A new study concluded that taking chloroquine does not prevent covid-19, the disease caused by the new coronavirus.
Scientists at the University of Pennsylvania in the United States tested whether the drug, used against lupus and malaria, had this effect on 125 health professionals.
Participants were divided into two groups: 64 received chloroquine and 61 received placebo for eight weeks.
In the end, it was found that there was no significant difference in the proportion of people who were infected.
There were four cases in each group, which represented 6.3% of volunteers who took chloroquine and 6.6% of those who took placebo.
“With that, we cannot recommend the routine use of hydroxychloroquine among health professionals to prevent covid-19”, say the authors of the research, which was published this Thursday (9/30) in Jama Internal Medicine, scientific journal of American Medical Association.
The results of the study are not surprising, says infectologist Raquel Stucchi, a professor at the State University of Campinas (Unicamp), because they reinforce other scientific evidence obtained so far that hydroxychloroquine is not effective against the coronavirus.
“I already had a lot of hope that chloroquine could work, but this has not been proven over the months, and this study reaffirms what we already knew. But it is important to have this documented scientifically, because one thing is that a doctor does not prescribe this medicine because he doesn’t like it or has the impression that it won’t work and another is not to do it because science has shown that it doesn’t work “, says Stucchi.
The study authors also pointed out that participants who had covid-19 had no symptoms or had only mild signs of the disease. Everyone has fully recovered.
Volunteers who took chloroquine had more side effects than those who used placebo, especially diarrhea (32% in the first group compared to 12% in the second). But there were no serious reactions.
The study was terminated before recruiting all 200 participants initially expected, because a review of the results obtained after the survey passed 100 volunteers has already pointed out the ineffectiveness of hydroxychloroquine to prevent covid-19.
According to mathematical models, even if the research continued to the end, this result would not be changed. In such cases, it could be considered unethical to proceed with the research, which was then completed.
Previous study came to the same conclusion
A study published in June in the scientific journal The New England Journal of Medicine had reached the same result.
The survey was attended by 821 volunteers from the United States and Canada who had come into contact with people infected with the new coronavirus.
Participants took the drug or placebo for five days after exposure to the virus. According to the study authors, there was no significant difference between the proportion of infected people in the two groups.
The authors of the new study refer to this research and claim that one of the criticisms made of that investigation is that the volunteers started taking the drug three to four days after contacting someone who had the virus.
This “has raised criticism that the delay in starting hydroxychloroquine may have missed a key biological window to prevent transmission,” say researchers at the University of Pennsylvania.
Therefore, they decided to test the use of the drug before exposure, but also concluded that it was not effective.
However, they make a reservation: “Given the small sample size, we cannot rule out a small undetected potential prophylactic effect”.
Scientists also claim that the participants were healthy and relatively young (with an average age of 33) and that, therefore, the results obtained could not be generalized to the entire population, especially among people of older age or who have other diseases, which in both cases are risk factors for covid-19.
“We also cannot rule out the possibility that a smaller or intermittent dose of hydroxychloroquine is more efficient for prevention, although preclinical investigations with monkeys have not found differences in antiviral activity at different dosages,” say the authors.
“Ongoing prophylaxis tests will be important to address these limitations.”
Trump and Bolsonaro
The possible effect of chloroquine to prevent covid-19 was considered by authorities and health professionals, although there was no concrete scientific evidence for this.
In May, US President Donald Trump said he was taking the drug to prevent the disease.
Asked why he was doing this even without scientific evidence of this effect, Trump said, “Because I think it’s good. I heard a lot of stories.”
Also in May, the Brazilian government announced, through the Itamaraty, that the 2 million doses of hydroxychloroquine donated by the United States would be used as “prophylactic”, a medical term used for disease prevention measures, to “help defend nurses, doctors and health professionals in Brazil against the virus “.
The drug was even distributed for the same purpose by the city hall of some cities, such as Campo Grande, in Mato Grosso do Sul, and Gravataí, in Rio Grande do Sul.
In Brusque, Santa Catarina, the health plan Unimed even gave a kit with hydroxychloroquine, ivermectin, vitamin D and zinc that supposedly would prevent health professionals who are on the front line of the pandemic from becoming ill.
President Jair Bolsonaro (without a party) is an advocate of hydroxychloroquine, but he usually encourages its use not for prevention, but in the early stages of the disease. Bolsonaro said he used the drug when he had the disease in July.
The Ministry of Health authorizes hydroxychloroquine to be prescribed for both mild and severe cases.
The great demand for the drug at the beginning of the year led the National Health Surveillance Agency (Anvisa) to place the chloroquine under a special sale control regime, which requires a special prescription and the prescription retention in the pharmacy.
“Among health professionals, most of us, with the exception of a few, have already bowed to scientific evidence, even those who were favorable,” says Stucchi.
“Everyone wants to have a medicine, without a doubt, we are eager for a medication that can abort the evolution of the disease, prevent a serious form or serve as prophylaxis. Perhaps the belief in this is supported by political stubbornness, but, scientific, this is no longer sustainable. “
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