Patients with cardiovascular disease face "enormous complexity" in managing their prescriptions, and it directly interferes with their adherence to medication, according to a study published online May 9 in Archives of Internal Medicine.
Streamlining this complexity may improve adherence, and thus morbidity and mortality, in this patient group, said Dr. Niteesh K. Choudhry of the division of pharmacoepidemiology and pharmacoeconomics, Brigham and Women’s Hospital and Harvard Medical School, Boston, and his associates.
Using prescription claims data from CVS Caremark during a 1-year period, the investigators assembled a nationally representative cohort of patients taking long-term cardiovascular medications. They chose patients taking a statin, an angiotensin-converting enzyme inhibitor or a renin angiotensin receptor blocker (ACEI/ARB), or both, because these agents "represent the two most widely sold therapeutic classes to treat cardiovascular disease in the United States."
Therapeutic complexity was assessed by measuring the total number of prescriptions filled, the number of fills for medications in different drug classes, the number of physicians who wrote prescriptions, the number of pharmacies used, the number of pharmacy visits the patients made, and the number of daily medication doses that were prescribed.
The researchers also estimated patient adherence by calculating the number of days the medication was available.
The statin cohort comprised 1,827,395 patients and the ACEI/ARB cohort comprised 1,480,304 patients. A total of 20% of the total sample took both classes of drugs.
The mean patient age was 63 years, and the cohort was evenly divided between men and women. Mean income was greater than $50,000 per year, and most patients received drug coverage directly through employer-sponsored insurance or a health plan. Thus, the study findings may not apply to uninsured patients.
During a 3-month "complexity assessment" period, patients filled a mean of 11 medications in six different drug classes at five visits to a pharmacy, from prescriptions written by an average of two physicians.
"More striking, during this same time frame, 10% of patients filled prescriptions for 23 or more medications, 12 or more unique medications, and 11 or more different drug classes; had prescriptions written by four or more prescribers; filled them at two or more pharmacies; and made 11 or more visits to a pharmacy," Dr. Choudhry and his colleagues wrote (Arch. Intern. Med. 2011;171:814-22).
Overall, mean medication adherence was 69% with statins and 66% with ACEI/ARBs.
After the data were adjusted to control for demographic factors, comorbidities, and copayments, patients who visited more pharmacies and those who filled fewer medications per visit (that is, had less refill consolidation) were found to be substantially less adherent to their prescribed therapy.
For example, each additional pharmacy at which a patient filled a prescription was associated with a nearly 2% reduction in statin adherence. Patients who filled the fewest prescriptions per pharmacy visit – those who had the least refill consolidation – had adherence rates that were 8% lower than adherence rates of patients who had the highest refill consolidation.
"The magnitude of these effects [was] particularly large for patients who had newly initiated therapy and who filled their prescriptions at both retail pharmacies and via mail order," the investigators wrote.
"These results highlight an essential aspect of the therapeutic cascade that may be particularly burdensome and which few clinicians likely consider when making prescribing decisions. As such, our findings highlight the potential benefit of efforts to reduce prescribing and filling complexity by encouraging filling by mail order and/or reducing the frequency with which they must fill (e.g., by providing 90-day supplies of medications)," Dr. Choudhry and his colleagues said.
This study was limited in that the investigators were unable to determine why patients filled prescriptions on multiple visits or at multiple pharmacies, to account for unmeasured factors such as patients’ health-seeking behavior or organizational skills, or to account for differences in insurance plans that may have affected prescription-related behavior, they added.
In an accompanying editorial, Dr. Amanda H. Salanitro and Dr. Sunil Kripalani said that despite its limitations, this study "provides a valuable step forward in measuring the complexity of prescription medication management and its effect on adherence." Previous research has focused on the number of medications, the number of doses, and the times of administration, failing to take into account that many patients have multiple prescribers, shop around for lower prices, use both mail order and retail pharmacies, and have refills due on different dates.
To improve adherence, physicians "can encourage patients to simplify their pattern of filling medications by using a single pharmacy or synchronizing refill dates. Having a pharmacy ‘home’ ... might also be helpful for maintaining an accurate medication list and avoiding drug-drug interactions.