form, 200 mg is equal to 155 mg of the pure form. brand names of hydroxychloroquine include plaquenil, hydroquin, axemal (in india), dolquine, quensyl, and quinoric. covid-19 this section is an excerpt from chloroquine and hydroxychloroquine during the covid-19 pandemic. a world health organization infographic that states that hydroxychloroquine does not prevent illness or death from covid-19. chloroquine and hydroxychloroquine are anti-malarial medications also used against some auto-immune diseases. chloroquine, along with hydroxychloroquine, was an early experimental treatment for covid-19. neither drug prevents sars-cov-2 infection. cleavage of the sars-cov-2 s2 spike protein required for viral entry into cells can be accomplished by proteases tmprss2 located on the cell membrane, or by cathepsins (primarily cathepsin l) in endolysosomes. hydroxychloroquine inhibits the action of cathepsin l in endolysosomes, but because cathepsin l cleavage is minor compared to tmprss2 cleavage, hydroxychloroquine does little to inhibit sars-cov-2 infection. several countries initially used chloroquine or hydroxychloroquine for treatment of persons hospitalized with covid-19 (as of march 2020), though the drug was not formally approved through clinical trials. from april to june 2020, there was an emergency use authorization for their use in the united states, and was used off label for potential treatment of the disease. on 24 april 2020, citing the risk of "serious heart rhythm problems", the fda posted a caution against using the drug for covid-19 "outside of the hospital setting or a clinical trial". their use was withdrawn as a possible treatment for covid-19 infection when it proved to have no benefit for hospitalized patients with severe covid-19 illness in the international solidarity trial and uk recovery trial. on 15 june 2020, the fda revoked its emergency use authorization, stating that it was "no longer reasonable to believe" that the drug was effective against covid-19 or that its benefits outweighed "known and potential risks". in fall of 2020, the national institutes of health issued treatment guidelines recommending against the use of hydroxychloroquine for covid-19 except as part of a clinical trial. in 2021, hydroxychloroquine was part of the recommended treatment for mild cases in india. in 2020, the speculative use of hydroxychloroquine for covid-19 threatened its availability for people with established indications (malaria and auto-immune diseases).