Importance: In 2010, the US Food and Drug Administration approved a combination of dextromethorphan hydrobromide and quinidine sulfate with an Orphan Drug Act designation for the treatment of pseudobulbar affect in patients with amyotrophic lateral sclerosis (ALS) or multiple sclerosis (MS). This medication, however, is commonly prescribed off-label for behavioral symptoms in patients with dementia and/or Parkinson disease (PD).
Objective: To investigate the prescribing patterns of dextromethorphan-quinidine, including off-label prescribing, and 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. The Medicare Part D Prescription Drug Program data set was used to evaluate prescription number and total 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.
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; 67.0% 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 approximately 12-fold, from 3296 in 2011 to 40 448 in 2015. Centers for Medicare & Medicaid Services spending on this medication increased from $4.3 million in 2011 to $137.5 million by 2015.
Conclusions and Relevance: Despite approval by the US Food and Drug Administration as an orphan-designated drug for pseudobulbar affect related to ALS or MS, this study suggests that dextromethorphan-quinidine appears to be primarily prescribed off-label for patients with dementia and/or PD.