Impact of monthly prescription cap on medication persistence among patients with hypertension, hyperlipidemia, or diabetes

Background: Hypertension, hyperlipidemia, and diabetes are among the most prevalent and costly chronic health conditions affecting the U.S. population. Prescription treatments for these conditions are of critical importance to the health of patients, yet suboptimal adherence to prescription treatments for these conditions is not uncommon. While monthly prescription restriction has become a commonly used mechanism to reduce medication utilization, little is known about the effect of this policy on patients with hypertension, hyperlipidemia, or diabetes. Objectives: To evaluate the effect of a reimbursement limit implemented in the Louisiana Medicaid program that restricted patients receiving 8 prescriptionsper month without prior authorization on continuation (persistence) of medications for hypertension, hyperlipidemia, or diabetes. Methods: A pre-post design was applied using Medicaid claims data from 2001-2003 to compare medication persistence among patients in Louisiana (LA) to patients in Indiana (IN), a nonequivalent comparator state. Medication persistence was defined as time from treatment initiation to a treatment gap of 30 days or longer. To capture pre-intervention trends in medication persistence, we compared historical "pre-policy" cohorts in LA and IN followed for 10 months prior to policy adoption (March 3, 2002, to December 31, 2002) to "post-policy" cohorts followed for 10 months after policy adoption (March 3, 2003, to December 31, 2003). All incident cohorts were identified using a 6-month washout period. We used Cox-proportional hazard models to compare discontinuation rates in LA and IN across the pre-policy and policy period cohorts. Results: The adjusted results showed no differences in persistence during the pre-policy period between LA and IN for any of the 3 chronic conditions. In the post-policy period, patients with hyperlipidemia in LA were 1.13 (95% CI =1.02-1.25; P < 0.05) times more likely to discontinue their treatment as their IN counterparts, while no significant differences were observed in the hypertension or diabetes cohorts. Conclusion: Our study suggests there is inconclusive evidence that the monthly prescription restriction disrupts the continuation of medications for common chronic health conditions in patients. More research is needed to identify which patients are most vulnerable to the effect of monthly prescription limits and how this policy could potentially affect additional treatment outcomes such as medication adherence, health outcomes, and Medicaid expenditures.