The medication chloroquine has been in the news recently as a possible treatment for the coronavirus disease, COVID-19.  Known primarily for nearly 90 years as way to prevent and treat malaria, chloroquine is also occasionally used for lupus and rheumatoid arthritis.

Chloroquine was discovered in 1934 by Hans Andersag (1902-1955), a chemist working for the German pharmaceutical company Bayer AG.  The drug ­­ — generally well tolerated and inexpensive –­­ is on the World Health Organization’s List of Essential Medicines and regarded as the safest and most effective medicines needed in a health system.

Chloroquine is a chemical analogue of the quinoline antimalarial drug, quinine…which was isolated from the bark of the Cinchona tree (Cinchona officinalis), a traditional remedy used for centuries by indigenous people in Peru to fight chills and fever.

The drug’s safe and effective use in treating the coronavirus, however, is unclear.  The use of chloroquine raises several health concerns that have been expressed:

The evidence of chloroquine’s effectiveness is still unknown.  Chinese data about its efficacy is scant, based on a study of monkey cells in test tubes and a consensus report from doctors in one province.  A French study compared 20 patients who took the drug to 16 who didn’t.  However, the medication is being utilized, and the anecdotal information is promising.

The drug has side effects.  Side effects include blurred vision, nausea, vomiting, abdominal cramps, headache, diarrhea, swelling legs/ankles, shortness of breath, pale lips/nails/skin, muscle weakness, easy bruising/bleeding, hearing and mental problems.  Clinical epidemiologist Peter Jüni of the University of Toronto  was quoted recently as saying, “If you just have millions of people taking a drug with known toxicities, haphazardly, we are going to see major safety problems.”

There might be shortages for people who need it.  Arthritis and lupus patients quickly reported a run on pharmacy stocks of the drug.

The rush for the drug might interfere with efforts to test it in clinical trials.  Taking unproven drugs might interfere with efforts to test them to find out if they really work.  “It’s the trials that will tell us what’s going on,” said Dr. Jüni, adding that it is impossible to evaluate the drug effectively “based on evidence that is just incomplete and invalid, whether it works or not.”

False drug hopes might inhibit the effectiveness of social distancing.  It takes weeks for social distancing to start impacting new case numbers since, even after the numbers drop, people are still becoming infected and adding to case counts.

Nevertheless, attention is focused on chloroquine as a tool to fight the coronavirus.  In late January 2020, Chinese medical researchers reported that exploratory research into chloroquine seemed to have “fairly good inhibitory effects” on the SARS-CoV-2 virus, and requests to start clinical testing were submitted.   In addition to China, health authorities in Italy and South Korea have approved the use of chloroquine for the experimental treatment of COVID-19, noting contraindications for people with heart disease or diabetes.

In the U.S., the FDA authorized the use of hydroxychloroquine and chloroquine under an Emergency Use Authorization on March 28, 2020.  This experimental treatment has not been approved by the FDA, but rather is authorized only for emergency use for people who are hospitalized but not able to receive treatment in a clinical trial.  A few days later on April 1, 2020, the European Medicines Agency issued guidance that chloroquine and hydroxychloroquine are only to be used in clinical trials or emergency use programs.