What Are Chloroquine and Hydroxychloroquine and Can They Be Used to Treat COVID-19?

As the number of newly diagnosed cases of COVID-19 disease accelerates around the world, researchers, health care workers, and patients are all searching for ways to treat the illness, or at least lessen its impact.

On March 28, 2020, the FDA issued an “Emergency Use Authorization” for two medications that may have a role in managing COVID-19. These medications are hydroxychloroquine sulfate and chloroquine phosphate. Both have been used previously in patients with other medical conditions, and they are both currently available in the U.S. market.

What exactly are chloroquine and hydroxychloroquine, and what is known about their ability to help in the battle against COVID-19? Read on to learn more.

What Is Chloroquine Phosphate?

Chloroquine phosphate is a medication that has historically been used for the treatment of malaria. It has also been used off-label as a medication to treat amoebic diseases. Chloroquine has been prescribed to patients for more than 70 years, so its effect on humans is well understood by clinicians. It is a medication that is taken orally.

What Is Hydroxychloroquine Sulfate?

Hydroxychloroquine sulfate, also known by the brand name, Plaquenil, is a medication that has traditionally been used to treat conditions such as lupus, malaria, and rheumatoid arthritis, as well as other rheumatologic diseases. It is a newer version of chloroquine that has a better safety profile and fewer interactions with other prescription drugs. It is also available in oral tablet form.

How Might These Medications Be Useful in Treating COVID-19?

Both chloroquine and hydroxychloroquine have been studied in vitro, meaning that researchers have analyzed how they perform against viruses in a laboratory setting.  A study published this month in the journal Cell Discovery showed that both medications can inhibit, or stop, growth of the SARS-CoV-2 virus, which is the virus responsible for the COVID-19 disease.

The U.S. Centers for Disease Control and Prevention (CDC) has validated these findings, stating in a COVID-19 treatment guide that both medications have been shown to have benefit against the SARS-CoV-2 virus. Per the CDC, hydroxychloroquine has shown more potent activity against the specific SARS-CoV-2 coronavirus. Hydroxychloroquine is also more widely available in the United States, so it may ultimately be a bigger player when it comes to treatment in this country.

What Is Known about the Effectiveness of Hydroxychloroquine and Chloroquine?

Only a small amount of information is currently available about the effect of these medications when it comes to treating the novel coronavirus in humans.

A small study in China showed that patients who received chloroquine or hydroxychloroquine had a reduced progression of COVID-19-related pneumonia disease and a shortening of their illness, when compared with those who did not receive the medications. It was proposed by study researchers that both hydroxychloroquine and chloroquine are useful against COVID-19 infection because of their anti-inflammatory properties and because they interfere with the ability of the SARS-CoV-2 virus to bind to cell receptors. They also interfere with other processes necessary for viral replication.

A small study in France showed that patients who received hydroxychloroquine, combined with the antibiotic azithromycin, had viral loads that were undetectable after six days, indicating a “virologic cure.”

More information, in the form of double-blind, randomized controlled trials, is still necessary in order to know the true effectiveness of these medications in treating COVID-19 disease in humans.

What Are the Risks of Using Chloroquine or Hydroxychloroquine?

Like every medication, side effects are associated with taking chloroquine and hydroxychloroquine. These medications should be used very cautiously in patients who have cardiovascular disease, particularly heart conditions that prolong the heart’s electrical activity. The use of both hydroxychloroquine and chloroquine has been associated with the development of an eye condition known as macular retinopathy. Hydroxychloroquine and chloroquine use can also cause low blood sugar levels, even in nondiabetic patients.

Can Chloroquine or Hydroxychloroquine Be Used to Prevent COVID-19 Infections?

The use of hydroxychloroquine for pre-exposure or postexposure prophylaxis in the setting of COVID-19 disease (meaning, as a treatment to prevent contraction of the virus before or after you have been exposed) is currently being permitted by the FDA, though data on its effect for this use is extremely limited.

What Research Is Being Done to Learn More?

A clinical trial being conducted by researchers at the University of Washington and New York University is investigating whether hydroxychloroquine can help to prevent the development of COVID-19 infection after a person has been exposed to the virus.

A similar clinical trial at the University of Minnesota is currently underway to examine whether hydroxychloroquine can prevent the development of illness after a coronavirus exposure and whether it can also prevent the progression of known COVID-19 disease, decreasing the risk of hospitalization for those who are infected.

Hydroxychloroquine is currently being studied in many other clinical trials worldwide, so more information will soon be available regarding this medication and its usefulness in regard to the novel coronavirus.