Medicaid Prescription Drug Access Restrictions: Exploring the Effect on Patient Persistence With Hypertension Medications

Published Online: January 15, 2005
Jerome Wilson, PhD; Kirsten Axelsen, MS; and Simon Tang, MPH

Objective: To compare rates of discontinuation of prescription therapy for hypertension in Medicaid patients with and without medication access restrictions.

Study Design: Retrospective cohort study.

Methods: Prescription data were extracted from a pharmacy claims database in a large state that implemented a Medicaid preferred drug list (PDL), both before and after the PDL was implemented. Prescriptions filled between June 2000 and May 2003 were included.

Results: Medicaid patients taking prescription medications commonly used to treat hypertension were 39% (odds ratio = 1.39; 95% confidence interval, 1.21, 1.6) more likely to discontinue hypertension therapy after the restriction was implemented compared with Medicaid patients 1 year earlier when there were no restrictions. Patients were classified as "discontinued" if they had therapy available less than 50% of the time during the 12 months after implementation of the PDL. Before the PDL, 17% of patients receiving treatment with hypertension medication discontinued therapy. After the PDL, 21% of Medicaid patients taking hypertension medication discontinued therapy. After the PDL, Medicaid patients were significantly more likely to switch medications from a restricted to an unrestricted drug. Those patients also were less likely to have a restricted drug added to their therapy regimen.

Conclusions: After implementation of the PDL, Medicaid patients were more likely to discontinue filling prescriptions for antihypertensive medication. Because hypertension management is an important challenge within the Medicaid community, the potential connection between access restrictions and patient adherence to medication therapy is a worthy topic for further exploratory studies and quantitative outcomes research.

(Am J Manag Care. 2005;11:SP27-SP34)

Cardiovascular disease, including high blood pressure, coronary heart disease, congestive heart failure, and stroke, affects nearly 65 million Americans (23% of the total US population), and is responsible for more than 931 000 deaths each year.1,2 According to the National Health And Nutrition Examination Survey 1999-2000, hypertension affects approximately 28% of the adult population in the United States,3 with expenditures estimated at $55 billion a year1 ($21 billion in drugs and medical durables). Despite the significant amount spent on medicines, one potentially important reason why overall direct expenditures are high is patient nonadherence and non-persistence with medications, particularly medications for cardiovascular disease. Among Medicaid patients, hypertension medications are among the most frequently used and highest-payment drug categories.4 It follows that states faced with limited budgets would seek to reduce Medicaid spending on hypertension medicine. However, policies with the potential to disrupt medical treatment in vulnerable populations should be carefully examined for their effect on long-term costs and patient health.

Recently, Cardinal et al cautioned about applying the results of the Antihypertensive and Lipid-Lowering Treatment To Prevent Heart Attack Trial (ALLHAT), the landmark hypertension trial, to real-world clinical settings because of the real-world patterns of poor persistence.5 Low persistence with hypertension medications is well documented.6,7 Monane et al examined persistence with hypertension medications in New Jersey Medicaid recipients and found patients initiating treatment for hypertension continued with therapy for an average of 161 days and 21% of them did not refill their initial prescription.8 Moreover, poor adherence and persistence are costly. In another study of Medicaid patients with hypertension, patients with documented nonadherence to antihypertensive therapy had total medical costs that were $873 higher per patient than those of hypertensive patients without documented nonadherence. The higher costs were primarily due to higher inpatient hospital expenditures (averaging $637 per patient).9 Another study found that 11% of hospital admissions among the elderly were due to nonadherence.10

In an effort to limit drug utilization and contain costs within state Medicaid programs, states have begun to use instruments such as preferred drug lists (PDLs) and other measures that restrict access to medicines.11 There is little doubt that prior authorization is an effective tool for reducing the use of higher cost medications. However, research is limited on the total healthcare cost effectiveness and long-term outcomes of access restrictions resulting from Medicaid PDLs. Smalley et al used a time-series approach to show that expenditures for nonsteroidal anti-inflammatory drugs (NSAIDs) declined 53% after the implementation of a Medicaid prior-authorization policy by Tennessee that encouraged patients to switch to generic medications.12 There were no associated increases in medical costs, but the study noted a significant reduction in the use of all NSAIDs. That reduction raises concerns regarding potential consequences of untreated pain for patients' quality of life, particularly as the study did not measure changes in pain and inflammation.12 Additional studies examined the effect of other drug utilization management practices. Schneeweiss et al reported that a reference pricing policy in Canada resulted in 18% of patients switching to a lower-cost angiotensin-converting enzyme (ACE) inhibitor with no associated increase in medication discontinuation; however, visits to physicians and hospitals did increase moderately in the time immediately following the switch in therapy.13 Cost sharing among the poor and elderly in Canada was shown to decrease the use of essential and nonessential drugs, but with the consequence of increasing emergency room visits by those patients who reduced their use of essential drugs.14

This study extends the existing body of evidence by examining Medicaid patients' prescription refill behavior in a state where several classes of hypertension drugs were restricted. The restrictions resulted in a higher rate of medication switching than had been observed in some of the existing analyses. Furthermore, this study examines the limitations for add-on therapy following the restrictions.

When a Medicaid PDL is implemented, the Medicaid patients already taking a medication that is not on the PDL must have their physicians request prior authorization from the Medicaid program or switch them to another medication not restricted by the PDL. All drugs are available to Medicaid recipients, but the restricted drugs have the additional hurdle of the prior-authorization process. If the physician submits the prior-authorization request and it is approved, then the patient can continue to receive full Medicaid coverage for their existing prescription. If the prior-authorization request is not approved, patients must pay for their prescription out of pocket or switch to a medication on the PDL. In certain states, patients who are already taking a restricted prescription are exempt.

In the state studied, patients taking a restricted medication at the time the PDL was implemented were allowed to refill their existing prescription until it ran out before submitting a prior-authorization request. In the study state, 3 ACE inhibitors, 8 angiotensin II receptor blockers, and 6 calcium channel blockers were restricted in mid June and early July 2002. The state imposed a PDL for high-cholesterol medications 6 months after the hypertension restrictions, so although high cholesterol also is a risk factor for cardiovascular disease, these medications are not included in this study.

Prescription treatment for hypertension is complex and may include initiation of multiple therapies, dose titration, and add-on medications. Many patients require 2 or more hypertension medicines taken concurrently to reach blood pressure goals; patients who are started on monotherapy should have another agent added from a different category of hypertension medication if sufficient blood pressure reduction is not achieved. Patients with comorbid conditions, including diabetes and chronic kidney disease, often require 2 to 3 hypertension medications to lower blood pressure to the recommended level.15 When a hypertension drug is restricted by a PDL, the patient's physician may switch to another hypertension drug of the same type that is not restricted (eg, replace a calcium channel blocker with another calcium channel blocker), or to 1 or more medications in a different category (eg, replace a calcium channel blocker with an ACE inhibitor or a beta-blocker plus a diuretic). Patients who were not on a restricted drug prior to implementation of the PDL also could be affected by the restrictions later on if a physician attempts to add a restricted medication to their regimen because their blood pressure is not sufficiently reduced.

Given the high prevalence of hypertension among patients in the Medicaid system and the consequences of discontinuing medication, as a first step this study explored the impact of Medicaid access restrictions on persistence with hypertension medications, focusing on patients taking those classes of medications that were subject to restrictions. This study sought to evaluate the following questions within the limitations of the data available in the study state:

  • Did the restriction have a measurable effect on a patient's likelihood of discontinuing therapy with hypertension medication?
  • Did the restriction have a measurable effect on the likelihood that an existing patient's medication would be switched?
  • Finally, did the restriction have a measurable effect on the likelihood that a physician would add the restricted therapy to a patient's pharmaceutical regimen?

METHODS

Data Sources

The prescription data for this study were extracted from the Verispan Inc. (Yardley, Penn) data warehouse. The Verispan database is derived from pharmacy records, prescription benefit claims, and the pharmacy switch processor. Medicaid prescription data in Verispan are drawn primarily from retail pharmacy chains, pharmacy software used by independent pharmacies to submit claims, and pharmacy switch processors. The data captured directly from the pharmacies include 100% of all transactions in the pharmacy. The full Verispan dataset includes 50% to 55% of US retail prescriptions.

The data for this study were limited to those sources for which Verispan had consistently received data since June 2000. This subset of approximately 270 pharmacies in the study state included approximately 15% of all prescriptions in the state. The prescription data included the name of the drug, the quantity supplied, the date the prescription was filled, the days of supply, the zip code of the pharmacy, and the age and sex of the patient. Verispan utilizes a unique identifier compliant with the Health Insurance Portability and Accountability Act of 1996 (HIPAA) to link patient prescription records together over time for the same patient. The data in this study include prescriptions filled between June 2000 and May 2003.

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