Association of Medication Regimen Complexity and Patient Adherence

Patients with ≥1 chronic diseases often require complex therapeutic regimens involving frequent daily dosing and multiple medications. Regimen complexity may undermine effective chronic disease management; patients taking medications that require frequent daily dosing are more likely to be nonadherent to their treatments compared with patients with simpler dosing schedules. According to researchers, interventions that simplify treatment regimens by reducing dosing frequency or by switching patients to fixed-dose medication combinations result in improvements in appropriate medication use. Other factors that add complexity to treatment regimens and may also affect adherence have not been evaluated. For patients prescribed equivalent numbers of medications and with equal levels of illness severity, those who go to the pharmacy numerous times, who have several physicians writing prescriptions for them, or who fill prescriptions at various pharmacies may have greater difficulty remaining adherent to their treatment regimen. Because these factors may be addressed to improve adherence, the researchers recently conducted a study to examine the extent of prescribing and filling complexity in patients prescribed a cardiovascular medication and to assess the association of the regimen complexity with adherence. They reported results in Archives of Internal Medicine [2011;171(9):814-822]. The study utilized prescription claims data from CVS Caremark in Woonsocket, Rhode Island, a pharmacy benefit manager with >50 million beneficiaries throughout the United States. The study cohort consisted of individuals prescribed a statin (n=1,827,395) or an angiotensin-converting enzyme inhibitor or renin angiotensin receptor blocker (ACEI/ARB) (n=1,480,304) between June 1, 2006, and May 30, 2007. Adherence was estimated by calculating the number of days the medication was available (proportion of days covered) for each drug class prescribed over the 12-month adherence assessment period. Of the total sample, 20.1% (n=664,675) were included in the study groups. In both groups, mean age was 63 years, 49% were male, mean income was >$50,000 per year, and the majority received drug coverage directly through employer-sponsored insurance or via a health plan. In the statin cohort, during the 3-month complexity assessment period, patients filled a mean of 11.4 medications at 5.0 visits to the pharmacy. The majority (9.7) of fills were for maintenance medications and represented a mean of 5.9 different drug classes. On average, the prescriptions were written by 2 different prescribers and filled at 1 pharmacy. The medication filling patterns were similar in the ACEI/ARB cohort. Patients took ACEI/ARB medications a mean of 1.1 times per day; 10% filled prescriptions for an ACEI/ARB with instructions to take it ≥2 times per day. Mean medication adherence in the statin group was 68.6%; in the ACEI/ARB group, it was 66.4%. Following adjustment for demographics, comorbidity, and copayments, independent predictors of lower adherence were a greater number of prescriptions, visits to more pharmacies, and less refill consolidation, the study found. For example, each added pharmacy at which patients filled a prescription during the 3-month complexity assessment window was associated with a 1.6 percentage point reduction in statin adherence over the subsequent year. In adjusted models, patients with less refill consolidation had adherence rates 8% lower over the subsequent year compared with those with the greatest refill consolidation. In conclusion, the researchers stated, “our analysis of patients filling prescriptions for 2 common cardiovascular medication classes demonstrates the substantial complexity that health system factors contribute to medication use by patients with chronic disease and the negative impact of this complexity on medication adherence.”