In 2014, an estimated 1.9 million Americans had prescription opioid use disorder and 0.6 million had heroin use disorder.1 Opioid overdose mortality has tripled since 2000 and reached a record high of >28,000 deaths in 2014.2 Furthermore, as legitimate channels of prescription opioids become increasingly restricted, many areas have witnessed a surge in heroin use and emergence of synthetic and nonpharmaceutical opioids manufactured in illegal laboratories (eg, illicit fentanyl).2,3 The shifting landscape of the US opioid epidemic underscores the essential role of opioid use disorder treatment in addressing the underlying addictive behavior and curbing the epidemic.4
Buprenorphine (including buprenorphine-naloxone) is the most commonly prescribed medication for opioid use disorder treatment and is effective in managing withdrawal symptoms and reducing the potential for relapse.5–7 Compared with other FDA-approved medications such as methadone and naltrexone, buprenorphine has relatively high patient retention and sustained recovery as well as low addition liability and minimum overdose risk.8,9 Furthermore, buprenorphine is the only type of medication-assisted treatment of opioid use disorder that can be prescribed outside traditional stand-alone opioid treatment programs.
Despite the safety and efficacy profiles of buprenorphine and the extension of medication-assisted treatment into mainstream medical settings, at $6000 for a full year treatment course, lack of health insurance coverage poses a barrier to buprenorphine utilization.10,11 Prior the Affordable Care Act (ACA), most low-income people in need of medication-assisted treatment were ineligible for Medicaid and left untreated.12–15 Starting in 2014, 26 states and District of Columbia expanded Medicaid eligibility to almost all low-income residents with household income at or below 138% of the federal poverty level, a group that has a disproportionately high risk of opioid use disorder and sizable unmet treatment needs.16,17 With state implementation of these Medicaid expansions, behavioral health experts and advocates expect Medicaid to play a central role in financing the utilization of buprenorphine for medication-assisted treatment.5,15,18 Our study examines how Medicaid expansion may have impacted Medicaid-covered buprenorphine prescriptions and buprenorphine spending.
A second barrier to medication-assisted treatment of opioid use disorder is system capacity for the prescribing of buprenorphine. The 2000 Drug Addiction Treatment Act (DATA) and the 2006 Office of National Drug Control Policy Reauthorization Act allow qualified office-based physicians to prescribe buprenorphine through a DATA waiver.19 Under the DATA 2000, an office-based physician who has a board certification in addiction medicine/psychiatry or completes an 8-hour course of buprenorphine prescribing training is qualified to treat up to 30 patients at a time.19 The 2006 Amendment raised the patient limit from 30 to 100 for a physician who had been authorized under the DATA 2000 for more than a year and who submitted an application conveying his/her need and certifying his/her qualifications. Previous literature documents state variations in the availability of DATA-waived physicians qualified to prescribe buprenorphine.10,20–22 Increasing physician prescribing capacity features prominently in recent federal actions to address the opioid epidemic.23 As such, our study also examines the varied capacity for buprenorphine prescribing may affect the extent to which the implementation of Medicaid expansions and the potential increases in treatment needs can translate into the meaningful improvement in buprenorphine utilization.
METHODS
Data and Sample
The primary data sources for this study are the Medicaid Drug Utilization files from the Centers for Medicare and Medicaid Services. All states are required to report to the Centers for Medicare and Medicaid Services on prescription activities of all Medicaid-covered outpatient drugs in exchange for federal matching funds.24 We derived quarterly, state aggregate prescription and spending data from over 200 official reporting files from 2011 through 2014. Washington, DC was excluded because of inconsistency in its managed care data reporting.
Each drug product in the Medicaid Drug Utilization files is identified by a National Drug Code number which we linked to the FDA Orange Book to identify buprenorphine (including the buprenorphine-naloxone formulations) for medication-assisted treatment of opioid use disorder. Please see Appendix A1 (Supplemental Digital Content, https://links.lww.com/MLR/B346) for detailed information on the identification of buprenorphine.
Study Variables
The outcome variable is Medicaid-covered buprenorphine utilization measured by quarterly Medicaid prescriptions for, and spending on, buprenorphine both on a per 1000-state resident basis and on a per 1000-Medicaid enrollee basis.
One key independent variable of interest is state implementation of Medicaid expansions under the ACA. By the end of 2014, 26 states and District of Columbia had implemented the expansions either in compliance with the ACA Medicaid State Plan Amendment provision or through the Section §1115 waiver.25 Please see Appendix A2 (Supplemental Digital Content, https://links.lww.com/MLR/B346) for a summary of the ACA Medicaid expansions.
The other independent variable of interest is physician prescribing capacity, measured as time-varying counts of 100 patient-waived physicians and 30 patient-waived physicians per 1,000,000 residents.
We included the following covariates to control for the state-level factors that may correlated with both Medicaid expansions and buprenorphine utilization: (i) unemployment rate, (ii) poverty rate, and (iii) an “early adopter” indicator for partial implementation of Medicaid expansions in 3 states between 2011 and 2013.26 Please see Appendix A3 (Supplemental Digital Content, https://links.lww.com/MLR/B346) for data sources and measurement of study variables.26
Statistical Analysis
We used a quasi experimental difference-in-differences (DD) design with state and quarter 2-way fixed effects to account for unobserved state heterogeneity and national secular trend in buprenorphine utilization that may systematically be correlated with Medicaid expansion (eg, the underlying opioid use prevalence).27 Please see Appendix A3 (Supplemental Digital Content, https://links.lww.com/MLR/B346) for model specifications of the main analysis and Appendix A4 (Supplemental Digital Content, https://links.lww.com/MLR/B346) for the statistics from “parallel trend test” of the validity of DD design. We also conducted sensitivity analyses to further account for the heterogeneous preexpansion trajectories in buprenorphine utilization between the expansion states and the nonexpansion and late-expansion states, as well as the heterogeneous policy effects among the expansion states. Please see Appendix A3 (Supplemental Digital Content 1, https://links.lww.com/MLR/B346) and A9 (Supplemental Digital Content, https://links.lww.com/MLR/B346) for model specifications of the sensitivity analyses. All estimates were population-weighted and state-clustered to correct for heterogeneous policy effect and within-state serial correlation.28
RESULTS
Temporal Trends in Medicaid-covered Buprenorphine Utilization
Figures 1 and 2 show the trends in Medicaid-covered buprenorphine utilization from the preexpansion period (2011–2013) to the postexpansion period (2014). We observed upward trends in Medicaid-covered buprenorphine prescriptions (Fig. 1) and buprenorphine spending (Fig. 2) in the 26 states that implemented Medicaid expansions in 2014 but not in the nonexpansion and late-expansion states. The trend comparison suggests that the observed prescription growth and spending growth may have partially been attributed to the Medicaid expansions.
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FIGURE 1: Temporal trends in total Medicaid prescriptions for buprenorphine for medication-assisted treatment. Source: Authors’ analysis of the CMS Medicaid Drug Utilization Files 2011–2014.
FIGURE 2: Temporal trends in total Medicaid spending on buprenorphine for medication-assisted treatment. Source: Authors’ analysis of the CMS Medicaid Drug Utilization Files 2011–2014.
Estimated Effects of Medicaid Expansions and Physician Prescribing Capacity on Medicaid-covered Buprenorphine Prescriptions
Table 1 presents the DD estimates for the effect of Medicaid expansion on Medicaid-covered buprenorphine prescriptions.
TABLE 1: Effects of Medicaid Expansion and Physician Prescribing Capacity on Medicaid Prescriptions for Buprenorphine
Regarding the per 1000 resident buprenorphine prescriptions (Table 1), we found a pre-post increase of 1.30 prescriptions per 1000 residents per quarter in the expansion states [row 2, column 3: 95% confidence interval (CI), 0.72–1.89], which was significantly larger than the nonexpansion and late-expansion states. After adjusting for the state and quarter 2-way fixed effects, as well as the state-level availability of DATA-waived physicians and other covariates, our DD estimate indicates that state implementation of Medicaid expansions in 2014 was associated with an increase in Medicaid-covered buprenorphine prescriptions by 0.69 per 1000 residents per quarter (row 2, column 5: 95% CI, 0.14–1.24). The national average numbers of 100 patient-waived Medicaid-covered buprenorphine prescriptions was 0.99 per 1000 residents per quarter, thus the estimated 0.69 per 1000 residents per quarter increase represents a relative 69.7% increase in Medicaid prescriptions for buprenorphine associated with the implementation of Medicaid expansions.
We also found that every additional 100 patient-waived physician per 1,000,000 residents was associated with an increase in Medicaid-covered buprenorphine prescriptions by 0.20 per 1000 residents per quarter (row 3, column 5: 95% CI, 0.15–0.26), or a relative 20.2%. Given that the national average numbers of 100 patient-waived physicians was 22.34 per 1,000,000 residents, our estimate implies that a 10% increase (ie, 2.234 per 1,000,000 residents) in the number of 100 patient-waived physicians was associated with a 45.1% increase in buprenorphine prescriptions (20.2%×2.234). Changes in the availability of 30 patient-waived physicians, on the other hand, did not have a statistically discernable effect on Medicaid-covered buprenorphine prescriptions.
Estimated Effects of Medicaid Expansions and Physician Prescribing Capacity on Medicaid-covered Buprenorphine Spending
In addition to the estimated increases in buprenorphine prescriptions, we also found similar patterns in Medicaid spending on buprenorphine (Table 2). Compared with the pre-post spending growth in the nonexpansion and late-expansion states, the expansion states saw a higher growth in Medicaid buprenorphine spending (row 2, columns 5: $117.5; 95% CI, 23.1–211.9). Translating the absolute effect sizes into percentage changes, state implementation of Medicaid expansions in 2014 was associated with a 49.9% growth in Medicaid buprenorphine spending on a per 1000 resident basis, or total Medicaid spending on buprenorphine.
TABLE 2: Effects of Medicaid Expansion and Physician Prescribing Capacity on Medicaid Spending on Buprenorphine
Furthermore, we found that every additional 100 patient-waived physician per 1,000,000 residents was associated with a spending growth of $33.1 per 1000 residents per quarter (row 3, columns 5: 95% CI, 22.6–43.7), or a relative 14.0%. Our estimate implies that a 10% increase in the availability of 100 patient-waived physicians associated with a 31.3% increase in buprenorphine spending on a per 1000 resident basis (14.0%×2.234). We also found a spending growth of $12.1 per 1000 residents per quarter (row 4, columns 5: 95% CI, −0.8 to 25.2) attributable to every additional 30 patient-waived physician per 1,000,000 residents, albeit only significant at the 0.10 level.
DISCUSSION
Our findings provide some of the first empirical evidence concerning the impact of Medicaid expansions under the ACA on the utilization of buprenorphine for medication-assisted treatment of opioid use disorder. We found that state implementation of the expansions was associated with a 70% increase in Medicaid-covered buprenorphine prescriptions, and a 50% increase in Medicaid spending on buprenorphine. The main findings were consistent with those from sensitivity analyses (please see Appendix Tables A7–A9, Supplemental Digital Content, https://links.lww.com/MLR/B346, for the sensitivity analysis results). Similar early effects of the ACA Medicaid expansions on access to substance use disorder treatment have been observed in Medicaid claims data in states such as Kentucky and experienced by physicians in Massachusetts and Maryland.29–31 As many expansion states such as Kentucky, New Hampshire, and New York start to implement legislative initiatives to facilitate access to Medicaid coverage and medication-assisted treatment among low-income people with opioid use disorder,32–35 we expect to see even more significant improvement in buprenorphine utilization in the future.
Our findings also suggest that the availability of DATA-waived physicians, particularly the 100 patient-waived physicians, is also associated with increases in Medicaid-covered buprenorphine prescriptions and spending. It is worth noting that including the availability of DATA-waived physicians into the main analyses reduced the effects of the ACA Medicaid expansions on buprenorphine prescriptions and buprenorphine spending by 38.9% (Appendix A5, Supplemental Digital Content, https://links.lww.com/MLR/B346, row 2: from 1.13 to 0.69 per 1000 residents per quarter) and 30.9% (Appendix A6, Supplemental Digital Content, https://links.lww.com/MLR/B346, row 2: from $167.5 to $117.5 per 1000 residents per quarter). These findings suggest that limited physician prescribing capacity may impose a constraint on the policy impact of Medicaid expansions. In other words, sufficient physician prescribing capacity is necessary for ensuring that Medicaid expansion achieves its full potential in improving buprenorphine utilization. On July 6, 2016, the Department of Health and Human Services released a final rule, effective on August 8, 2016, to raise the patient limit from 100 to 275 for DATA-waived physicians.36 As new enrollees in the expansion states may present Medicaid and healthcare system with additional needs for medication-assisted treatment, active physician participation in the provision of buprenorphine, coupled with an enabling policy environment, will help absorb the potential increase in treatment needs and address the ongoing opioid epidemic. Future research is needed to explore this interaction policy effect of physician prescribing capacity and Medicaid expansions on improving treatment access and reducing opioid use disorder.
In conclusion, our study uses timely, comprehensive Medicaid administrative data and provides some of the first empirical evidence that state implementation of Medicaid expansions may have significantly increased Medicaid-covered buprenorphine prescriptions and buprenorphine spending. Our findings suggest that Medicaid expansion has the potential to reduce the financial barriers to buprenorphine utilization and improve access to medication-assisted treatment of opioid use disorder. In this regard, physicians and policymakers should be mindful of the additional needs for medication-assisted treatment associated with Medicaid expansions and create a supportive environment to translate the potential increase in treatment needs into the meaningful improvement in buprenorphine utilization, which will be crucial in addressing the nation’s opioid epidemic.
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