Concerns about the advances of the COVID-19 epidemic have sparked many debates around the world. One such discussion revolved around the use of the drug called chloroquine, initially thought to be effective in reducing the mortality rate of the infection. Particularly in Brazil, even after new studies pointed to the drug's ineffectiveness, the federal government kept the recommendation of this drug as an official treatment. The publication of an official authorization of the use of chloroquine on Twitter sparked an intense debate on social media with arguments against and in favor. This paper studies the dynamics of interactions among different user groups around this discussion, relying on network science and topic modeling analyses. Our results highlight two distinct behaviors in Twitter interaction networks, where retweets serve as positive reinforcements within information bubbles and replies act as a space of direct debate. Also, discussions are seeded by public figures, but regular users carry on the debate per se. The topic modeling analyses revealed three observable user groups in this debate: strong supporters of the Brazilian government, progressive opposition to this government, and moderate users that oppose to this specific topic but do not reject the government agenda as a whole. © 2021 IEEE Computer Society. All rights reserved.