Lower copayments, access to mail order pharmacies—especially when combined with financial incentives to use such pharmacies—and choice of first-line therapy all positively influence medication compliance among new users of antihypertensive drugs, according to a study published online Dec. 10 in the Archives of Internal Medicine. “The study is important because we identified specific policy-level system interventions that have a beneficial influence on medication adherence … and the interventions were effective across [various demographics],” lead author Alyce Adams, PhD, of Kaiser Permanente Division of Research in Oakland, Calif., told Cardiovascular Business in an interview.
Adams and colleagues conducted a retrospective study of 44,167 patients enrolled in the Kaiser Permanente Health System who were initially prescribed medication for hypertension in 2008. The researchers extracted clinical records from integrated EHRs, including pharmacy records, at Kaiser Permanente Northern California.
Patients were classified by race: 37 percent white (non-Hispanic); 6.9 percent black non-Hispanic; 8.8 percent Asian; 10.1 percent Hispanic, and 37.2 percent either “other” or “unknown.” Patients were divided into three groups based on medication adherence. Primary nonadherence was a failure to fill a prescription within two months of the date it was ordered. Early nonpersistence was failing to obtain a refill within 90 days of the date of the initial prescription fill. Nonadherence was not having medication available for 20 percent or more of the days in the first 12 months after filling the initial prescription.
Primary nonadherence was low (5 percent) and similar across ethnic groups. Unadjusted prevalence of early nonpersistence ranged from 11.3 percent among those of other or unknown racial background to 42.5 percent among blacks. Unadjusted nonadherence ranged from 17.1 percent in whites to 28.1 percent in blacks.
The researchers found that a prescription copayment of less than $6 was associated with better rates of medication adherence, as was enrollment in a mail order pharmacy. When information about copayments and mail order pharmacy use was included in the analysis, the researchers found the racial disparity in overall nonadherence was attenuated. The adjusted odds ratio for nonadherence was 1.55 for blacks, 1.13 for Asians, 1.46 for Hispanics, and 1.01 for unknown/other.
At baseline, more than 60 percent of the patients in the study had uncontrolled high blood pressure. That number dropped to 20 percent uncontrolled by the end of the 12-month period following initiation of antihypertension treatment. Nonpersistent blacks had the highest rates of uncontrolled blood pressure (28.2 percent); adherent Asians had the lowest rates (14.1 percent).
The authors noted that many previous studies had identified race as a predictor of noncompliance with a medication regimen, and emphasized that lower copayments and use of mail order pharmacies increased adherence across racial categories. “For those of us working in medication adherence, the persistence of the [racial] disparities has been disconcerting," Adams said. "We have found system-level interventions that are effective in easing the disparity in adherence and lowering uncontrolled hypertension. Going forward we need to identify other types of interventions that are being used, see if they are working and if so, understand why they’re working.”
The researchers also found differences in adherence behavior associated with the type of drug initially prescribed, and their data demonstrated that ethnicity had an impact on how patients would adhere to therapy with the drug. For example, Hispanics who initiated therapy with beta blockers and Asians who initiated therapy with angiotensin-converting enzyme inhibitors had a higher likelihood of nonpersistence than others of the same racial classification who were prescribed other drugs.
“There may be something about the patients prescribed these drugs that leads to greater incidence of early nonadherence, but we could not control for it in our study. More clinical input from the treating physicians may lead to better identification of the causes … and help us understand how we might intervene to encourage medication adherence in these patients,” Adams said.