Assessment of Use of Combined Dextromethorphan and Quinidine in Patients With Dementia or Parkinson Disease After US Food and Drug Administration Approval for Pseudobulbar Affect.

Importance: In 2010, the US Food and Drug Administration (FDA) approved a combination of dextromethorphan hydrobromide and quinidine sulfate for the treatment of pseudobulbar affect after studies in patients with amyotrophic lateral sclerosis (ALS) or multiple sclerosis (MS). This medication, however, may be commonly prescribed in patients with dementia and/or Parkinson disease (PD). Objective: To investigate the prescribing patterns of dextromethorphan-quinidine, including trends in associated costs. Design, Setting, and Participants: This population-based cohort study of patients prescribed dextromethorphan-quinidine used data from 2 commercial insurance databases, Optum Clinformatics Data Mart and Truven Health MarketScan. The Medicare Part D Prescription Drug Program data set was used to evaluate numbers of prescriptions and total reported spending by the Centers for Medicare & Medicaid Services. Patients were included if they were prescribed dextromethorphan-quinidine from October 29, 2010, when the drug was approved, through March 1, 2017, for Optum and December 31, 2015, for Truven. Data were analyzed from December 1, 2017, through August 1, 2018. Main Outcomes and Measures: The proportion of patients prescribed dextromethorphan-quinidine with a diagnosis of MS, ALS, or dementia and/or PD, as well as the number of patients with a history of heart failure (a contraindication for the drug). Results: In the commercial health care databases, 12 858 patients filled a prescription for dextromethorphan-quinidine during the study period. Mean (SD) age was 66.0 (18.5) years, 66.7% were women, and 13.3% had a history of heart failure. Combining results from both databases, few patients had a diagnosis of MS (8.4%) or ALS (6.8%); most (57.0%) had a diagnosis of dementia and/or PD. In the Medicare Part D database, the number of patients prescribed dextromethorphan-quinidine increased 15.3-fold, from 3296 in 2011 to 50 402 in 2016. Reported spending by Centers for Medicare & Medicaid Services on this medication increased from $3.9 million in 2011 to $200.4 million in 2016. Conclusions and Relevance: Despite approval by the FDA for pseudobulbar affect based on studies of patients with ALS or MS, dextromethorphan-quinidine appears to be primarily prescribed for patients with dementia and/or PD.