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Purpose: Immediate‐release forms of generic mixed amphetamine salts (MAS) have been the subject of passive surveillance reports signaling lack of effectiveness. We examined switching patterns that might suggest whether long‐term users of specific MAS are more likely to switch away or switch back after use of the MAS of interest in the FDA's Sentinel Distributed Database. Methods: We required at least 60‐day continuous supply of selected MAS grouped by Abbreviated New Drug Application (ANDA) to describe patterns of switching away from and to generics approved under the ANDAs of interest among individuals ages 15–64 years with attention deficit hyperactivity disorder or narcolepsy during 2013–2019. Results: We observed the greatest number of treatment episodes for ANDA 040422 (n = 525 771), followed by ANDA 202424 (n = 181 693), ANDA 040439 (n = 62 363), ANDA 040440 (n = 21 143), and ANDA 040480 (n = 8792). Of those with switches away from their original ANDA, episodes initiated on generic products under ANDA 040422 (48.6%) and ANDA 202424 (43.0%) were most likely to switch back, while those initiated on generic product under ANDA 040480 were least likely (24.1%). Of those episodes with switches to a generic under an ANDA of interest, about one‐third (range 27.1% to 37.0%) switched back to the same product. These switches back had a median time to switch of about 30 days. Conclusions: These descriptive analyses, although subject to limitations, did not suggest increased switching away or switching back after use of the generics of interest. Continued post‐marketing surveillance is warranted. [ABSTRACT FROM AUTHOR]

The anticoagulant response to warfarin, a narrow therapeutic index drug, increases with age, which may make older patients susceptible to adverse outcomes resulting from small differences in bioavailability between generic and brand products. Using US Medicare claims linked to electronic medical records from two large hospitals in Boston, we designed a cohort study of ≥ 65‐year‐old patients. Patients were followed for a composite effectiveness outcome of ischemic stroke or venous thromboembolism, a composite safety outcome, including major hemorrhage, and a 1‐year all‐cause mortality outcome. After propensity score fine‐stratification and weighting to account for > 90 confounders, hazard ratios comparing brand vs. generic warfarin initiators (95% confidence intervals) for the effectiveness, safety, and all‐cause mortality outcomes, were 0.97 (0.65–1.46), 0.94 (0.65–1.35), and 0.84 (0.62–1.13), respectively. Results from subgroup analyses of patients with atrial fibrillation, CHADS‐VASc score ≥ 3, and HAS‐BLED score ≥ 3 were consistent with the primary analysis. [ABSTRACT FROM AUTHOR]

Background: Some classes of drugs have lower than optimal uptake of generic products. We aimed to understand the determinants of generic drug substitution across classes. Methods: We conducted a cross-sectional analysis of data from the 2013 MarketScan Commercial Claims and Encounters Database from Truven Health Analytics. We quantified generic substitution rates (GSR) for 26 drug classes, choosing one representative week in November 2013. We used mixed-effects logistic regression to estimate the independent relationship between the determinants of interest and generic substitution for 8 classes with low generic utilization. Results: The GSRs for most classes exceeded 90%, although some were much lower including thyroid hormones (64%), androgens (74%), estrogens (71%), and hydantoin-type anticonvulsants (72%). The determinants of generic substitution varied across classes, albeit with important patterns. Patients using a mail order pharmacy had significantly less generic substitution than patients filling at retail pharmacies for 5 of the 8 studied classes; two additional classes showed no relationship between pharmacy type and generic use. Men relative to women and patients taking more medications were more likely to use generics for most classes. State substitution laws and patient consent laws were largely inconsequential regarding generic substitution. Conclusions: Policies are needed to support the use of safe, effective and often lower cost generic drugs, when available. Mail order pharmacies, as often required by pharmacy benefits managers, lessen generic use for many classes. These pharmacies may require additional regulatory oversight if this adversely impacts patients. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Study Objective Generic drugs contain identical active ingredients as their corresponding brand drugs and are pharmaceutically equivalent and bioequivalent, whereas authorized generic drugs (AGs) contain both identical active and inactive ingredients as their corresponding brand drugs but are marketed as generics. This study compares generic-to-brand switchback rates between generic and AGs. Design Retrospective cohort study. Data Source Claims and electronic health record data from a regional U.S. health care system. Patients The full cohort consisted of 5542 unique patients who received select branded drugs during the 6 months prior to their generic drug market availability (between 1999 and 2014) and then were switched to an AG or generic drug within 30 months of generic drug entry. For these patients, 5929 unique patient-drug combinations (867 with AGs and 5062 with generic drugs) were evaluated. Measurements and Main Results Ten drugs with AGs and generics marketed between 1999 and 2014 were evaluated. The date of the first generic prescription was considered the index date for each drug, and it marked the beginning of follow-up to evaluate the occurrence of generic-to-brand switchback patterns over the subsequent 30 months. Switchback rates were compared between patients receiving AGs versus those receiving generics using multivariable Cox proportional hazards models, controlling for individual drug effects, age, sex, Charlson Comorbidity Score, pre-index drug use characteristics, and pre-index health care utilization. Among the 5542 unique patients who switched from brand to generic or brand to AG, 264 (4.8%) switched back to the brand drug. Overall switchback rates were similar for AGs compared with generics (hazard ratio [ HR] 0.86, 95% confidence interval [ CI] 0.65-1.15). The likelihood of switchback was higher for alendronate ( HR 1.64, 95% CI 1.20-2.23) and simvastatin ( HR 1.81, 95% CI 1.30-2.54) and lower for amlodipine ( HR 0.27, 95% CI 0.17-0.42) compared with the other drugs evaluated. Conclusion Overall switchback rates were similar between AG and generic drug users, indirectly supporting similar efficacy and tolerability profiles for brand and generic drugs. Reasons for differences in switchback rates among specific products need to be explored further. [ABSTRACT FROM AUTHOR]

Page 432, Fig. 2 Plots of model-based outcome incidence rates (per 100 person-years of exposure) before and after introduction of first generic versions of study and control drugs. [ABSTRACT FROM AUTHOR]