Last Updated on June 16, 2020 by Douglas C. Goldberg, MD

Antimalarial Drugs: What’s Better for COVID-2019 Treatment?

Hydroxychloroquine and chloroquine are known antimalarials which have showed clinical benefits for patients with coronavirus. Both have been reported to be well-tolerated in individuals administering it for COVID treatment. But what’s the difference between them, and what medication can treat the disease with better efficiency?

covid treatment malarial drugs

Hydroxychloroquine vs Chloroquine – Indications for Use

Both medicines are used to treat malaria and certain autoimmune diseases. However, Hydroxychloroquine (Plaquenil) is considered more effective in the fight against Plasmodium vivax, P. ovale and P. Malariae (malaria pathogens), as these protozoa have developed some resistance to chloroquine. This is possibly due to the fact that hydroxychloroquine appeared on the market later than its competitor.

In addition, hydroxychloroquine has been tested to treat Sjögren syndrome, an autoimmune disease characterized by increased dry mucous membranes, such as dry skin and vaginal dryness.

Chloroquine was the first remedy from the class of antimalarials to show impressive results in the treatment of COVID-2019 (even Trump reported that), and then it was suggested that hydroxychloroquine, its less toxic metabolite, should also have a similar effect. This hypothesis was clinically confirmed and a number of new studies are ongoing.

Hydroxychloroquine vs Chloroquine: Effectiveness for the Treatment of Coronavirus

According to a study by Chinese researchers Xueting Yao et al. published on 09 March 2020, Hydroxychloroquine was found to be stronger than chloroquine. The experiment was done in vitro, so to confirm this statement, studies with participation of people with COVID are needed. The scientists suggested the following dosage and treatment regime with hydroxychloroquine: 400 milligrams twice daily for 4 days.

However, there are other options (described by the US authorities) with higher initial dosage.

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When it comes to chloroquine, there are pretty clear instructions from Chinese healthcare professionals who have recommended taking 500 mg 2 times a day for 10 days.

Availability of Medications

Hydroxychloroquine features wide availability compared with the older medication. It has been administered by some hospitalized people suffering from COVID-2019 in several countries, including in the US.

Chloroquine was widely available in the past, but now it is supplied in pharmacies in lower quantities, because more effective antimalarial medications have entered the pharmaceutical market.

Side Effects of Hydroxychloroquine and Chloroquine

The medications can cause the following side effects: gastrointestinal disorders, dose-related retinopathy, liver disorders, weight loss, anorexia, heart problems, reduced appetite, headache, seizures, etc.

However, hydroxychloroquine is considered a safer choice when it comes to probability of adverse reactions. In particular, scientists D. Finbloom, K. Silver and others (The Journal of Rheumatology, 1985) reported that hydroxychloroquine can be used safely with minimal risk of retinal toxicity in comparison with chloroquine which is associated with higher incidence of eye-related adverse events.

Overdose – Must be Avoided in Both Cases

Both medications can cause dangerous adverse reaction if consumed in elevated dosages. Overdose cases were rarely reported, but known bad effects include severe hypotension, tachycardia, eye damage, and others. Always take the medications as directed. Elevated dosage is unlikely to enhance antiviral effect but can lead to severe complications.


Hydroxychloroquine may interact with the following medications:

  • ·  digoxin (the pharmaceutical may boost levels of digoxin in blood plasma)
  • ·  insulin and antidiabetics (hydroxychloroquine may boost hypoglycemic effects of antidiabetic injections or pills)
  • ·  meds that cause QT interval prolongation and other arrhythmogenic medications (as hydroxychloroquine also prolongs QT)
  • ·  antiepileptics (concurrent administration can enhance their antiepileptic effect)
  • ·  mefloquine (their combination may increase the risk of convulsions)
  • ·  methotrexate (their simultaneous administration is unstudied, there are assumption that it can aggravate the risk of adverse events)
  • ·  cyclosporine (co-administration boosts its plasma levels)

Chloroquine has the following interactions:

  • ·  ampicillin (its levels may be decreased due to chloroquine)
  • ·  antacids and kaolin (they can reduce absorption of the medication)
  • ·  cimetidine (can lead to amplification of chloroquine levels)
  • ·  mefloquine (increased risk of convulsion, as in the case with hydroxychloroquine)
  • ·  cyclosporine (plasma levels of this immunosuppressant may increase, similarly to hydroxychloroquine)

The Bottom Line

Both medications belong to classes of antimalarials and medications for autoimmune diseases. They feature similar mechanism of action, which has surprisingly allowed medics to use them in clinical practice to treat coronavirus disease. Hydroxychloroquine has higher availability and is dispensed more widely. This medication is less tested than chloroquine in terms of coronavirus therapy and there is a lack of use guidelines, but potentially it can work more efficiently than its rival and it is considered safer for general health.


Dr. Douglas Goldberg, MD is a Cardiology Specialist in Mineola, NY. He is affiliated with medical facilities Nyu Winthrop Hospital and Mercy Medical Center.