page_title: COVID-19 drug repurposing research
section_title: Chloroquine and hydroxychloroquine
hierarchical_section_title: COVID-19 drug repurposing research / Studies / Chloroquine and hydroxychloroquine
caption_attribution_description: English: Free public domain stock photo of medicine container and medicine tablet
context_page_description: Drug repositioning is the re-purposing of an approved drug for the treatment of a different disease or medical condition than that for which it was originally developed. This is one line of scientific research which is being pursued to develop safe and effective COVID-19 treatments. Other research directions include the development of a COVID-19 vaccine and convalescent plasma transfusion.
  Several existing antiviral medications, previously developed or used as treatments for severe acute respiratory syndrome, Middle East respiratory syndrome, HIV/AIDS, and malaria, have been researched as COVID‑19 treatments, with some moving into clinical trials.
  In a statement to the journal Nature Biotechnology in February 2020, US National Institutes of Health Viral Ecology Unit chief Vincent Munster said, "The general genomic layout and the general replication kinetics and the biology of the MERS, SARS and [SARS-CoV-2] viruses are very similar, so testing drugs which target relatively generic parts of these coronaviruses is a logical step".
context_section_description: Chloroquine is an anti-malarial medication also used against some auto-immune diseases. On 18 March, the World Health Organization (WHO) announced that chloroquine and the related hydroxychloroquine would be among the four drugs studied as part of the multinational Solidarity clinical trial. On 19 March, US President Donald Trump encouraged the use of chloroquine and hydroxychloroquine during a national press conference. These endorsements led to massive increases in public demand for the drugs in the United States. New York Governor Andrew Cuomo announced that New York State trials of chloroquine and hydroxychloroquine would begin on 24 March.
  On 28 March, the US Food and Drug Administration (FDA) authorized the use of hydroxychloroquine sulfate and chloroquine phosphate under an Emergency Use Authorization (EUA). The treatment has not been approved by the FDA's clinical trials process. However, the drug is authorized under the EUA as an experimental treatment for emergency use in patients who are hospitalized, but are not able to receive treatment in a clinical trial. The Centers for Disease Control and Prevention (CDC) said that "the use, dosing, or duration of hydroxychloroquine for prophylaxis or treatment of SARS-CoV-2 infection" are not yet established. Doctors have said they are using the drug when "there's no other option". On 9 April, the National Institutes of Health began the first clinical trial to assess whether hydroxychloroquine is safe and effective to treat COVID‑19.
  On 15 June, the FDA revoked the emergency use authorization for hydroxychloroquine and chloroquine, stating that although the evaluation of both these drugs under clinical trials continues, the FDA (after interagency consultation with the Biomedical Advanced Research and Development Authority (BARDA)) concluded that, based on new information and other information discussed "... it is no longer reasonable to believe that oral formulations of hydroxychloroquine (HCQ) and chloroquine (CQ) may be effective in treating COVID‑19, nor is it reasonable to believe that the known and potential benefits of these products outweigh their known and potential risks".
  On 24 April, the FDA cautioned against using the drug outside a hospital setting or clinical trial after reviewing case reports of adverse effects including ventricular tachycardia, ventricular fibrillation and in some cases death. According to Johns Hopkins' ABX Guide for COVID‑19, "Hydroxychloroquine may cause prolonged QT, and caution should be used in critically ill COVID‑19 patients who may have cardiac dysfunction or if combined with other drugs that cause QT prolongation". Caution was also recommended as to the combination of chloroquine and hydroxychloroquine with treatments which might inhibit the CYP3A4 enzyme (by which these drugs are metabolized). As such, combination might indirectly result in higher plasma levels of chloroquine and hydroxychloroquine, and thus enhance the risk for significant QT prolongation. CYP3A4 inhibitors include Azithromycin, ritonavir and lopinavir. A Veterans Affairs study released results on 21 April suggesting COVID‑19-hospitalized patients treated with hydroxychloroquine were more likely to die than those who received no drug treatment at all, after correcting for clinical characteristics.
  A randomized, double-blind, placebo-controlled trial of hydroxychloroquine in 821 participants by the University of Minnesota Medical School found that it does not treat COVID‑19 infection.
  In June, use of hydroxychloroquine in the UK RECOVERY Trial was discontinued when an interim analysis of 1,542 treatments showed it provided no mortality benefit to people hospitalized with severe COVID‑19 infection over 28 days of observation.
  A multicenter, randomized, open-label, three-group, controlled trial of 667 participants in Brazil found no benefit from using hydroxychloroquine, alone or with azithromycin, to treat mild-to-moderate COVID‑19.
  In late July, the U.S President Donald Trump once again promoted the use of the drug contradicting various public health officials
caption: A chloroquine tablet
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