PURPOSE: To replicate the well-established association between angiotensin-converting enzyme inhibitors versus beta blockers and angioedema in the International Classification of Diseases, 10th Revision, Clinical Modification (ICD-10-CM) era.
METHODS: We conducted a retrospective, inception cohort study in a large insurance database formatted to the Sentinel Common Data Model. We defined study periods spanning the ICD-9-CM era only, ICD-10-CM era only, and ICD-9-CM and ICD-10-CM era and conducted simple-forward mapping (SFM), simple-backward mapping (SBM), and forward-backward mapping (FBM) referencing the General Equivalence Mappings to translate the outcome (angioedema) and covariates from ICD-9-CM to ICD-10-CM. We performed propensity score (PS)-matched and PS-stratified Cox proportional hazards regression to estimate hazard ratios (HRs) and 95% confidence intervals (CIs).
RESULTS: In the ICD-9-CM and ICD-10-CM eras spanning April 1 to September 30 of 2015 and 2016, there were 152 017 and 145 232 angiotensin-converting enzyme inhibitor initiators and 115 073 and 116 652 beta-blocker initiators, respectively. The PS-matched HR was 4.19 (95% CI, 2.82-6.23) in the ICD-9-CM era, 4.37 (2.92-6.52) in the ICD-10-CM era using SFM, and 4.64 (3.05-7.07) in the ICD-10-CM era using SBM and FBM. The PS-matched HRs from the mixed ICD-9-CM and ICD-10-CM eras ranged from 3.91 (2.69-5.68) to 4.35 (3.33-5.70).
CONCLUSION: The adjusted HRs across different diagnostic coding eras and the use of SFM versus SBM and FBM produced numerically different but clinically similar results. Additional investigations as ICD-10-CM data accumulate are warranted.
AIM: We examined characteristics of early sacubitril/valsartan users in a large US electronic health records database.
PATIENTS & METHODS: We identified three cohorts of patients with heart failure (HF): sacubitril/valsartan patients with a prior HF diagnosis; patients with HF with reduced ejection fraction; and patients with HF treated with an angiotensin-converting enzyme inhibitor or angiotensin II receptor blocker and a β-blocker.
RESULTS: Sacubitril/valsartan patients were younger than patients in the other cohorts; the mean age of sacubitril/valsartan patients increased by 2 years in the first 15 months of marketing. Most sacubitril/valsartan patients had prior use of HF treatment.
CONCLUSION: Overall, sacubitril/valsartan patients resembled those in the HF with reduced ejection fraction cohort, and commonly used other drugs for HF.
PURPOSE: Comparative outcomes of treatment with antiplatelet drugs in patients with acute coronary syndrome (ACS) and co-morbid diabetes mellitus (DM) are not well studied.
METHODS: We performed a cohort study using US commercial claims data (2009-2015) and conducted the following pairwise comparisons in ACS patients with DM: prasugrel vs clopidogrel, ticagrelor vs clopidogrel, and prasugrel vs ticagrelor. Outcomes of interest included (1) a composite effectiveness endpoint including myocardial infarction, ischemic stroke, or inpatient mortality; (2) a composite safety endpoint including major bleeding events requiring hospitalization; and (3) pneumonia hospitalizations as a negative control endpoint. We used calendar time-specific propensity score matching to account for confounding and applied Cox proportional hazard models to calculate hazard ratios (HR) with 95% confidence intervals (CI).
RESULTS: Comparative risk of the effectiveness endpoint was lower among prasugrel initiators compared to clopidogrel initiators (HR 0.82, 95% CI 0.68-0.99, N = 7011 matched pairs), but no different between ticagrelor and clopidogrel (HR 1.02, 95% CI 0.76-1.37, N = 3013 pairs) or prasugrel and ticagrelor (HR 0.83, 95% CI 0.58-1.18, N = 2207 pairs). Bleeding risk was higher among prasugrel initiators when compared to clopidogrel initiators within the first month of treatment (HR 1.85, 95% CI 1.03-3.35); no other comparison indicated any difference. No differences in the negative control outcomes were noted after PS matching for all comparisons, indicating adequate confounding control.
CONCLUSIONS: Prasugrel was associated with superior cardiovascular outcomes and a higher risk of short-term bleeding compared to clopidogrel in patients with ACS and DM. Comparative outcomes were similar between ticagrelor and clopidogrel or prasugrel and ticagrelor.
OBJECTIVE: To examine the association between individual antidiabetic sulfonylureas and outpatient-originating sudden cardiac arrest and ventricular arrhythmia (SCA/VA).
RESEARCH DESIGN AND METHODS: We conducted a retrospective cohort study using 1999-2010 U.S. Medicaid claims from five large states. Exposures were determined by incident use of glyburide, glimepiride, or glipizide. Glipizide served as the reference exposure, as its effects are believed to be highly pancreas specific. Outcomes were ascertained by a validated ICD-9-based algorithm indicative of SCA/VA (positive predictive value ∼85%). Potential confounding was addressed by adjustment for multinomial high-dimensional propensity scores included as continuous variables in a Cox proportional hazards model.
RESULTS: Of sulfonylurea users under study ( = 519,272), 60.3% were female and 34.9% non-Hispanic Caucasian, and the median age was 58.0 years. In 176,889 person-years of sulfonylurea exposure, we identified 632 SCA/VA events (50.5% were immediately fatal) for a crude incidence rate of 3.6 per 1,000 person-years. Compared with glipizide, propensity score-adjusted hazard ratios for SCA/VA were 0.82 (95% CI 0.69-0.98) for glyburide and 1.10 (0.89-1.36) for glimepiride. Numerous secondary analyses showed a very similar effect estimate for glyburide; yet, not all CIs excluded the null.
CONCLUSIONS: Glyburide may be associated with a lower risk of SCA/VA than glipizide, consistent with a very small clinical trial suggesting that glyburide may reduce ventricular tachycardia and isolated ventricular premature complexes. This potential benefit must be contextualized by considering putative effects of different sulfonylureas on other cardiovascular end points, cerebrovascular end points, all-cause death, and hypoglycemia.
BACKGROUND: Direct oral anticoagulants (DOACs) have been proposed as a more convenient alternative to vitamin K antagonists (VKAs), which are commonly associated with poor treatment persistence in non-valvular atrial fibrillation (nv-AF).
METHODS: Using data from the French national health care databases (Régime Général, 50 million beneficiaries), a cohort study was conducted to compare the 1-year non-persistence rates in nv-AF patients initiating dabigatran (N=11,141) or rivaroxaban (N=11,126) versus VKA (N=11,998). Treatment discontinuation was defined as a switch between oral anticoagulant (OAC) classes or a 60-day gap with no medication coverage, with the additional criterion of no reimbursement for international normalized ratio monitoring during this gap for VKA patients. Considering death as a competing risk, differences between 1-year discontinuation rates were used to compare each DOAC versus VKA. The 95% confidence intervals (CIs) were estimated via bootstrapping. Baseline patient characteristics were adjusted using inverse probability of treatment weighting. Subgroup analyses considered DOAC dose at initiation, age, risk of stroke, and bleeding.
RESULTS: Adjusted 1-year discontinuation rates were higher for dabigatran than for VKA new users (36.8% vs 30.2%; difference: 6.6% [95% CI, 5.5-7.6]) and for rivaroxaban versus VKA new users (33.4% vs 30.4%; 3.0% [1.9-4.1]). Similar differences were found in all subgroup analyses, except in dabigatran and rivaroxaban patients <75 years (dabigatran vs VKA: 0.3% [-1.4 to 1.8]; rivaroxaban vs VKA: -2.6% [-4.3 to -0.9]) and dabigatran 150 mg new users (-1.1% [-3.1 to 0.7]). Consistent results were obtained when considering both switches between OAC classes and death as competing risks of treatment discontinuation.
CONCLUSION: Results from this nationwide cohort study showed high non-persistence levels with all OACs and suggest that persistence with both dabigatran and rivaroxaban therapy is not better than persistence with VKA therapy. Hospitalizations for bleeding among non-persistent patients were unlikely to explain these high non-persistence rates.
The tree-based scan statistic is a statistical data mining tool that has been used for signal detection with a self-controlled design in vaccine safety studies. This disproportionality statistic adjusts for multiple testing in evaluation of thousands of potential adverse events. However, many drug safety questions are not well suited for self-controlled analysis. We propose a method that combines tree-based scan statistics with propensity score-matched analysis of new initiator cohorts, a robust design for investigations of drug safety. We conducted plasmode simulations to evaluate performance. In multiple realistic scenarios, tree-based scan statistics in cohorts that were propensity score matched to adjust for confounding outperformed tree-based scan statistics in unmatched cohorts. In scenarios where confounding moved point estimates away from the null, adjusted analyses recovered the prespecified type 1 error while unadjusted analyses inflated type 1 error. In scenarios where confounding moved point estimates toward the null, adjusted analyses preserved power, whereas unadjusted analyses greatly reduced power. Although complete adjustment of true confounders had the best performance, matching on a moderately mis-specified propensity score substantially improved type 1 error and power compared with no adjustment. When there was true elevation in risk of an adverse event, there were often co-occurring signals for clinically related concepts. TreeScan with propensity score matching shows promise as a method for screening and prioritization of potential adverse events. It should be followed by clinical review and safety studies specifically designed to quantify the magnitude of effect, with confounding control targeted to the outcome of interest.
BACKGROUND: Continuation of antiplatelet therapy beyond 12 months after a drug-eluting stent procedure reduced the risk of a major adverse cardiovascular and cerebrovascular event (MACCE) in the DAPT trial (Dual Antiplatelet Therapy). Observational studies have evaluated outcomes related to different durations of therapy but are susceptible to bias.
METHODS AND RESULTS: Using deidentified claims from commercially insured and Medicare populations in the United States, we compared how increasingly stringent definitions of exposure affect associations between antiplatelet continuation versus discontinuation and MACCE, myocardial infarction, and intracerebral hemorrhage or gastrointestinal bleeding in patients meeting DAPT trial inclusion criteria between 2004 and 2013. Therapy continuation at 12 months was defined as (1) having antiplatelet supply on hand versus not (landmark time); (2) refilling within 30 days versus not among individuals with antiplatelet supply; (3) criteria 2 plus continuous prior antiplatelet use; and (4) criteria 2 and 3 plus a cardiologist visit in months 10 to 12. Propensity score-adjusted hazard ratios were compared. Cohort sizes were 53 679, 27 524, 16 971, and 7948, respectively, of which 20% were discontinuers on average. Increasing restriction led to progressively larger associations with continued treatment: cohort 1 MACCE hazard ratio, 0.79 (0.73, 0.87); myocardial infarction, 0.74 (0.65, 0.83); bleed, 1.03 (0.96, 1.11) versus cohort 4 MACCE hazard ratio, 0.66 (0.48, 0.91); myocardial infarction, 0.56 (0.37, 0.86); bleed, 1.24 (0.95, 1.61). Estimates trended toward DAPT trial estimates and were associated with reduced levels of exposure misclassification.
CONCLUSIONS: In an example of long-term antiplatelet use, increasing restrictions on the definition of therapy continuation yielded results consistent with trial estimates by reducing exposure misclassification.
PURPOSE: In this report, we use data from FDA's Sentinel System to focus on how augmenting a diagnosis-based chronic kidney disease cohort with patients identified through laboratory results impacts cohort characteristics and outcomes.
METHODS: We used data from 2 Data Partners. Patients were eligible if they were health plan members on January 1, 2012. We classified chronic kidney disease patients into mutually exclusive categories according to the hierarchy of (1) ICD-9-CM diagnosis (DXGroup), or (2) two estimated glomerular filtration rates <60 mL/min/1.73m , separated by at least 90 days (2-LabGroup), or (3) a single estimated glomerular filtration rates <60 mL/min/1.73m (1-LabGroup). We compared the groups on demographic, clinical, and health care utilization characteristics using pairwise standardized differences. We used Cox regression to compare the groups on mortality, adjusting for baseline covariates.
RESULTS: We identified 209 864 patients: 107 607 in DxGroup (51%) and 102 257 (49%) from laboratory data alone. For every characteristic, the DxGroup was the sickest, followed by the 2-LabGroup and then the 1-LabGroup. The DxGroup was more likely to die than 2-LabGroup (hazard ratio [HR], 1.47; 95% CI, 1.22-1.77) at Site 1; that effect was observed, but attenuated, at Site 2 (HR, 1.16; 95% CI, 1.07-1.25). The DxGroup was more likely to die than the 1-LabGroup at Site 1 (HR, 1.36; 95% CI, 1.20-1.55), but not at Site 2 (HR, 0.94; 95% CI, 0.89-1.00).
CONCLUSIONS: We suggest that drug safety researchers consider whether the method of cohort identification contributes to generalizability of safety findings.
OBJECTIVES: To compare rates of switchbacks to branded drug products for patients switched from branded to authorized generic drug products, which have the same active ingredients, appearance, and excipients as the branded product, with patients switched from branded to generic drug products, which have the same active ingredients as the branded product but may differ in appearance and excipients.
DESIGN: Observational cohort study.
SETTING: Private (a large commercial health plan) and public (Medicaid) insurance programs in the US.
PARTICIPANTS: Beneficiaries of a large US commercial health insurer between 2004 and 2013 (primary cohort) and Medicaid beneficiaries between 2000 and 2010 (replication cohort).
MAIN OUTCOME MEASURES: Patients taking branded products for one of the study drugs (alendronate tablets, amlodipine tablets, amlodipine-benazepril capsules, calcitonin salmon nasal spray, escitalopram tablets, glipizide extended release tablets, quinapril tablets, and sertraline tablets) were identified when they switched to an authorized generic or a generic drug product after the date of market entry of generic drug products. These patients were followed for switchbacks to the branded drug product in the year after their switch to an authorized generic or a generic drug product. Cox proportional hazard models were used to estimate hazard ratios and 95% confidence intervals after adjusting for demographics, including age, sex, and calendar year. Inverse variance meta-analysis was used to pool adjusted hazard ratios across all drug products.
RESULTS: A total of 94 909 patients switched from branded to authorized generic drug products and 116 017 patients switched from branded to generic drug products and contributed to the switchback analysis. Unadjusted incidence rates of switchback varied across drug products, ranging from a low of 3.8 per 100 person years (for alendronate tablets) to a high of 17.8 per 100 person years (for amlodipine-benazepril capsules), with an overall rate of 8.2 per 100 person years across all drug products. Adjusted switchback rates were consistently lower for patients who switched from branded to authorized generic drug products compared with branded to generic drug products in the primary cohort (pooled hazard ratio 0.72, 95% confidence interval 0.64 to 0.81). Similar results (0.75, 0.62 to 0.91) were observed in the replication cohort.
CONCLUSION: Switching from branded to authorized generic drug products was associated with lower switchback rates compared with switching from branded to generic drug products.
BACKGROUND: Nonadherence to systemic treatments for psoriasis leads to treatment failure and increased health care utilization.
OBJECTIVE: Examine drug utilization patterns and adherence of new users of systemic medications for psoriasis.
METHODS: We conducted a retrospective, comparative cohort study using a large US health insurance claims database including psoriasis patients who were new users of acitretin, adalimumab, etanercept, methotrexate, or ustekinumab. Adherence was measured by using proportion of days covered dichotomized as adherent (≥0.80) or nonadherent (<0.80). Odds ratios (ORs) and 95% confidence intervals (CIs) comparing adherence to each exposure (acitretin, adalimumab, etanercept, or ustekinumab) to the referent (methotrexate) were estimated via logistic regression, with pairwise 1:1 propensity score matching to adjust for potential confounders.
RESULTS: In total, 22,742 patients were new users of systemic medications. Among these patients, adherence to adalimumab (OR 2.24, 95% CI 2.05-2.45); etanercept (OR 1.77, 95% CI 1.63-1.92); and ustekinumab (OR 2.54, 95% CI 2.24-2.87) was greater and acitretin (OR 0.57, 95% CI 0.50-0.63) lower compared with methotrexate.
LIMITATIONS: Unable to evaluate reasons for discontinuation.
CONCLUSION: We report greater adherence to biologics than methotrexate in new users. Further research is needed to understand overall low adherence to systemic medications for psoriasis.
Importance: Approximately half of patients with chronic conditions are nonadherent to prescribed medications, and interventions have been only modestly effective.
Objective: To evaluate the effect of a remotely delivered multicomponent behaviorally tailored intervention on adherence to medications for hyperlipidemia, hypertension, and diabetes.
Design, Setting, and Participants: Two-arm pragmatic cluster randomized controlled trial at a multispecialty group practice including participants 18 to 85 years old with suboptimal hyperlipidemia, hypertension, or diabetes disease control, and who were nonadherent to prescribed medications for these conditions.
Interventions: Usual care or a multicomponent intervention using telephone-delivered behavioral interviewing by trained clinical pharmacists, text messaging, pillboxes, and mailed progress reports. The intervention was tailored to individual barriers and level of activation.
Main Outcomes and Measures: The primary outcome was medication adherence from pharmacy claims data. Secondary outcomes were disease control based on achieved levels of low-density lipoprotein cholesterol, systolic blood pressure, and hemoglobin A1c from electronic health records, and health care resource use from claims data. Outcomes were evaluated using intention-to-treat principles and multiple imputation for missing values.
Results: Fourteen practice sites with 4078 participants had a mean (SD) age of 59.8 (11.6) years; 45.1% were female. Seven sites were each randomized to intervention or usual care. The intervention resulted in a 4.7% (95% CI, 3.0%-6.4%) improvement in adherence vs usual care but no difference in the odds of achieving good disease control for at least 1 (odds ratio [OR], 1.10; 95% CI, 0.94-1.28) or all eligible conditions (OR, 1.05; 95% CI, 0.91-1.22), hospitalization (OR, 1.02; 95% CI, 0.78-1.34), or having a physician office visit (OR, 1.11; 95% CI, 0.91-1.36). However, intervention participants were significantly less likely to have an emergency department visit (OR, 0.62; 95% CI, 0.45-0.85). In as-treated analyses, the intervention was associated with a 10.4% (95% CI, 8.2%-12.5%) increase in adherence, a significant increase in patients achieving disease control for at least 1 eligible condition (OR, 1.24; 95% CI, 1.03-1.50), and nonsignificantly improved disease control for all eligible conditions (OR, 1.18; 95% CI, 0.99-1.41).
Conclusions and Relevance: A remotely delivered multicomponent behaviorally tailored intervention resulted in a statistically significant increase in medication adherence but did not change clinical outcomes. Future work should focus on identifying which groups derive the most clinical benefit from adherence improvement efforts.
Trial Registration: ClinicalTrials.gov identifier: NCT02512276.
INTRODUCTION: Nearly 90% of drugs dispensed in the US are generic products.
OBJECTIVE: The aim of this study was to develop and implement a tool for analyzing manufacturer-level drug utilization and switching patterns within the US Food and Drug Administration's Sentinel system.
METHODS: A descriptive tool was designed to analyze data in the Sentinel common data model and was tested with two case studies-metoprolol extended release (ER) and lamotrigine ER-using claims data from four Sentinel data partners. We plotted initiators of each brand and generic product over time. For metoprolol ER, we evaluated rates of switching from generics around the time of manufacturing issues. For lamotrigine ER, we examined rates of switching back to the brand among those who switched from brand to generic.
RESULTS: We identified 1,651,285 initiators of metoprolol ER products between July 2008 and September 2015. We observed a large decrease in monthly metoprolol ER initiators (from 25,465 in December 2008 to 13,128 in February 2009), corresponding to recalls by generic manufacturers. We observed simultaneous increases in utilization of the authorized generic and brand products. We identified 4266 initiators of lamotrigine ER with an epilepsy diagnosis between January 2012 and September 2015. Among those who switched from brand to generic, the cumulative incidence of switching back was close to 20% at 2 years. Switchback rates were higher for the first available generic products.
CONCLUSIONS: This developed tool was able to elucidate novel utilization and switching patterns in two case studies. Such information can be used to support surveillance of generic drugs and biosimilars.
PURPOSE: The Food and Drug Administration's Sentinel System developed parameterized, reusable analytic programs for evaluation of medical product safety. Research on outpatient antibiotic exposures, and Clostridium difficile infection (CDI) with non-user reference groups led us to expect a higher rate of CDI among outpatient clindamycin users vs penicillin users. We evaluated the ability of the Cohort Identification and Descriptive Analysis and Propensity Score Matching tools to identify a higher rate of CDI among clindamycin users.
METHODS: We matched new users of outpatient dispensings of oral clindamycin or penicillin from 13 Data Partners 1:1 on propensity score and followed them for up to 60 days for development of CDI. We used Cox proportional hazards regression stratified by Data Partner and matched pair to compare CDI incidence.
RESULTS: Propensity score models at 3 Data Partners had convergence warnings and a limited range of predicted values. We excluded these Data Partners despite adequate covariate balance after matching. From the 10 Data Partners where these models converged without warnings, we identified 807 919 new clindamycin users and 8 815 441 new penicillin users eligible for the analysis. The stratified analysis of 807 769 matched pairs included 840 events among clindamycin users and 290 among penicillin users (hazard ratio 2.90, 95% confidence interval 2.53, 3.31).
CONCLUSIONS: This evaluation produced an expected result and identified several potential enhancements to the Propensity Score Matching tool. This study has important limitations. CDI risk may have been related to factors other than the inherent properties of the drugs, such as duration of use or subsequent exposures.
A retrospective cohort study, supplemented with a nested case-control study, was performed using two administrative databases from commercial health plans in the United States to compare the incidence of pancreatic and thyroid cancer among users of exenatide versus other antidiabetic drugs (OADs). Patients with type 2 diabetes who initiated exenatide or OADs between 1 June 2005 and 30 June 2015 were included. Pancreatic and thyroid cancers were identified using chart-validated algorithms in the cohort study. Cases in the nested case-control study were chart-confirmed pancreatic or thyroid cancers, and controls were sampled using risk-set sampling. The time-fixed analyses comparing 33 629 exenatide initiators with 49 317 propensity-score-matched OAD initiators yielded hazard ratios of 0.76 (95% confidence interval [CI] 0.47-1.21) for pancreatic cancer and 1.46 (95% CI 0.98-2.19) for thyroid cancer. Results in the time-dependent analyses by cumulative duration or dose were similar. Nested case-control analyses yielded rate ratios of 0.48 (95% CI 0.25-0.91) for pancreatic cancer and 0.87 (95% CI 0.59-1.29) for thyroid cancer. This observational study suggested exenatide use was not associated with an increased risk of pancreatic or thyroid cancer.
Use of disease risk score (DRS)-based confounding adjustment when estimating treatment effects on multiple outcomes is not well studied. We designed an empirical cohort study to compare dabigatran initiators and warfarin initiators with respect to risks of ischemic stroke and major bleeding in 12 sequential monitoring periods (90 days each), using data from the Truven Marketscan database (Truven Health Analytics, Ann Arbor, Michigan). We implemented 2 approaches to combine DRS for multiple outcomes: 1) 1:1 matching on prognostic propensity scores (PPS), created using DRS for bleeding and stroke as independent variables in a propensity score (PS) model; and 2) simultaneous 1:1 matching on DRS for bleeding and stroke using Mahalanobis distance (M-distance), and compared their performance with that of traditional PS matching. M-distance matching appeared to produce more stable results in the early marketing period than both PPS and traditional PS matching; hazard ratios from unadjusted analysis, traditional PS matching, PPS matching, and M-distance matching after 4 periods were 0.72 (95% confidence interval (CI): 0.51, 1.03), 0.61 (95% CI: 0.31, 1.09), 0.55 (95% CI: 0.33, 0.91), and 0.78 (95% CI: 0.45, 1.34), respectively, for stroke and 0.65 (95% CI: 0.53, 0.80), 0.78 (95% CI: 0.60, 1.01), 0.75 (95% CI: 0.59, 0.96), and 0.78 (95% CI: 0.64, 0.95), respectively, for bleeding. In later periods, estimates were similar for traditional PS matching and M-distance matching but suggested potential residual confounding with PPS matching. These results suggest that M-distance matching may be a valid approach for extension of DRS-based confounding adjustments for multiple outcomes of interest.
PURPOSE: To explore generalized boosted modeling (GBM) as a method for identifying subgroups with greater benefit or harm with dabigatran versus warfarin for treatment of atrial fibrillation.
METHODS: We identified new initiators of warfarin or dabigatran with nonvalvular atrial fibrillation in 2 healthcare claims databases (2009-2013) and used GBM within 1 data source (development cohort) to explore subgroups where their effect on thromboembolism and major bleeding may differ. Identified subgroups were evaluated in the second data source (validation cohort) with stabilized-inverse-probability-of-treatment weights to adjust for confounding.
RESULTS: Development and validation cohorts included 13 624 (28% dabigatran) and 62 596 (29% dabigatran) initiators, respectively. In development data, the strongest exposure interactions were prior thromboembolism and renal disease. In validation data, reduction in thromboembolism with dabigatran was greater for patients with versus without a history of thromboembolism by 2.8 (95% CI, -0.5 to 5.4) events per 100 patient-years. Major bleeding was reduced by 1.6/100 patient-years for dabigatran compared to warfarin initiators, without evidence of variation by renal disease.
CONCLUSIONS: We explored use of GBM to identify potential subgroups with different treatment effect. Dabigatran's superiority to warfarin at prevention of thromboembolism may be greater in secondary than primary prevention. In practice, secondary prevention patients are more often treated with warfarin.
Small changes in bioavailability of narrow therapeutic index (NTI) drugs can alter clinical outcomes, raising concern over generic NTI substitution. We surveyed pharmacists to identify their perceptions of generic NTI drugs, their frequency of performing generic NTI substitution, and predictors of this behavior. Of 710 respondents (33% response rate), 87% perceived generic NTI drugs as effective as their brand-name versions and 94% as safe. Whereas 82% almost always performed generic NTI substitution for initial prescriptions, only 60% did for refills. Pharmacists in non-chain settings (odds ratio (OR) = 2.37; 95% confidence interval (CI) = 1.40-4.02), in practice longer (per year OR = 1.04; 95% CI = 1.02-1.06), in states with affirmative patient consent laws (OR = 1.88; 95% CI = 1.06-3.32), and in states with NTI-specific substitution requirements (OR = 1.95; 95% CI = 1.16-3.26) were more likely not to substitute initial prescriptions. Education of non-chain and veteran pharmacists and elimination of affirmative patient consent and NTI-specific substitution requirements could increase generic NTI substitution.
Active surveillance for unknown or unsuspected adverse drug effects may be carried out by applying epidemiological techniques to large administrative databases. Self-controlled designs, like the symmetry design, have the advantage over conventional design of adjusting for confounders that are stable over time. The aim of this paper was to describe the output of a comprehensive open-ended symmetry analysis of a large dataset. All drug dispensings and all secondary care contacts in Denmark during the period 1995-2012 for persons born before 1950 were analyzed by a symmetry design. We analyzed all drug-drug sequences and all drug-disease sequences occurring during the study period. The identified associations were ranked according to the number of outcomes that potentially could be attributed to the exposure. In the main analysis, 29,891,212 incident drug therapies, and 21,300,000 incident diagnoses were included. Out of 186,758 associations tested in the main analysis, 43,575 (23.3%) showed meaningful effect size. For the top 200 drug-drug associations, 47% represented unknown associations, 24% represented known adverse drug reactions, 30% were explained by mutual indication or reverse causation. For the top 200 drug-disease associations the proportions were 31, 15, and 55%, respectively. Screening by symmetry analysis can be a useful starting point for systematic pharmacovigilance activities if coupled with a systematic post-hoc review of signals.