Chloroquine, A Common Anti-Malarial Drug, May Be a Treatment for COVID-19 – Beware of Drug Interactions!

March 21, 2020

From Ahvie Herskowitz, MD and Devin Wilson, ND

As the COVID-19 pandemic continues researchers from all over the world scramble to find safe and effective treatment options. Although there are many therapies being considered there is no vaccine or treatment approved for use at this time.

However, in February 2020, the National Health and Care Commission of China officially declared chloroquine, a drug that has been used for malaria for over 50 years, as a medical agent for COVID-19 in the newest edition of the new coronavirus pneumonia diagnosis and treatment plan.

Chloroquine was investigated for its anti-viral and immune modulating properties in response to the 2003 SARS outbreak. In vitro studies (1, 2) demonstrated that chloroquine was active against SARS-CoV and other coronaviruses and exhibited anti-inflammatory properties as well. Unfortunately, this did not spark animal and human trials to be conducted at this time.

Just recently, an in vitro study showed that chloroquine effectively inhibited the SARS-CoV-2 virus. A separate in vitro study confirmed this and found that its cousin, hydroxychloroquine, was even more potent for inhibiting SARS-CoV-2.

Due to its anti-viral and immune modulating properties a number of human clinical trials investigating chloroquine for the treatment of COVID-19 patients are now underway.

  • Efficacy and Safety of Hydroxychloroquine for Treatment of Pneumonia Caused by 2019-nCoV ( HC-nCoV )
  • A prospective cohort study for the efficacy and safety of chloroquine in hospitalized patients with novel coronavirus pneumonia (COVID-19)
    Therapeutic effect of hydroxychloroquine on novel coronavirus pneumonia (COVID-19)
  • A prospective, open-label, multiple-center study for the efficacy of chloroquine phosphate in patients with novel coronavirus pneumonia (COVID-19)
  • Efficacy of Chloroquine and Lopinavir/ Ritonavir in mild/general novel coronavirus (CoVID-19) infections: a prospective, open-label, multicenter randomized controlled clinical study
  • Efficacy of therapeutic effects of hydroxycholoroquine in novel coronavirus pneumonia (COVID-19) patients(randomized open-label control clinical trial)
  • A randomized, double-blind, parallel, controlled trial for comparison of phosphoric chloroquine combined with standard therapy and standard therapy in serious/critically ill patients with novel coronavirus pneumonia (COVID-19)
  • Hydroxychloroquine treating novel coronavirus pneumonia (COVID-19): a multicenter, randomized controlled trial
  • A randomized, double-blind, parallel, controlled trial for comparison of phosphoric chloroquine combined with standard therapy and standard therapy in mild/common patients with novel coronavirus pneumonia (COVID-19)
  • A Single-blind, Randomized, Controlled Clinical Trial for Chloroquine Phosphate in the treatment of Novel Coronavirus Pneumonia 2019 (COVID-19)
  • A Single-arm Clinical Trial for Chloroquine Phosphate in the treatment of Novel Coronavirus Pneumonia 2019 (COVID-19)
  • A prospective, randomized, open-label, controlled clinical study to evaluate the preventive effect of hydroxychloroquine on close contacts after exposure to the Novel Coronavirus Pneumonia (COVID-19)

Is Chloroquine the answer for preventing and treating COVID-19?

Although promising, the safety and efficacy of chloroquine in COVID-19 has not yet been established in human clinical trials. Optimal dosing strategies have also not been studied. Considering this, chloroquine may be a promising treatment and gives us hope that an old drug may be a significant tool to defend us from the virus.

Even if chloroquine becomes widely recommended for the treatment or prevention of COVID-19, not all people will be able to take it, as it has specific cardiovascular risks, interacts with many drugs and has various side effects. Below, is a long list of considerations for practitioners and patients alike to become familiar with.

Cardiovascular Risks of Chloroquine

  • Although rare, chloroquine has been associated with potentially dangerous cardiac side effects including ventricular arrhythmias, QT prolongation, QRS complex widening and torsades de pointes all of which can be life threatening. Cases of cardiomyopathy resulting in heart failure have also been reported in patients on long term chloroquine therapy at high doses. Deaths following chloroquine overdose and long term treatment of conditions other than malaria have been reported.
  • Due to chloroquine’s effect on the electrical conduction of the heart, caution must be used in patients with previous cardiac disease, history of arrhythmias, low heart rate, low potassium, low magnesium, and use of drugs that can cause QT prolongation such as Ondansetron (Zofran).
  • Apart from other anti-malarial medications such as halofantrine, chloroquine has been used extensively with an overall low risk of cardiotoxicity when used short term at recommended doses.

Other risks of Chloroquine

  • Chloroquine should not be taken by people with a hypersensitivity to chloroquine or those with psoriasis, porphyria, and retinal or vision changes.
  • Chloroquine has been shown to cause severe low blood sugar including loss of consciousness that could be life threatening in all patients but specifically those taking anti-diabetic medications.
  • Chloroquine may cause destruction of red blood cells (hemolysis) in patients with glucose-6phosphate dehydrogenase deficiency (G6PD) or patients on other drugs known to cause hemolysis.
  • It may also exacerbate underlying liver conditions, provoke seizures in patients with a history of epilepsy and cause irreversible damage to the retina when used long term.
  • Although there are no adequate studies evaluating the safety of chloroquine in pregnant women, it is recommended that usage be avoided except in prophylaxis or treatment of malaria when benefits out weight potential risk to the fetus.

Chloroquine interacts with many drugs

  • Being aware of specific drug interactions is critical for ensuring safety as there can be dangerous interactions that increase side effects and or the risk of death.
  • Chloroquine interacts with a large number of drugs, all with different levels of risk and considerations for management. For example, chloroquine may enhance the risk of arrhythmias associated with Ondansetron, also known as Zofran, a common anti-nausea medication. Cimetidine, a common medication for indigestion, can inhibit chloroquine metabolism, increasing it to potentially dangerous levels in the blood.
  • Considering the long list of drugs that chloroquine interacts with it cannot simply be recommended to every patient for the purpose of preventing or treating COVID-19.
  • Check with your doctor before starting any new medication or supplement to ensure it is safe for you to take.
  • A full list of drugs that chloroquine interacts with can be found here.

Common side effects of chloroquine

Like many medications, chloroquine is associated with various sides effects including the ones listed below. The most common reported side effects are gastrointestinal, and include vomiting and diarrhea:

  • Abdominal pain
  • Abdominal cramps
  • Lack of appetite
  • Nausea
  • Vomitting
  • Headache
  • Diarrhea
  • Skin discoloration
  • Hair discoloration
  • Hair loss.

Although past and present data is promising, and chloroquine has already been recommended by various governmental authorities in China, the safety and efficacy in COVID-19 hasve not yet been established in human clinical trials. Considering this, chloroquine may be a promising treatment, but we may have to wait for more clinical data to emerge in order to provide safe and specific recommendations.


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About Ahvie Herskowitz, MD

Dr. Herskowitz’s extensive training includes a medical degree from The Albert Einstein College of Medicine, residencies in Anatomic Pathology and Internal Medicine, and Fellowship training in Cardiology at The Johns Hopkins Medical Center. During his 12 years at Johns Hopkins, he became Associate Professor of Medicine and Immunology and Molecular Microbiology and led a research team in the study of molecular and immunological mechanisms of inflammation, autoimmunity, ischemia, heart transplantation rejection and congestive heart failure.

Dr. Herskowitz’s latest academic appointment was as Clinical Professor of Medicine at UC San Francisco. To learn more about Dr. Herskowitz, you can read it bio here.


About Devin Wilson, ND

Dr. Devin Wilson is a licensed Naturopathic Doctor in the state of California. He treats an array of acute and chronic diseases using a holistic and integrative approach to health. Dr. Wilson is also a health consultant, researcher and writer focusing on anti-aging and longevity medicine.

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