Pharmacy & Therapeutics - May 2008 - (Page 288) Effect of Persistence with Drug Therapy On the Risk of Myocardial Re-infarction Fadia T. Shaya, PhD, MPH; Anna Gu, PhD, MS; and Xia Yan, MS ABSTRACT Objective: We conducted a study to assess the effect of persistence with therapy in the use of statins, beta blockers, or calcium-channel blockers on the recurrence of myocardial infarction or death in a Medicaid high-risk, largely female, African-American population. Study Design: This was a prospective nonconcurrent cohort, longitudinal data analysis of medical and pharmacy claims of acute myocardial infarction (AMI) patients from Medicaid managed care organizations between January 1, 2002, and December 31, 2004. Methods: Cox proportional hazards models were used to predict the likelihood of a re-infarction as a function of persistence with the use of the initial medication after an AMI. We made adjustments for age, race, sex, heart disease, and other comorbidities as well as the pharmacotherapies prescribed. Results: Among 515 AMI patients (58.1% female, 46% African-American), the most prevalent comorbidities were hypertension (90.9%) and heart disease (80.6%). Most initial AMIs were non-transmural. Discontinuation of statins, beta blockers, or calcium-channel blockers after an AMI increased the likelihood of a re-infarction (hazard ratio, 1.66; 95% confidence interval, 1.03–2.69). Concurrent heart disease, hyperlipidemia, or renal disease significantly increased the probability of having a re-infarction, but age, race, and sex did not significantly predict the likelihood of re-infarction or death. Conclusion: Persistence of therapy in the use of the initial AMI-preventive medication after an AMI was effective in avoiding re-infarction or death. Heart disease, renal disease, and hyperlipidemia increased the likelihood of an adverse outcome. BACKGROUND Acute myocardial infarction (AMI) is the leading cause of death in the U.S. as well as in most industrialized nations throughout the world.1 In the U.S., more than 800,000 people are affected by MI, and despite an increased awareness of its warning signs, 250,000 die before they reach the hospital. The risk of illness and death in survivors of the acute stage of MI is as much as 15 times higher than in the general population, Dr. Shaya is Associate Professor in the Department of Pharmaceutical Health Services Research at the University of Maryland’s School of Pharmacy in Baltimore, Maryland. At the time of this writing, Dr. Gu was a Graduate Research Assistant and doctoral student at the university. She is currently an Associate Consultant for Analysis Group, Inc., in Boston, Massachusetts. Ms. Yan is a doctoral student in the Department of Pharmaceutical Health Services Research at the University of Maryland. and approximately two-thirds of these patients do not make a full recovery.2 Drug therapy plays a key role after an AMI. Guidelines from North America and Europe recommend calcium-channel blockers, beta blockers, and statins as major therapeutic options.1,3,4 Evidence from clinical trials and real-world practice have confirmed the efficacy and effectiveness of these agents in reducing the risk of re-infarction and all-cause mor tality. For example, in a study by McCormick et al., the risk of cardiovascular death and nonfatal re-infarction was reduced by 22% and 27% with beta blockers, by 13% and 31% with long-term therapy with angiotensin-converting enzyme (ACE)–inhibitors, and by 14% and 25% with lipid-lowering medications, respectively.5 To a large extent, the success of a treatment strategy is determined by the compliance of the patient. A study by Rasmussen et al. in 2007 demonstrated substantially higher rates of re-infarction and death among post-AMI survivors with less than optimal compliance with drug therapy.6 Other known risk factors include male sex, advancing age, a family history of cardiovascular disease (CVD), overweight or obesity, and lifestyle factors (cigarette smoking, sedentary habits, and overconsumption of alcohol).7–9 The goal of our study was to investigate the association between persistence with preventive medication for AMI and the risk of death or re-infarction in a Medicaid population. We focused on Medicaid beneficiaries for two reasons. First, these patients represent a vulnerable group with compromised cardiovascular health conditions and high rates of drug nonpersistence.10,11 Second, study medications are free of charge for patients who are covered by Medicaid managed care plans. Therefore, persistence with therapy should be a behavior that is unaffected by the ability to afford it. To our knowledge, no studies have focused on minority or high-risk populations who are covered by Medicaid managed care plans. We examined the association between the persistence of use of calcium-channel blockers, beta blockers, or statins and the likelihood of re-infarction or death after adjusting for demographic and clinical characteristics. METHODS Sources of Data The study population consisted of more than 400,000 Medicaid recipients from a mid-Atlantic state. Recipients must have been enrolled in one of eight prepaid, contracted managed care organizations (MCOs). Enrollees included those who qualified because of their low incomes or those who had high medical expenses relative to their income. The population was predominantly female and African-American. Disclosure: The authors have no commercial or financial relationships to disclose in regard to this article. Accepted for publication March 18, 2008. 288 P&T® • May 2008 • Vol. 33 No. 5
For optimal viewing of this digital publication, please enable JavaScript and then refresh the page. If you would like to try to load the digital publication without using Flash Player detection, please click here.