New prescriptions of hydroxychloroquine (HCQ) and ivermectin increased in 2020, driven particularly by rates in counties with the highest proportion of Republican votes in the 2020 US presidential election, according to a cross-sectional study published today in JAMA Internal Medicine.

“Our findings are consistent with the hypothesis that US prescribing of hydroxychloroquine and ivermectin during the COVID-19 pandemic may have been influenced by political affiliation,” wrote Michael L. Barnett, MD, of the Harvard T.H. Chan School of Public Health in Boston, Massachusetts, and colleagues.

The researchers used data from the OptumLabs Data Warehouse to analyze commercial and Medicare Advantage medical claims from January 2019 through December 2020 for more than 18.5 million adults living in counties with at least 50 enrollees.

Using US Census data and 2020 presidential election results, the researchers classified counties according to their proportion of Republican voters and then examined whether those proportions were associated with that county’s rates of new prescriptions for HCQ, ivermectin, methotrexate sodium, and albendazole. Methotrexate is prescribed for similar conditions and indications as HCQ, and albendazole is prescribed for similar reasons as ivermectin, although neither of the comparison drugs has been considered for COVID-19 treatment.

The Food and Drug Administration issued an emergency use authorization (EUA) for HCQ as a COVID-19 treatment on March 28, 2020, but the agency revoked the EUA 3 months later on June 15. Ivermectin never received an EUA for COVID treatment, but an in vitro study published April 3, 2020 claimed it had an antiviral effect.

The National Institutes of Health recommended against using ivermectin as a COVID-19 treatment on August 1, 2020, but a few months later, on November 13, a flawed clinical trial — later retracted — claimed ivermectin was 90% effective in treating COVID-19. Despite the lack of evidence for ivermectin’s efficacy, a Senate committee meeting on December 8, 2020, included testimony from a physician who promoted its use.

In comparing ivermectin and HCQ prescription rates with counties’ political composition, the researchers adjusted their findings to account for differences in the counties’ racial composition and COVID-19 incidence as well as enrollees’ age, sex, insurance type, income, comorbidity burden, and home in a rural or urban area.

The results showed an average of 20 new HCQ prescriptions per 100,000 enrollees in 2019, but 2020 saw a sharp increase and drop in new HCQ prescriptions in March-April 2020, independent of counties’ breakdown of political affiliation.

“However, after June 2020, coinciding with the revocation of the US Food and Drug Administration’s emergency use authorization for hydroxychloroquine, prescribing volume was significantly higher in the highest vs lowest Republican vote share counties,” the authors report. The gradual increase from June through December 2020 averaged to 42 new prescriptions per 100,000, a 146% increase over 2019 rates that was driven largely by the 25% of counties with the highest proportion of Republican voters.

Similarly, rates of new ivermectin prescriptions in December 2020 were more than nine times higher in counties with the highest Republican vote share, compared with new prescriptions throughout 2019. The researchers found no differences in new prescriptions for methotrexate or albendazole in 2020 based on counties’ proportion of Republican votes.

Since the study is an ecological, observational one, it cannot show causation or shed light on what role patients, physicians, or other factors might have played in prescribing patterns. Nevertheless, the authors noted the potentially negative implications of their findings.

“Because political affiliation should not be a factor in clinical treatment decisions, our findings raise concerns for public trust in a nonpartisan healthcare system,” the authors write.