Multiple outcomes associated with the use of metformin and sulphonylureas in type 2 diabetes: a population-based cohort study in Italy

Metformin Use and Clinical Outcomes Among Patients With Diabetes Mellitus With or Without Heart Failure or Kidney Dysfunction

Background:

Metformin is first-line therapy for type 2 diabetes mellitus, although its effects on the cardiovascular system are unproved.

Methods:

In this post hoc analysis, patients in SAVOR-TIMI 53 (Saxagliptin and Cardiovascular Outcomes in Patients With Type 2 Diabetes Mellitus) with baseline biomarker samples (n=12 156) were classified as ever versus never taking metformin during the trial period. Associations between metformin exposure and outcomes were estimated with inverse probability of treatment weighting Cox modeling for the composite end point of cardiovascular death, myocardial infarction, or ischemic stroke, as well as cardiovascular death and all-cause mortality, with biomarkers included as covariates. Additional sensitivity analyses included propensity score matching and Cox multivariable models.

Results:

Of the 12 156 patients with baseline biomarker samples, 8971 (74%) had metformin exposure, 1611 (13%) had prior heart failure, and 1332 (11%) had at least moderate chronic kidney disease (estimated glomerular filtration rate ≤45 mL·min −1 ·1.73 m −2 ). Metformin use was associated with no difference in risk for the composite end point (hazard ratio for inverse probability of treatment weighting, 0.92 [95% CI, 0.76–1.11]) but lower risk of all-cause mortality (hazard ratio for inverse probability of treatment weighting, 0.75 [95% CI, 0.59–0.95]). There was no significant relationship between metformin use and these end points in patients with prior heart failure or moderate to severe chronic kidney disease.

Conclusions:

In a cohort of 12 156 patients with type 2 diabetes mellitus and high cardiovascular risk, metformin use was associated with lower rates of all-cause mortality, including after adjustment for clinical variables and biomarkers, but not lower rates of the composite end point of cardiovascular death, myocardial infarction, or ischemic stroke. This association was most apparent in patients without prior heart failure or moderate to severe chronic kidney disease.

Clinical Trial Registration:

URL: https://www.clinicaltrials.gov . Unique identifier: NCT01107886.

Building reliable evidence from real-world data: Needs, methods, cautiousness and recommendations

National healthcare systems of advanced countries, including Italy, widely agree on the approach whereby public healthcare decisions should be driven by available evidence on effectiveness and safety of therapeutics. It is equally accepted that randomized controlled clinical trials (RCTs), although universally recognised as the most robust "evidence generators", are insufficient for guiding the decision-making process since they are intrinsically unsuited to capture the impact of treatments in routine clinical practice. The complexity of treatments, as well as the demographic and clinical heterogeneity of patients receiving the treatments, and the long period of many treatments, explain the gap between the evidence generated in the controlled, but artificial, setting of RCTs and their current impact in the real world. The so-called pragmatic RCTs, despite guaranteeing greater flexibility compared to conventional trials, are not always able to reduce this gap. This explains the growing interest in the development of methods able to produce evidence on the real-world impact of care pathways (i.e., real-world evidence). Among them, those based on the Electronic Healthcare Records (EHRs), as the databases on the healthcare services of the National Health System provided to beneficiaries, known as Healthcare Utilization Databases (HCU), are becoming established and receiving increasing attention from the scientific community and healthcare decision-makers. We described the research areas in which HCU databases may be particularly useful, jointly with strength, weakness and potential of this approach. It is concluded that HCU data cannot substitute RCTs but they can usefully complement RCT data for adequately supporting healthcare decision-makers.

Sulfonylureas and the Risks of Cardiovascular Events and Death: A Methodological Meta-Regression Analysis of the Observational Studies

Recent randomized trials have compared the newer antidiabetic agents to treatments involving sulfonylureas, drugs associated with increased cardiovascular risks and mortality in some observational studies with conflicting results. We reviewed the methodology of these observational studies by searching MEDLINE from inception to December 2015 for all studies of the association between sulfonylureas and cardiovascular events or mortality. Each study was appraised with respect to the comparator, the outcome, and study design-related sources of bias. A meta-regression analysis was used to evaluate heterogeneity. A total of 19 studies were identified, of which six had no major design-related biases. Sulfonylureas were associated with an increased risk of cardiovascular events and mortality in five of these studies (relative risks 1.16-1.55). Overall, the 19 studies resulted in 36 relative risks as some studies assessed multiple outcomes or comparators. Of the 36 analyses, metformin was the comparator in 27 (75%) and death was the outcome in 24 (67%). The relative risk was higher by 13% when the comparator was metformin, by 20% when death was the outcome, and by 7% when the studies had design-related biases. The lowest predicted relative risk was for studies with no major bias, comparator other than metformin, and cardiovascular outcome (1.06 [95% CI 0.92-1.23]), whereas the highest was for studies with bias, metformin comparator, and mortality outcome (1.53 [95% CI 1.43-1.65]). In summary, sulfonylureas were associated with an increased risk of cardiovascular events and mortality in the majority of studies with no major design-related biases. Among studies with important biases, the association varied significantly with respect to the comparator, the outcome, and the type of bias. With the introduction of new antidiabetic drugs, the use of appropriate design and analytical tools will provide their more accurate cardiovascular safety assessment in the real-world setting.

Therapeutic molecules against type 2 diabetes: What we have and what are we expecting?

World Health Organization (WHO) has identified diabetes as one of the fastest growing non-communicable diseases with 422 million patients around the world in 2014. Diabetes, a metabolic disease, is characterized primarily by hyperglycemia which results in various macrovascular and microvascular complications like cardiovascular disease and neuropathies which can significantly deteriorate the quality of life. The body either does not manufactures enough insulin (type 1 diabetes or T1DM) or becomes insensitive to physiologically secreted insulin or both (type 2 diabetes or T2DM). The majority of the diabetic population is affected by type 2 diabetes. Currently, hyperglycemia is treated by a broad range of molecules such as biguanides, sulfonylurea, insulin, thiazolidinediones, incretin mimetics, and DPP-4 inhibitors exerting different mechanisms. However, new drug classes have indeed come in the market such as SGLT-2 inhibitors and other are in the experimental stages such as GPR 40 agonists, GSK-3 inhibitors, GK activators and GPR21 inhibitors which definitely could be anticipated as safe and effective for diabetes therapy. This article reviews the general approach to currently approved therapies for type 2 diabetes and focusing on novel approaches that could be a panacea and might be useful in the future for diabetes patients.

Comparative risk of major cardiovascular events associated with second-line antidiabetic treatments: a retrospective cohort study using UK primary care data linked to hospitalization and mortality records

AIMS

To examine the risk of major cardiovascular events associated with second-line diabetes therapies, in patients with type 2 diabetes, after adjusting for known cardiovascular risk factors.

METHODS

This was a retrospective cohort study of patients prescribed second-line regimens between 1998 and 2011 after first-line metformin. The UK Clinical Practice Research Datalink, with linked national hospitalization and mortality data, for the period up to December 2013, was used. Inverse probability of treatment-weighted time-varying Cox regression models was used to estimate hazard ratios (HRs) and 95% confidence intervals (CIs) for developing a major cardiovascular event (cardiovascular death, myocardial infarction, stroke, acute coronary syndrome, unstable angina, or coronary revascularization) associated with second-line therapies. Analyses adjusted for patient demographic characteristics, comorbidities, glycated haemoglobin, socio-economic status, ethnicity, smoking status and concurrent medications.

RESULTS

A total of 10 118 initiators of a second-line add-on to metformin of either a sulphonylurea (n = 6740), dipeptidyl peptidase-4 (DPP-4) inhibitor (n = 1030) or thiazolidinedione (n = 2348) were identified. After a mean (standard deviation) of 2.4 (1.9) years of follow-up, 386, 36 and 95 major cardiovascular events occurred in sulphonylurea-, DPP-4 inhibitor- and thiazolidinedione-initiators, respectively. In comparison with the metformin-sulphonylurea regimen, adjusted HRs were 0.78 (95% CI 0.55; 1.11) for the metformin-DPP-4 inhibitor regimen and 0.68 (95% CI 0.54; 0.85) for the metformin-thiazolidinedione regimen.

CONCLUSIONS

Thiazolidinedione add-on treatments to metformin were associated with lower risks of major cardiovascular disease or cardiovascular death compared with sulphonylurea add-on treatment to metformin. Lower, but non-statistically significant, risks were also found with DPP-4 inhibitor add-on therapies.

Use of cystatin C to inform metformin eligibility among adult veterans with diabetes

AIMS

Recommendations for metformin use are dependent on eGFR category: eGFR >45 ml/min/1.73 m2 - "first-line agent"; eGFR 30-44 - "use with caution"; eGFR<30 - "do not use". Misclassification of metformin eligibility by creatinine-based MDRD GFR estimates (eGFRcr) may contribute to its misuse. We investigated the impact of cystatin c estimates of GFR (eGFRcys) on metformin eligibility.

METHODS

In a consecutive cohort of 550 Veterans with diabetes, metformin use and eligibility were assessed by eGFR category, using eGFRcr and eGFRcys. Discrepancy in eligibility was defined as cases where eGFRcr and eGFRcys categories (<30, 30-44, 45-60, and >60 ml/min/1.73 m2) differed with an absolute difference in eGFR of >5 ml/min/1.73 m2. We modeled predictors of metformin use and eGFR category discrepancy with multivariable relative risk regression and multinomial logistic regression.

RESULTS

Subjects were 95% male, median age 68, and racially diverse (45% White, 22% Black, 11% Asian, 22% unknown). Metformin use decreased with severity of eGFRcr category, from 63% in eGFRcr >60 to 3% in eGFRcr <30. eGFRcys reclassified 20% of Veterans into different eGFR categories. Factors associated with a more severe eGFRcys category compared to eGFRcr were older age (aOR = 2.21 per decade, 1.44-1.82), higher BMI (aOR = 1.04 per kg/m2, 1.01-1.08) and albuminuria >30 mg/g (aOR = 1.81, 1.20-2.73).

CONCLUSIONS

Metformin use is low among Veterans with CKD. eGFRcys may serve as a confirmatory estimate of kidney function to allow safe use of metformin among patients with CKD, particularly among older individuals and those with albuminuria.

Trastuzumab for HER2+ metastatic breast cancer in clinical practice: Cardiotoxicity and overall survival

The evidence on efficacy and safety of trastuzumab in metastatic breast cancers (MBC) mainly derives from randomized clinical trials. We assessed short- and long-term overall survival (OS) and cardiotoxicity in a large cohort of women with MBC treated with trastuzumab in clinical settings. Using healthcare administrative data of Lombardy (10 millions inhabitants), we identified a cohort of women receiving trastuzumab for MBC between 2006 and 2009. The cumulative risk of severe cardiac events and the OS from the first trastuzumab administration were estimated using the Kaplan-Meier method. Their predictors were assessed using Cox regression models. We found 681 trastuzumab MBC users. Thirty two (4.7%) women experienced severe cardiac adverse events. The cumulative risk increased sharply, reaching a value of 2.4% and 4.3% during the first and second year; thereafter it increased of about 1% per year. Age was a strong predictor of cardiotoxicity. The OS was 81.8%, 64.0%, 50.2%, 41.1% and 37.2% at 1, 2, 3, 4 and 5 years, respectively. Independent predictors of worse OS were: age, brain liver or lung metastasis compared to other metastasis, use of taxanes and other chemotherapies, a cardiac adverse event after trastuzumab use, and a higher time between metastasis and BC diagnoses. The incidence of cardiotoxicity among women treated with trastuzumab for HER2-positive MBC appeared higher than that reported in RCTs, particularly in elder patients. In spite of this, median survival, was, if anything, better.

Cardiovascular safety of sulphonylureas: over 40 years of continuous controversy without an answer

More than 40 years after publication of the University Group Diabetes Program trial, the cardiovascular safety of sulphonylureas is still contentious. Although several hypotheses linking sulphonylureas to adverse cardiovascular effects exist, none provide conclusive evidence. Adding to the controversy, current clinical trials and observational studies provide inconsistent, and sometimes conflicting, evidence for the cardiovascular effects of sulphonylureas. Overall, observational evidence suggests that an increased risk of adverse cardiovascular outcomes is associated with sulphonylureas; however, these data may be subject to residual confounding and bias. Although evidence from randomized controlled trials has suggested a neutral effect, the majority of these studies were not specifically designed to assess the effect of sulphonylureas on adverse cardiovascular event risk. Current ongoing large clinical trials may provide some clarity on the cardiovascular safety of sulphonylureas, but the results are not expected for several years. With the continued uncertainties concerning the cardiovascular safety of all antidiabetic drugs, a clear answer with regard to sulphonylureas is warranted. The objectives of the present article were to provide an overview of the controversy surrounding sulphonylurea-related cardiovascular effects, to discuss the limitations of the current literature, and to provide recommendations for future studies aiming to elucidate the true relationship between sulphonylureas and adverse cardiovascular effects in people with type 2 diabetes.

Capitalizing on prescribing pattern variation to compare medications for type 2 diabetes

BACKGROUND

Clinical trials often compare hypoglycemic medications on the basis of glycemic control but do not examine long-term outcomes (e.g., mortality). This study demonstrates an alternative approach to lengthening clinical trials to assess these long-term outcomes.

OBJECTIVE

To use observational quasi-experimental methods using instrumental variables (IVs) to compare the effect of two hypoglycemic medications, sulfonylureas (SUs) and thiazolidinediones (TZDs), on long-term outcomes.

METHODS

This study used administrative data from the Veterans Health Administration and Medicare from 2000 to 2010. The study population included US veterans dually enrolled in Medicare who received a prescription for metformin and then initiated SUs or TZDs. Patients could either continue on or discontinue metformin after the initiation of the second agent. Treatment was defined as starting either a SU or a TZD. Local variations in SU prescribing rates were used as instruments in IV models to control for selection bias. Survival models predicted all-cause mortality, ambulatory care sensitive condition hospitalizations, and stroke or heart attack (acute myocardial infarction).

RESULTS

Starting on SUs compared to TZDs significantly increased the likelihood of experiencing mortality and ACSC hospitalization. The estimated hazard ratio for the effect of starting on SUs compared to TZDs was 1.50 (95% confidence interval [CI] 1.09-2.09) for all-cause mortality, 1.68 (95% CI 1.31-2.15) for ambulatory care sensitive condition hospitalization, and 1.15 (95% CI 0.80-1.66) for acute myocardial infarction or stroke.

CONCLUSIONS

Our findings suggest increased risk of major adverse events associated with SUs as a second-line agent. Quasi-experimental IV methods may be an important alternative to lengthening clinical trials to assess long-term outcomes.

Observational studies of the association between glucose-lowering medications and cardiovascular outcomes: addressing methodological limitations

BACKGROUND

Recent years have witnessed a growing body of observational literature on the association between glucose-lowering treatments and cardiovascular disease. However, many of the studies are based on designs or analyses that inadequately address the methodological challenges involved.

METHODS

We reviewed recent observational literature on the association between glucose-lowering medications and cardiovascular outcomes and assessed the design and analysis methods used, with a focus on their ability to address specific methodological challenges. We describe and illustrate these methodological issues and their impact on observed associations, providing examples from the reviewed literature. We suggest approaches that may be employed to manage these methodological challenges.

RESULTS

From the evaluation of 81 publications of observational investigations assessing the association between glucose-lowering treatments and cardiovascular outcomes, we identified the following methodological challenges: 1) handling of temporality in administrative databases; 2) handling of risks that vary with time and treatment duration; 3) definitions of the exposure risk window; 4) handling of exposures that change over time; and 5) handling of confounding by indication. Most of these methodological challenges may be suitably addressed through application of appropriate methods.

CONCLUSIONS/INTERPRETATION

Observational research plays an increasingly important role in the evaluation of the clinical effects of diabetes treatment. Implementation of appropriate research methods holds the promise of reducing the potential for spurious findings and the risk that the spurious findings will mislead the medical community about risks and benefits of diabetes medications.

Sulfonylurea use and incident cardiovascular disease among patients with type 2 diabetes: prospective cohort study among women

OBJECTIVE

Evidence is inconsistent for the association between sulfonylurea use and risk of cardiovascular disease among patients with diabetes. We aimed to prospectively evaluate this association using the Nurses' Health Study (NHS), a well-established cohort of U.S. women with long-term follow-up.

RESEARCH DESIGN AND METHODS

We followed 4,902 women (mean age 68 years) with diabetes (mean duration 11 years), but without cardiovascular disease at baseline. The use of sulfonylureas and other medications was self-reported at baseline and during the follow-up period of up to 10 years. Cox proportional hazards regression models were used to estimate the relative risk (RR) and 95% CI for the association between the sulfonylurea use and incident cardiovascular disease while accounting for potential confounders, including age, diabetes duration, diabetes-related complications, other antihyperglycemic medications, BMI, lifestyle factors, family history of cardiovascular diseases, and present chronic conditions. We also applied the propensity score stratification method to address the possibility of residual confounding.

RESULTS

We identified 339 incident cases of cardiovascular disease, including 191 cases of coronary heart disease (CHD) and 148 cases of stroke. A longer duration of sulfonylurea use was significantly associated with a higher risk of CHD (P for trend = 0.002); the RRs for CHD were 1.24 (95% CI 0.85-1.81) for patients who used sulfonylurea therapy for 1-5 years, 1.51 (0.94-2.42) for 6-10 years, and 2.15 (1.31-3.54) for >10 years, compared with nonusers. Compared with users of metformin monotherapy, the RR for CHD was 3.27 (1.31-8.17) for those who were treated with the combination of metformin and sulfonylurea. The analysis using propensity score stratification yielded similar results. We did not observe a significant association between sulfonylurea therapy and stroke risk.

CONCLUSIONS

Long-term use of sulfonylureas was associated with a significantly higher risk of developing CHD among women with diabetes.

Risk of acute coronary events associated with glyburide compared with gliclazide use in patients with type 2 diabetes: a nested case-control study

AIM

Sulfonylureas might increase the risk of adverse cardiovascular events; however, emerging evidence suggests there may be important differences amongst these drugs. Some, like glyburide, inhibit KATP channels in the heart and pancreas, while others, like gliclazide, are more likely to selectively inhibit KATP channels in the pancreas. We hypothesized that the risk of acute coronary syndrome (ACS) events would be higher in patients using glyburide compared with gliclazide.

METHODS

This nested case-control study used administrative health data from Alberta, Canada. New users of glyburide or gliclazide aged ≥66 years between 1998 and 2010 were included. Cases were individuals with an ACS-related hospitalization or death. Up to four controls were matched based on birth year, sex, cohort-entry year and follow-up time. Multivariable conditional logistic regression was used to estimate adjusted odds ratios (OR), controlling for baseline drug use and co-morbidities.

RESULTS

Our cohort included 7441 gliclazide and 13 884 glyburide users; 51.4% men, mean (s.d.) age 75.5 (6.6) years and mean (s.d.) duration of follow-up 5.5 (4.0) years. A total of 4239 patients had an ACS-related hospitalization or death and were matched to 16 723 controls. Compared with gliclazide use, glyburide use was associated with a higher risk (adjusted OR 1.14; 95% CI 1.06-1.23) of ACS-related hospitalization or death over 5.5 years (number needed to harm: 50).

CONCLUSION

In this observational study, glyburide use was associated with a 14% higher risk of ACS events compared with gliclazide use. Although the difference is small and probably to have implications at the population level rather than the individual patient or clinician, any causal inferences regarding sulfonylurea use and adverse cardiovascular risk should be tested in a large-scale randomized controlled trial.

Trastuzumab-related cardiotoxicity in early breast cancer: a cohort study

BACKGROUND

Concerns have been raised about the cardiac safety profile of trastuzumab for the adjuvant treatment of early stage breast cancer in clinical practice. We assessed trastuzumab-related cardiotoxicity and its predictors in a large cohort of Italian women.

METHODS

Through a record linkage between four regional health care databases, we identified the rate of severe cardiac adverse events among women treated with trastuzumab for early breast cancer in Lombardy. The cumulative risk of cardiotoxicity was estimated using the Kaplan-Meier method, and independent predictors were assessed using the Cox model.

RESULTS

Of 2,046 trastuzumab users, 53 (2.6%) experienced at least one hospitalization for a cardiac event, and there were two cardiac deaths. The cumulative risk of cardiotoxicity increased up to 2 years after starting treatment, reaching a plateau at 2.8%. The risk was low (0.2%) among young women, whereas the incidence was approximately 10% in women aged ≥70 years, irrespective of cardiovascular risk factors. Age and history of cardiac disease were strong predictors of cardiotoxicity, with a hazard ratio of 11.3 (95% confidence interval [CI]: 3.5-36.6) for women aged ≥70 years as compared with those <50 years of age. Hazard ratio was 4.4 (95% CI: 2.1-9.5) for women with a history of cardiac disease compared with those without a history of cardiac disease.

CONCLUSIONS

Cardiotoxicity of trastuzumab varies considerably across subgroups of patients. The long-term safety profile was less favorable than in the largest clinical trial. Strategies to reduce cardiotoxicity in high-risk women should be investigated.

Mortality outcomes of different sulphonylurea drugs: the results of a 14-year cohort study of type 2 diabetic patients

OBJECTIVE

Available data about mortality of type 2 diabetic patients treated with different sulphonylureas are scarce and contradictory.

DESIGN

We evaluated the associations between all-cause and cause-specific mortality and treatments with different sulphonylureas in a retrospective cohort of type 2 diabetic patients from a diabetes clinic.

METHODS

All 1277 patients treated with sulphonylureas during 19961997 were enrolled: 159 patients were treated with tolbutamide, 977 glibenclamide and 141 gliclazide. The baseline data (centralised laboratory parameters, anthropometric data and presence of chronic complications) were abstracted from the clinical records. Information on vital status was collected from demographic files after 14-year follow-up. Adjusted hazard ratios (HR) were estimated with Cox (all-cause mortality) or Fine and Gray models (cause-specific mortality), including several potential confounders.

RESULTS

Five hundred and fifty-six patients died during the follow-up: 262 from cardiovascular causes, 158 from cancer and 136 from other causes. When compared with the glibenclamide users, the gliclazide and tolbutamide users showed a significantly lower cancer mortality (HR=0.30; 95% CI 0.16-0.55, and HR=0.48; 95% CI 0.29-0.79 respectively). These results were strongly confirmed in the 555 patients on sulphonylurea monotherapy. None of the patients who were treated with gliclazide monotherapy died from cancer during the follow-up, and the patients on tolbutamide treatment exhibited a lower cancer mortality than the glibenclamide users (HR=0.40; 95% CI 0.22-0.71). Data did not change after stratification for the duration of sulphonylurea treatment from diabetes diagnosis to the study enrollment.

CONCLUSIONS

Cancer mortality was markedly reduced in the patients on gliclazide and tolbutamide treatment. These results suggest additional benefits for these drugs beyond their blood glucose-lowering effect and strongly advocate for further investigation.

Association of sulphonylurea treatment with all-cause and cardiovascular mortality: a systematic review and meta-analysis of observational studies

We conducted a meta-analysis of cohort and case-control studies to evaluate all-cause and cardiovascular (CV) mortality of patients with type 2 diabetes mellitus (T2DM) who received sulphonylurea (SU) treatment, when compared to any other diabetes treatment. Only studies reporting raw data on mortality during SU treatment were included. Data were combined using random-effects (RE) models. Unadjusted odds ratios (ORs) are presented. Of 4991 publication titles and abstracts reviewed, 20 studies (n = 551,912 patients) were included. For cohort studies (n = 276,050), patients receiving SU monotherapy or combination treatment had significantly higher all-cause and CV mortality risks compared to any non-SU treatment [all-cause, 13 studies: OR = 1.92, 95% confidence interval (CI) = 1.48-2.49; CV, 5 studies: OR = 2.72, 95% CI = 1.95-3.79]. Validity was limited by the high treatment group heterogeneity (I (2) > 90%) and study-inherent biases/design differences. In conclusion, patients receiving SU treatment had increased all-cause and CV mortality risks. However, the meta-analysis was limited by the high heterogeneity of non-randomized studies.

Comparative effectiveness of sulfonylurea and metformin monotherapy on cardiovascular events in type 2 diabetes mellitus: a cohort study

BACKGROUND

The effects of sulfonylureas and metformin on outcomes of cardiovascular disease (CVD) in type 2 diabetes are not well-characterized.

OBJECTIVE

To compare the effects of sulfonylureas and metformin on CVD outcomes (acute myocardial infarction and stroke) or death.

DESIGN

Retrospective cohort study.

SETTING

National Veterans Health Administration databases linked to Medicare files.

PATIENTS

Veterans who initiated metformin or sulfonylurea therapy for diabetes. Patients with chronic kidney disease or serious medical illness were excluded.

MEASUREMENTS

Composite outcome of hospitalization for acute myocardial infarction or stroke, or death, adjusted for baseline demographic characteristics; medications; cholesterol, hemoglobin A1c, and serum creatinine levels; blood pressure; body mass index; health care utilization; and comorbid conditions.

RESULTS

Among 253 690 patients initiating treatment (98 665 with sulfonylurea therapy and 155 025 with metformin therapy), crude rates of the composite outcome were 18.2 per 1000 person-years in sulfonylurea users and 10.4 per 1000 person-years in metformin users (adjusted incidence rate difference, 2.2 [95% CI, 1.4 to 3.0] more CVD events with sulfonylureas per 1000 person-years; adjusted hazard ratio [aHR], 1.21 [CI, 1.13 to 1.30]). Results were consistent for both glyburide (aHR, 1.26 [CI, 1.16 to 1.37]) and glipizide (aHR, 1.15 [CI, 1.06 to 1.26]) in subgroups by CVD history, age, body mass index, and albuminuria; in a propensity score-matched cohort analysis; and in sensitivity analyses.

LIMITATION

Most of the veterans in the study population were white men; data on women and minority groups were limited but reflective of the Veterans Health Administration population.

CONCLUSION

Use of sulfonylureas compared with metformin for initial treatment of diabetes was associated with an increased hazard of CVD events or death.

PRIMARY FUNDING SOURCE

Agency for Healthcare Research and Quality and the U.S. Department of Health and Human Services.

Electronic healthcare databases for active drug safety surveillance: is there enough leverage?

PURPOSE

To provide estimates of the number and types of drugs that can be monitored for safety surveillance using electronic healthcare databases.

METHODS

Using data from eight European databases (administrative claims, medical records) and in the context of a cohort study, we determined the amount of drug exposure required for signal detection across varying magnitudes of relative risk (RR). We provide estimates of the number and types of drugs that can be monitored as a function of actual use, minimal detectable RR, and empirically derived incidence rates for the following adverse events: (i) acute myocardial infarction; (ii) acute renal failure; (iii) anaphylactic shock; (iv) bullous eruptions; (v) rhabdomyolysis; and (vi) upper gastrointestinal bleeding. We performed data simulation to see how expansion of database size would influence the capabilities of such system.

RESULTS

Data from 1,947,452 individuals (59,594,132 person-years follow-up) who used 2,289 drugs in the EU-ADR network show that for a frequent event such as acute myocardial infarction, there are 531 drugs (23% of total) for which an association with RR = 2, if present, can be investigated. For a rare event such as rhabdomyolysis, there are 19 drugs (1%) for which an association of same magnitude can be investigated.

CONCLUSION

Active surveillance using healthcare data-based networks for signal detection is feasible, although the leverage to do so may be low for infrequently used drugs and for rare outcomes. Extending database network size to include data from heterogeneous populations and increasing follow-up time are warranted to maximize leverage of these surveillance systems.

Comparisons of persistence and durability among three oral antidiabetic therapies using electronic prescription-fill data: the impact of adherence requirements and stockpiling

Two important challenges are inherent in the design of studies using prescription data from electronic health records: how to define the minimum level of adherence that would qualify as "continuous drug use" and how to handle stockpiling of medications. Generally, the sensitivity of a study's conclusions to these design choices is not analyzed. In our study, covariate adjusted Cox models were used to compare persistence and durability with respect to three common oral antidiabetic therapies in a cohort of 12,697 incident users. Assuming 50% stockpiling, sulfonylurea therapy, as compared with metformin, showed a significantly lower risk of nonpersistence (changing or stopping therapy) when no gap days were allowed (HR 0.95, P = 0.032), no significant difference when 14 gap days were allowed (HR 0.99, P = 0.536), and significantly greater risk of nonpersistence when 30 gap days were allowed (HR 1.05, P = 0.046). All the drug comparisons showed statistically significant effects in both directions, the risk of nonpersistence increasing or decreasing depending on the design parameters.