Pharmacy & Therapeutics - November 2008 - (Page 653)

Switching from Fixed-Dose to Free-Combination Antihypertensive Medications average annual costs of cardiovascular-related care were $726 for the FDC patients and $1,600 for the two-tablet FC group. In a study by Gerbino et al.,18 better compliance was noted with amlodipine/benazepril than with an ACE-inhibitor plus a dihydropyridine calcium-channel blocker, independent of the number of concomitant medications used. Therapeutic regimens that improve medication persistence and compliance are more likely to produce better health outcomes and lower health care costs. Several studies have demonstrated the positive correlation between persistence and compliance rates and control of hypertension.21–24 In addition to the link between compliance and BP control, studies have shown an inverse relationship between compliance with medication regimens and health care costs in the treatment of hypertension.25–34 Inadequate control of BP has been associated with a significant cost burden35,36 in treating avoidable complications37 such as congestive heart failure,38 coronary heart disease,37,38 stroke,39 and renal disease.40,41 Because hypertension is highly prevalent, with estimated direct and indirect costs of $66.4 billion in the U.S. in 2007,1 improved management of hypertension through better medication compliance has the potential to reduce costs of a disease that generates a significant cost burden in the U.S. • had to have filled prescriptions for an FDC medication for three or more months before the date on which they switched to the FC regimen (the study index date). • were required to have an index date on or after January 1, 2004. • had to have had medical and pharmacy coverage for 12 months before the index date and for 12 or more months after the index date. • had to have a diagnosis of hypertension within 12 months before the index date, according to the International Classification of Diseases-9 (ICD-9-CM 401.XX–404.XX). • had to have initial prescriptions for each compound of the FC regimen with fill dates within 15 days of each other to identify the switch to the FC regimen. • had to have two or more prescriptions for each compound after the index date. Comparable cohorts of patients not switching from FDC medications were identified separately for each of the three combinations according to a propensity-matching algorithm.42,43 The nearest-neighbor method was used to match FDC patients to FC patients, in a 1:1 ratio, according to: • • • • age (younger than 45, 45 to 64, and 65 years and older). sex. payer type (Medicare or commercial insurance). medical comorbidities and risk factors identified from claims diagnoses in the six months prior to the index (i.e., diabetes, tobacco use, time from a prior acute MI, prior heart failure, chronic obstructive pulmonary disease, and lipid disorder). STUDY OBJECTIVE Evidence is limited on the impact of persistence and compliance when patients are switched from FDC to FC antihypertensive regimens. We sought to compare patients who were switched from a FDC to the corresponding free combination of the same medications with patients who continued taking FDC antihypertensive regimens. We hypothesized that patients continuing with FDC hypertension drugs would be more persistent and compliant than patients who were switched to FC medications. Our second hypothesis was that increased compliance would reduce the use of resources and expenditures for total hypertensionrelated health care as a result of improved management of hypertension. For each FC patient, the FDC patient with the closest match in propensity score was selected and was assigned an index date so that the duration of FDC therapy prior to the assigned index date matched the length of FDC therapy prior to the index date of the FC match. Like the FC cohort, the selected FDC patients had to have medical and pharmacy coverage 12 months before the index date and 12 months after the index date. METHODS A retrospective cohort study was conducted to compare: • persistence and compliance with an antihypertensive regimen for patients switching from FDC therapy to FC therapy, consisting of the same compounds, versus patients continuing to take FDC medications. • hypertension-related utilization of health care resources and expenditures for both cohorts. All study data were obtained from the Thomson Medstat MarketScan database, which was compliant with HIPAA regulations and contained medical and pharmacy insurance claims obtained from more than 100 health insurance payers. Measurement of Outcomes Using pharmacy claims data, we measured medication persistence by the percentage of patients continuing therapy without a lapse in therapy of more than 30 days from the date of end of supply of the prior prescription during the 12-month followup period after the study index date. Thus, FDC patients were classified as “not persistent” after a lapse of more than 30 days without a supply of their FDC medication available. For example, a patient in the FDC cohort with prescriptions for 30-day supplies of the medication, with each one to be filled on the dates of January 1, 2004, February 15, 2004, March 31, 2004, and none thereafter, would no longer be “persistent” as of April 30, 2004. FC patients were classified as “not persistent” if they had a lapse of more than 30 days without a supply of both medications available each day. Days on which only one drug was available were considered to represent a lapse in therapy. As an example of persistence within the FC cohort, a patient was taking an ARB plus HCTZ. The patient had prescriptions Sample Selection We evaluated patients who switched from three FDCs: an ARB/HCTZ, an ACE-inhibitor/HCTZ, and an ACE-inhibitor/ calcium-channel blocker. To be eligible for enrollment, members of the sample: Vol. 33 No. 11 • November 2008 • P&T® 653

Table of Contents Feed for the Digital Edition of Pharmacy & Therapeutics - November 2008

Pharmacy & Therapeutics - November 2008 Contents Editorial Medication Errors Prescription: Washington New Drugs/Drug News/New Medical Devices Drug Forecast Heparin-Induced Thrombocytopenia Medication Utilization Patterns and Hypertension-Related Expenditures among Patients Who Were Switched From Fixed-Dose to Free-Combination Antihypertensive Therapy European Society for Medical Oncology and Association for the Study of Bone and Mineral Research Pharmaceutical Approval Update

Pharmacy & Therapeutics - November 2008

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