Cardiovascular disease is responsible for a significant number of deaths in the United States. Treatment to reduce the risk for cardiovascular disease using antihypertensive and lipid-lowering agents has been shown to be effective. Despite this, adherence to these regimens is poor and discontinuation rates are high. Patients who are prescribed lipid-lowering agents have one-year discontinuation rates between 15 and 60 percent. This issue also is present in compliance with anti-hypertensives. Poor adherence to treatment regimens is more prevalent in older persons. Antihypertensive and lipid-lowering agents are used concomitantly in patients to reduce cardiovascular risk, but there are no studies that assess adherence to this combination of agents. Chapman and colleagues evaluated the pattern of adherence with concomitant antihypertensive and lipid-lowering medications and assessed patient and regimen characteristics that could predict adherence.
The trial design was a retrospective chart audit of patients enrolled in a managed-care organization during a five-year period. Participants were included in the study if they initiated an antihypertensive and a lipid-lowering regimen within 90 days of each other. Adherence was determined by the number of days covered by a prescription during a three-month period; adherence was defined as filled medication prescriptions to cover at least 80 percent of the days. Additional information collected included demographic and clinical characteristics of each participant. Participants were classified into three categories of coronary heart disease, and comorbid conditions also were recorded.
There were 8,406 patients who met the inclusion criteria for the study. Thirty-four percent of the patients initiated both therapies on the same day, and 37 percent started both medications within 30 days of the physician visit. After three months, only 45 percent of the patients were adherent to both medications; this decreased to 36 percent at six months and remained the same at one year. Patients were more likely to adhere to both medications if they initiated them at the same time. In addition, patients with a history of coronary heart disease or congestive heart failure were more likely to be compliant. Patients taking no other medications were twice as likely to be adherent to concomitant therapy as those who were taking six or more medications. Women were less likely to be compliant than men. Patients 55 to 64 years of age were more likely to adhere to the concomitant regimen than those in other age groups.
The authors conclude that adherence to antihypertensive and lipid-lowering therapy was poor at six months, with approximately one in three patients being compliant. One strategy that may improve adherence is for physicians to start patients on both medications at the same time and, when possible, reduce the number of medications patients are already taking.