Use of Peripheral μ-Opioid Receptor Antagonists for Treating Opioid-Induced Constipation among US Medicare Beneficiaries from 2014 to 2018

Background: Opioid-induced constipation (OIC) remains the most common adverse event associated with opioid use. Treatment with more novel and costly agents (such as peripheral μ-opioid receptor antagonists [PAMORAs]) may be indicated in patients with laxative-refractory OIC. Three PAMORAs are U.S. Food and Drug Administration approved for managing OIC-methylnaltrexone (FDA approved in 2008), naloxegol (in 2014), and naldemedine (in 2017). These drugs are indicated only in limited scenarios. Their contemporary patterns of use and burden of spending remain unknown. Objective: To evaluate the trends in use and expenditures for the three PAMORAs approved for treating OIC. Design: Retrospective cross-sectional study using the 2014-2018 Medicare Part D Prescription Drug Event data and the 2018 Part D Prescriber Public Use File. Setting: Prescribers and beneficiaries using PAMORAs. Measurements: The annual spending, number of beneficiaries, number of claims, and spending per beneficiary and claim for each PAMORA. The distribution by prescriber specialty using PAMORA. Results: From 2014 to 2018, aggregate spending on PAMORAs increased, from $13.6 to $150.9 million, and use increased, from 4221 to 72,592 beneficiaries. After FDA approval in 2014, naloxegol overtook methylnaltrexone in the number of users in 2015 and spending in 2016. In 2018, 6989 unique prescribers used any PAMORA. Among them, the most common specialties/professions were family practice (20.2%), internal medicine (18.0%), and nurse practitioner (15.4%). Conclusions: Our findings-significant and increasing expenditure on PAMORAs, and broad use across specialties-serve as a call for defining and implementing appropriate use of PAMORAs.