Coronavirus Episode 14: Is Chloroquine a Cure?

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chloroquine coronavirus 2

I skipped episode 13 because, well this pandemic is bad enough without having an episode 13. On another note, there’s been a huge amount of buzz lately about using chloroquine, a malaria drug, to treat COVID-19. So what data do we have? Is this a real thing or more hype at this point? Let’s dig in.

What is Chloroquine?

In certain parts of the world, the mosquito-borne illness known as malaria is rampant. One of the most common and inexpensive treatments is a drug discovered in 1934 called chloroquine or hydroxychloroquine (1). It’s a quinine analog, which itself is a drug that comes from the bark of the cinchona tree which is native to central and South America, the Caribbean and western Africa. Quinine is what gives tonic water it’s bitter taste. Tonic water contains under 100mg of quinine per liter, which is much lower than the 500mg to 1,000mg in quinine tablets.

Chloroquine and COVID-19

Here’s what we know:


In-vitro means a lab experiment, usually in cells. In one study, researchers took human cells and infected them with COVID-19 and then looked at the ability of the virus to make more of itself (2). It blocked both the entry of the virus and also hit the virus after entering the cells. Others have also found the same thing (3). Hydroxychloroquine, which is a less toxic form of chloroquine, has also been shown to inhibit the virus in lab experiments (7).

In Animals

The same effects have been observed in mice who were infected with the coronavirus (4). Those that were placed on higher doses survived, while low or no dose chloroquine resulted in the death of the mice:

coronavirus chloroquine

In Humans

The Chinese Health Ministry put out this statement, “results from more than 100 patients have demonstrated that chloroquine phosphate is superior to the control treatment in inhibiting the exacerbation of pneumonia, improving lung imaging findings, promoting a virus-negative conversion, and shortening the disease course according to the news
briefing”. However, no data was shown to back up that statement.

The Journal of Critical Care published a review of six different articles and 23 ongoing clinical trials in China. Their conclusion was that while the lab and animal data was compelling, there is no good clinical data yet that shows that this treatment is effective for the coronavirus (6). Hence, we really don’t know if this drug will work in patients with COVID-19 or at least the Chinese have yet to share their data.


Chloroquine has some side effects like nausea, diarrhea, and loss of appetite. There has been a discussion of the drug’s cardiac effects, including possibly causing heart rhythm problems. However, deeper research shows that this is less of an issue (8,9). In addition, WHO published guidelines in 2017 showing that whatever heart toxic effects were present were rare (10).


A couple in Arizona yesterday mistakenly thought that a popular fish tank additive that has chloroquine was safe to ingest (11). It was not and this stuff ended up killing him with his wife in the ICU. Hence, please be careful out there!

The upshot? Chloroquine has promise as a COVID-19 treatment. However, it’s not yet proven until we see the Chinese data. Even then, there will be more testing. However, I’m sure we’ll see more compassionate use by doctors on the front lines and possibly more to come from FDA on this issue.



(1) Parhizgar AR, Tahghighi A. Introducing New Antimalarial Analogues of Chloroquine and Amodiaquine: A Narrative Review. Iran J Med Sci. 2017;42(2):115–128.

(2) Wang M, Cao R, Zhang L, et al. Remdesivir and chloroquine effectively inhibit the recently emerged novel coronavirus (2019-nCoV) in vitro. Cell Res. 2020;30(3):269–271. doi:10.1038/s41422-020-0282-0

(3) Wang, M., Cao, R., Zhang, L. et al. Remdesivir and chloroquine effectively inhibit the recently emerged novel coronavirus (2019-nCoV) in vitro. Cell Res 30, 269–271 (2020).

(4) Keyaerts E, Li S, Vijgen L, et al. Antiviral activity of chloroquine against human coronavirus OC43 infection in newborn mice. Antimicrob Agents Chemother. 2009;53(8):3416–3421. doi: 10.1128/AAC.01509-08

(5) Gao J, Tian Z, Yang X. Breakthrough: Chloroquine phosphate has shown apparent efficacy in treatment of COVID-19 associated pneumonia in clinical studies. Biosci Trends. 2020 Mar 16;14(1):72-73. doi: 10.5582/bst.2020.01047.

(6) Cortegiani A, Ingoglia G, Ippolito M, Giarratano A, Einav S. A systematic review on the efficacy and safety of chloroquine for the treatment of COVID-19. J Crit Care. 2020 Mar 10. pii: S0883-9441(20)30390-7. d

(7) Liu, J., Cao, R., Xu, M. et al. Hydroxychloroquine, a less toxic derivative of chloroquine, is effective in inhibiting SARS-CoV-2 infection in vitro. Cell Discov 6, 16 (2020).

(8) Wozniacka A, Cygankiewicz I, Chudzik M, Sysa-Jedrzejowska A, Wranicz JK. The cardiac safety of chloroquine phosphate treatment in patients with systemic lupus erythematosus: the influence on arrhythmia, heart rate variability and repolarization parameters. Lupus. 2006;15(8):521-5.

(9) Teixeira RA, et al. Evidence for cardiac safety and antiarrhythmic potential of chloroquine in systemic lupus erythematosus, EP Europace, Volume 16, Issue 6, June 2014, Pages 887–892,

(10) World Health Organization. The cardiotoxicity of antimalarials. Malaria Policy Advisory Committee Meeting. 22–24 March 2017, Geneva, Switzerland.

(11) New York Times. Man Fatally Poisons Himself While Self-Medicating for Coronavirus, Doctor Says. Accessed 3/24/20.

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10 thoughts on “Coronavirus Episode 14: Is Chloroquine a Cure?

  1. Sam

    The recommended dosage is 500 mg of chloroquine twice a day in patients with mild, moderate and severe forms of COVID-19 pneumonia.

  2. Bri

    Curious about the trials performed in mice. I was under the impression that SARs-CoV2 was not able to infect other animals besides humans, so I imagine the strain being used in those trials is slightly different. How should this data be interpreted if that is the case?

    1. Chris Centeno, MD Post author

      The study at the link in the citation.

  3. Edith(Edy)Johnson

    Glad for update.


    If quinolone drugs can potentially cause tendon rupture and nerve damage, could chloroquine cause any similar damage? Thank you

    1. Chris Centeno, MD Post author

      These are not in the same drug category.

  5. Douglas Kunce

    New insights on the antiviral effects of Chloroquine.

    Chloroquine is an amine acidotropic form of Quinine.

  6. Reiner Kremer

    Thank you for this post. Is there a difference in efficacy between hydroxychloroquine and chloroquine?

    1. Chris Centeno, MD Post author

      Hydroxy has fewer side effects and looks like the better choice.

  7. Sam

    Another treatment protocol for COVID-19 patients, in the absence of contraindications, is: Hydroxychloroquine (200mg, 3 times per day, for 10 days) with or without Azithromycin (500mg on day1 followed by 250mg/day the next 4 days to prevent bacterial super-infection – these patients were also put under daily ECG control) depending on clinical presentation. At day6 post-inclusion, 100% of patients treated with Hydroxychloroquine and Azithromycin combination were virologicaly cured comparing with 57.1% in patients treated with hydroxychloroquine only, and 12.5% in the control group.
    The result/statistics of this preliminary non-randomized clinical trial (20 March 2020) was presented with some exclusions/omissions/limitations. Read the entire study for the full picture.

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