Hydroxychloroquine for COVID-19: Variation in Regional Political Preferences Predicted New Prescriptions after President Trump's Endorsement.

Context: On March 19, 2020, President Donald Trump endorsed using hydroxychloroquine for COVID-19 treatment despite inconclusive evidence of the drug's effectiveness. This study sought to understand the influence of political preferences on prescription uptake by quantifying the relationship between a geographic area's partisan leaning and hydroxychloroquine prescription rates following Trump's endorsement.

Methods: We analyzed hydroxychloroquine prescriptions filled in 205 continental US designated market areas (DMAs) between March 1, 2018, and July 31, 2020, and the percentage of votes for Donald Trump in the 2016 presidential election in each DMA. We estimated associations by using an empirical strategy resembling a difference-in-differences estimation.

Findings: Before President Trump's endorsement, mean weekly hydroxychloroquine prescription rates were similar across DMAs with the highest and lowest Trump vote percentages (0.56 and 0.49 scripts per 100,000). After Trump's endorsement, although both high- and low-Trump-supportive DMAs experienced sharp increases in weekly hydroxychloroquine prescription rates, results indicated a 1-percentage-point increase in share of Trump votes was associated with 0.013, or 2%, more weekly hydroxychloroquine prescriptions per 100,000 people (b = 0.013, t = 2.20, p = .028).

Conclusion: President Trump's endorsement of an untested therapy influenced prescribing behavior, especially when that endorsement aligned with communities' political leanings.