Effect of pharmaceutical formulation of diltiazem on the utilization of medicaid and health maintenance organization services

Abstract Hypertension is a silent disease, the full seriousness of which becomes evident only when the sequelae of long-standing high blood pressure are manifest as congestive heart failure, angina, myocardial infarction, cerebral vascular accident, or end-stage renal disease. A major barrier to the management of hypertension is the extent to which patients comply with treatment. We report the findings of retrospective analyses designed to determine the relationship between dosage formulation and administration schedule for the calcium channel antagonist diltiazem, and the utilization of health care services within the state of South Carolina's Medicaid program and a network-model health maintenance organization (HMO). The research objectives were threefold: (1) for patients prescribed 180 mg/d of diltiazem, compare financial outcomes of patients receiving three dosage formulations: 60 mg three times daily (TID), immediate-release (IR) diltiazem; 90 mg two times daily (BID), sustained-release (SR) diltiazem; or 180 mg once daily (QD), controlled-delivery (CD) diltiazem; (2) for patients prescribed 240 mg/d of diltiazem, compare financial outcomes of patients receiving three dosage formulations: 60-mg four times daily (QID) diltiazem IR, 120-mg BID diltiazem SR, or 240-mg QD diltiazem CD; and (3) determine the effect of the medication possession ratio (MPR), an index of compliance, on health service utilization. Multivariate regression analysis was used to determine the incremental influence of selected demographic characteristics, use of medical services 6 months before the diagnosis of hypertension, and the prescribed formulation of diltiazem on health service expenditures 1 year after the diagnosis of hypertension. Results indicate that patients initially prescribed a formulation and regimen facilitating once-daily administration have the fewest number of changes in antihypertensive pharmacotherapy, require fewer concomitant antihypertensives, achieve the highest MPR for antihypertensive pharmacotherapy, and record a decrease in the use of and expenditures for physician and hospital services ( P ≤ 0.05) under Medicaid and within the HMO.