Background: Chloroquine (CQ) and hydroxychloroquine (HCQ) are old drugs used against
malaria, rheumatism, inflammation in the joints, lupus, among others. These drugs showed
positive results in preliminary scientific research for treatment of the severe acute respiratory
syndrome coronavirus (SARS-CoV-2). Since the studies with CQ and HCQ are initial with small
patient populations, it is not yet known whether there are adverse effects from the use of CQ and
HCQ for patients infected with the coronavirus.
Objectives: The aim of this study was to evaluate the evidence regarding the efficacy and safety
of CQ and HCQ used against viral infection caused by SARS-CoV-2.
Study Design: This is a narrative review of the traditional prescriptions of CQ and HCQ efficacy
and adverse effects as well as their employment for coronavirus disease 2019 (COVID-19).
Setting: In vitro and clinical studies comparing the antiviral efficacy and adverse effect profile of
CQ and HCQ against COVID-19 in adult patients were evaluated.
Methods: A systemic search of reviews, including in vitro and clinical trial studies in English focusing
on CQ and HCQ effects and adverse effects against COVID-19 in the adult patient population from
PubMed was performed. It included studies reporting chloroquine and hydroxychloroquine effects
and adverse effects against COVID-19.
Results: A total of 42 articles published between 2004 and April 2020 were reviewed for
therapeutic use of CQ and HCQ. Both these drugs showed a significant in vitro potential against
coronavirus. Many studies for clinical use of CQ and HCQ showed that patients presented adverse
reactions on high doses.
Limitations: Clinical studies have some methodology shortcomings, such as lack of information
about the treatment and small number of experimental patients, leading to a misinterpretation of
the data. Besides, there are few clinical studies with a limited sample size. Moreover, most of them
did not present control groups, and some patients had died during these protocols.
Discussion: Despite both CQ and HCQ in vitro antiviral evidence, clinically, both drugs, either
alone or combined with other medications, may increase the risk of cardiac arrhythmias, leading
to cardiac arrest and sudden death. Besides, a lot of uncertainty still remains, such as starting
administration period, dose prescribed, length of treatment, patients’ condition, concomitant drug
use, among others.
Conclusion: From the studies reviewed, it is not possible to state the precise efficacy and safety
of CQ and HCQ use in the treatment of COVID-19 at any time in the course of the disease. Future
studies are warranted.
Key words: SARS-CoV-2; COVID-19; chloroquine; hydroxychloroquine; pandemic; coronavirus;
adverse effects; side effects; cardiac arrhythmias; ocular toxicity, retinopathy; pharmacokinetic.
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