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Background: Although cholesterol-lowering medications can reduce the risk of recurrent cardiovascular events, premature discontinuation limits effectiveness. Discontinuation rates have not been systematically reported for lipid-lowering trials., Methods and Results: We evaluated medication discontinuation in IMPROVE-IT (Improved Reduction of Outcomes: Vytorin Efficacy International Trial), which evaluated placebo+simvastatin versus ezetimibe+simvastatin in patients hospitalized with the acute coronary syndrome and followed longitudinally postdischarge. Reasons for discontinuation were evaluated from randomization through study end (median 71.9 [interquartile range 51.8-85.8] months). Kaplan-Meier (KM) discontinuation rates were evaluated at 30 days, 1 year, and through year 7, and compared by treatment arm and region, with Cox proportional hazards modeling used to evaluate predictors of discontinuation. Overall, 46.7% of subjects discontinued study medication (KM rate by study end 50.9% [95% CI, 50.1%-51.7%]). The risk of discontinuation was highest early in the trial but decreased with increasing time, with a terminal KM rate per 100 person-years of 8.4 (8.2-8.6) from years 1 to 7. Discontinuation was higher in the placebo+simvastatin versus ezetimibe+simvastatin arm (KM rate 52.0% versus 49.8%, P=0.049) and was highest in the United States (7-year KM rate 57.4%). In multivariable modeling, smoking, prior revascularization, hypertension, unstable angina, female sex, nonwhite race, and US location were associated with higher discontinuation rates., Conclusions: Although discontinuation was highest early and stabilized to 8% per year, because of prolonged follow-up, most discontinuation occurred after year 1. Adding ezetimibe to statin therapy did not increase discontinuation risk. Geographic differences and patient-level factors should be considered in trial design and analysis., Clinical Trial Registration: URL: https://www.clinicaltrials.gov . Unique identifier: NCT00202878.

Background: Patients with diabetes mellitus and cardiovascular disease may not achieve adequate low-density lipoprotein cholesterol (LDL-C) lowering on statin monotherapy, attributed partly to atherogenic dyslipidemia. More intensive LDL-C-lowering therapy can be considered for these patients. A previous randomized, controlled study demonstrated greater LDL-C lowering in diabetic patients with symptomatic cardiovascular disease who switched from simvastatin 20 mg (S20) or atorvastatin 10 mg (A10) to combination ezetimibe/simvastatin 10/20 mg (ES10/20) therapy, compared with statin dose-doubling (to S40 or A20) or switching to rosuvastatin 10 mg (R10). The effect of these regimens on novel biomarkers of atherogenic dyslipidemia (low- and high-density lipoprotein particle number and lipoprotein-associated phospholipase A2 [Lp-PLA2]) was assessed., Methods and Results: Treatment effects on low- and high-density lipoprotein particle number (by NMR) and Lp-PLA2 (by ELISA) were evaluated using plasma samples available from 358 subjects in the study. Switching to ES10/20 reduced low-density lipoprotein-particle number numerically more than did statin dose-doubling and was comparable with R10 (-133.3, -94.4, and -56.3 nmol/L, respectively; P>0.05). Increases in high-density lipoprotein particle number were significantly greater with switches to ES10/20 versus statin dose-doubling (1.5 and -0.5 μmol/L; P<0.05) and comparable with R10 (0.7 μmol/L; P>0.05). Percentages of patients attaining low-density lipoprotein particle number levels <990 nmol/L were 62.4% for ES10/20, 54.1% for statin dose-doubling, and 57.0% for R10. Switching to ES10/20 reduced Lp-PLA2 activity significantly more than did statin dose-doubling (-28.0 versus -3.8 nmol/min per mL, P<0.05) and was comparable with R10 (-28.0 versus -18.6 nmol/min per mL; P>0.05); effects on Lp-PLA2 concentration were modest., Conclusions: In diabetic patients with dyslipidemia, switching from statins to combination ES10/20 therapy generally improved lipoprotein subclass profile and Lp-PLA2 activity more than did statin dose-doubling and was comparable with R10, consistent with its lipid effects., Clinical Trial Registration: URL: http://www.clinicaltrials.gov. Unique identifier: NCT00862251., (© 2015 The Authors. [Ngoc‐Anh Le and Peter W. F. Wilson] and Merck Sharp & Dohme Corp., a subsidiary of Merck & Co., Inc., Kenilworth, NJ, USA. All rights reserved. Published on behalf of the American Heart Association, Inc., by Wiley Blackwell.)