combination with other drugs the likelihood of adverse drug reactions increases significantly. The exposure of the Bulgarian population to coprescriptions leading to potential statin-drug interactions is currently unknown.

Objective

The aim of this study was to investigate the incidence of coprescriptions involving statins and to compare the exposure of outpatients and inpatients to potential statin-drug interactions.

Setting

A cardiology clinic of the teaching University hospital in Varna, Bulgaria.

Method

This observational retrospective study examined the medical records of hospitalized patients prescribed a statin in combination with potentially interacting drugs. Patients who entered the hospital with a statin coprescription (considered outpatients) were compared with those coprescribed a statin at discharge from hospital (considered inpatients). Potentially interacting drugs included inhibitors and inducers of cytochrome P450 (CYP) enzymes and drugs of narrow safety margin (coumarin anticoagulants, digitalis).

Main outcome measure

The proportion of patients exposed to statin coprescriptions with potentially interacting drugs at hospital admission and discharge. Secondary outcome measures: laboratory evidence supporting possible statin-drug interactions.

Results

Out of 1641 hospitalized patients examined, 572 were prescribed a statin, either at hospital admission or discharge. Simvastatin was most commonly prescribed and simvastatin-drug coprescription predominated, especially at discharge. The exposure to all potential statin-drug interactions was similar at hospital admission (26.1%) and discharge (24.4%), as was the exposure to statin combinations with CYP inhibitors, 6.4% and 4%, correspondingly. Overall, more coprescriptions were generated, than were eliminated by hospital physicians. Amiodarone was the CYP inhibitor most frequently coprescribed. Of all interacting drugs acenocoumarol was the most commonly found, the proportions of statin-acenocoumarol coprescriptions being roughly the same at hospital entry (11.5%) and discharge (12.4%). In 7 patients out of 69 exposed to the combination, INR was found to be higher than 3, indicating a risk of over-anticoagulation.

Conclusions

Potential statin-drug interactions are common. Although they do not differ between outpatient and inpatient settings, new hazardous coprescriptions are more frequently generated in hospital. Caution is required when acenocoumarol is coprescribed with statins, especially simvastatin.

CYP2C9, VKORC1, CYP4F2, ABCB1 and F5 variants: influence on quality of long-term anticoagulation

AIMS

The study aims to evaluate the impact of genetic, demographic and clinical data on various measures of outcome of anticoagulation quality in patients.

PATIENTS AND METHODS

The study consisted of 310 patients receiving long-term oral anticoagulation therapy in our hospital. Apart from demographic and clinical variables, 21 SNPs (in 7 genes) were analyzed and compared with the outcomes of anticoagulation therapy. Various outcomes that were measured are; supra therapeutic INRs (INR >3, >6), anticoagulation stabilization, time taken to stabilize and proportion of INRs within (2-3), above (>3) and below (<2) therapeutic range.

RESULTS

Supra therapeutic INRs were influenced by CYP2C9*2, *3, CYP4F2 rs2108622, VKORC1-1639G>A, 1173C>T, rs55894764 along with concomitant drugs, smoking, body weight and height. Persistently fluctuating INRs/absolute instability correlated with VKORC1-1639G>A, gender, height and body mass index. The time taken to stabilize was associated with CYP4F2 rs2108622, CYP2C9*14, smoking, clinical indication and concomitant drugs. The overall distribution of INR was influenced by variants in CYP4F2 rs2108622, CYP2C9*3, rs9332230, VKORC1 1173C>T, -1639G>A, rs55894764, ABCB1 rs2032582, rs1128503, rs1045642 and F5 rs6025, age, smoking and concomitant drugs.

CONCLUSIONS

Knowledge of factors influencing the quality of long term anticoagulation can help clinicians to customize therapy either by dose variation, therapy with alternate choice of drug, concurrent heparin therapy and/or frequent INR monitoring.

Non-traumatic compartment syndrome secondary to deep vein thrombosis and anticoagulation

We describe an unusual case of non-traumatic compartment syndrome in three compartments of the left lower limb in a 57-year-old male inpatient. He had recently been started on anticoagulation therapy for multiple pulmonary emboli and deep vein thrombosis of the left posterior tibial and peroneal veins. Three of the four osteofascial compartments had pressures above 70 mm Hg, hence four compartment fasciotomies were performed. Postoperatively, intravenous heparin therapy was started resulting in a significant blood loss, but he had no neurovascular deficit. At reoperation, for primary wound closure, his tissues looked healthy. Non-traumatic causes of acute compartment syndrome, including deep venous thrombosis and anticoagulation, are considered.

Oral bisphosphonates do not increase the risk of severe upper gastrointestinal complications: a nested case-control study

Background

Data on the effect of oral bisphosphonates (BPs) on risk of upper gastrointestinal complications (UGIC) are conflicting. We conducted a large population-based study from a network of Italian healthcare utilization databases aimed to assess the UGIC risk associated with use of BPs in the setting of secondary prevention of osteoporotic fractures.

Methods

A nested case–control study was carried out within a cohort of 68,970 patients aged 45 years or older, who have been hospitalized for osteoporotic fracture from 2003 until 2005. Cases were the 804 patients who experienced hospitalization for UGIC until 2007. Up to 20 controls were randomly selected for each case. Conditional logistic regression model was used to estimate odds ratio (OR) associated with current and past use of BPs (i.e. for drug dispensation within 30 days and over 31 days prior the outcome onset, respectively) after adjusting for several covariates.

Results

Compared with patients who did not use BPs, current and past users had OR (and 95% confidence interval) of 0.86 (0.60 to 1.22) and 1.07 (0.80 to 1.44) respectively. There was no difference in the ORs estimated according with BPs type (alendronate or risedronate) and regimen (daily or weekly), nor with co-therapies and comorbidities.

Conclusions

Further evidence that BPs dispensed for secondary prevention of osteoporotic fractures are not associated with increased risk of severe gastrointestinal complications is supplied from this study. Further research is required to clarify the role BPs and other drugs of co-medication in inducing UGIC.

Supportive management resolved a colonic intramural hematoma in an anticoagulant user

Intramural hematomas of the colon are rare. Intramural hematomas of the gastrointestinal tract often result from blunt trauma, although they may also occur spontaneously in patients taking anticoagulants or those with blood dyscrasia. Affected patients present with abdominal pain and lower gastrointestinal bleeding, as well as occasional signs of intestinal obstruction. The diagnosis is made using colonoscopy and abdominal CT. Resection of the involved bowel segment is accepted as the standard therapy; however, experience with conservative treatment has also been reported. We herein report the case of a 62-year-old woman taking warfarin who was diagnosed with a colonic intramural hematoma and completely recovered with conservative management.

Risk of severe upper gastrointestinal complications among oral bisphosphonate users

BACKGROUND

Oral bisphosphonates (BPs) are the primary agents for the treatment of osteoporosis. Although BPs are generally well tolerated, serious gastrointestinal adverse events have been observed.

AIM

To assess the risk of severe upper gastrointestinal complications (UGIC) among BP users by means of a large study based on a network of Italian healthcare utilization databases.

METHODS

A nested case-control study was carried out by including 110,220 patients aged 45 years or older who, from 2003 until 2005, were treated with oral BPs. Cases were the 862 patients who experienced the outcome (hospitalization for UGIC) until 2007. Up to 20 controls were randomly selected for each case. Conditional logistic regression model was used to estimate odds ratio (OR) associated with current use of BPs after adjusting for several covariates. A set of sensitivity analyses was performed in order to account for sources of systematic uncertainty.

RESULTS

The adjusted OR for current use of BPs with respect to past use was 0.94 (95% CI 0.81 to 1.08). There was no evidence that this risk changed either with BP type and regimen, or concurrent use of other drugs or previous hospitalizations.

CONCLUSIONS

No evidence was found that current use of BPs increases the risk of severe upper gastrointestinal complications compared to past use.

Bleeding complications and liver injuries during phenprocoumon treatment: a multicentre prospective observational study in internal medicine departments

BACKGROUND

Even after the recent approval of newer oral anticoagulants for clinical use, the vitamin K antagonist phenprocoumon remains an important treatment option for many patients. In order to quantify the hitherto "accepted" risks of phenprocoumon treatment, we analyzed adverse drug reactions (ADRs) that led to hospitalization on the internal medicine wards of four German pharmacovigilance centers.

METHODS

We prospectively analyzed ADRs leading to hospitalization on the internal medicine wards of the hospitals belonging to the German Network of Regional Pharmacovigilance Centers (Rostock, Greifswald, Jena, and the Sophien- und Hufeland-Klinikum in Weimar) in the years 2000 to 2008.

RESULTS

The 851 patients hospitalized for a phenprocoumon-associated ADR accounted for 12.4% of the 6887 ADR-related hospitalizations in the period of the study. 723 (85%) were admitted for a hemorrhage, usually in the gastrointestinal tract (482 patients); 8 patients died as a consequence of hemorrhage associated with phenprocoumon exposure. Using drug utilization data for the catchment areas of the participating hospitals, we calculate a rate of 5 to 7 hemorrhages leading to hospitalization in an internal medicine ward per 1000 patient-years under phenprocoumon treatment. One-third of the patients who had a hemorrhage were taking other interacting drugs, mainly inhibitors of platelet aggregation and non-steroidal anti-inflammatory drugs. Among the patients who were taking phenprocoumon because of a history of thromboembolic events or for atrial fibrillation, 60% to 70% of those who had hemorrhages had an international normalized ratio (INR) that was above the upper limit of the therapeutic range. Phenprocoumon-associated impairment of liver function arose in 23 patients (2.7%).

CONCLUSION

In this study, about one-eighth of all ADR-related admissions to hospital internal medicine wards were associated with phenprocoumon. There is a need for a comparative risk-benefit assessment of phenprocoumon and the newer oral anticoagulants under real-life conditions.

Factors associated with statin selection among privately insured commercial and Medicare patients

OBJECTIVES

Given the availability of several statins in the United States, it is important to understand patient characteristics associated with their initiation. We analyzed demographic and clinical factors associated with statin selection among new statin users.

METHODS

This retrospective cohort study examined factors associated with statin selection among patients newly initiated on therapy between 1/1/2007 and 12/31/2007. Commercial and Medicare patient cohorts were evaluated separately and comparisons were made between pravastatin (PS) and other statins including simvastatin (SS), atorvastatin (AS), or rosuvastatin (RS). Multiple logistic regression models were employed to assess factors associated with PS initiation versus other statins.

RESULTS

In commercially insured patients, patients initiating PS were more likely to be older, female, and have diabetes mellitus, liver dysfunction, human immunodeficiency virus (HIV) infection, or hypertension and use calcium channel blockers, protease inhibitors, or additional lipid-modifying agents (p < 0.01 for each comparison). In Medicare-age patients, a higher percentage of PS initiators were aged 75-85, female, had atrial fibrillation, and were prescribed warfarin or triazole antifungals (p < 0.01 for each comparison). Presence of atrial fibrillation or HIV infection, or use of calcium channel blockers or additional lipid-modifying agents was associated with PS initiation compared with AS and SS. Use of warfarin was significantly associated with initiating PS compared with SS, AS, and RS in Medicare-age patients.

CONCLUSION

Older age and female gender were associated with PS initiation. In addition, selected comorbidities and use of certain medications including warfarin or protease inhibitors were associated with PS initiation, which may reflect the tolerability of PS and its reduced risk of significant drug-drug interactions for certain patients. Because this study is a retrospective analysis of US healthcare claims, the findings are limited to only those factors captured within claims data and may not be generalizable to all patient populations in which statin therapy is initiated.

A review of time courses and predictors of lipid changes with fenofibric acid-statin combination

Fibrates activate peroxisome proliferator activated receptor α and exert beneficial effects on triglycerides, high-density lipoprotein cholesterol, and low density lipoprotein subspecies. Fenofibric acid (FA) has been studied in a large number of patients with mixed dyslipidemia, combined with a low- or moderate-dose statin. The combination of FA with simvastatin, atorvastatin and rosuvastatin resulted in greater improvement of the overall lipid profile compared with the corresponding statin dose. The long-term efficacy of FA combined with low- or moderate- dose statin has been demonstrated in a wide range of patients, including patients with type 2 diabetes mellitus, metabolic syndrome, or elderly subjects. The FA and statin combination seems to be a reasonable option to further reduce cardiovascular risk in high-risk populations, although trials examining cardiovascular disease events are missing.

A clinically significant interaction between warfarin and simvastatin is unique to carriers of the CYP2C9*3 allele

Background: Simvastatin interacts with warfarin, but the strength of the interaction varies between individual patients, indicating a genetic predisposition. Patients & methods: The influence of the CYP2C9*2 and CYP2C9*3 polymorphisms on the interaction between simvastatin and warfarin was analyzed in data from 1132 patients. Results: Simvastatin use reduced warfarin dose requirements by 29% in carriers of the CYP2C9*3 allele, compared with 5% in noncarriers. A regression model showed a significant influence of CYP2C9*3 on the drug–drug interaction, predicting a warfarin dose reduction of 25% in CYP2C9*3 heterozygotes and 43% in CYP2C9*3 homozygotes. Conclusion: Our data indicate that the CYP2C9*3 polymorphism predisposes for a pharmacologic interaction between warfarin and simvastatin.

Original submitted 5 January 2012; Revision submitted 15 February 2012