There have been early indications that these drugs may be effective in treating or preventing Covid-19, but the medications haven’t endured the due diligence of extensive clinical trials and there have been growing concerns about the impact chloroquine and the closely related hydroxychloroquine can have specifically on the heart.
“In a better world, if we weren’t so panicked about this virus, we would wait and see if this drug had some value other than the President declaring that it has some value,” Offit said. “If someone’s sick you can still hurt them.”
He added, “but there is this residual concern.”
World Health Organization officials on Monday said they “eagerly await” the outcomes of studies evaluating the use of chloroquine and hydroxychloroquine as possible Covid-19 treatment options, especially as the drugs already are being used “off label” to treat some patients in certain countries.
Currently, “there is no evidence from randomized control trials that it works and clinicians have also been cautioned to look out for side effects of the drug to ensure that first we do no harm,” Ryan said. “We eagerly await the outcome of the trials that are underway.”
Small chloroquine study ends early in Brazil due to deaths
A preliminary study out of Brazil on the use of chloroquine diphosophate to treat patients with Covid-19 symptoms ended early after several patients died and researchers found that a high dose of the drug was associated with a severe type of arrhythmia, or irregular heartbeat.
The pre-print study included 81 patients who were hospitalized with severe respiratory syndrome in Manaus, Brazilian Amazon. Patients were enrolled in the study before receiving laboratory confirmation of Covid-19, but Lacerda said that 75% of the patients ended up confirmed and the others were “very likely” but their tests came out negative.
For the trial, patients either received a high dose of chloroquine, at 600mg twice daily for 10 days for a total dose of 12g, or they received a low dose at 450mg for five days, twice daily only on the first day, for a total dose of 2.7g. All patients also received the antibiotics ceftriaxone and azithromycin as part of their treatment. A limitation of the study is that there were no patients receiving a placebo.
By the sixth day of the trial, the researchers halted the study after 11 patients died — and even more deaths were counted in the study’s updated data.
In the new updated version of the study that was submitted for publication, “we have 16 deaths out of 41 in the high dosage, and 6 out of 40 in the low dosage. This is significantly different,” Lacerda said in the email.
“Patients were also using azithromycin and oseltamivir, which are also cardiotoxic drugs,” he said. “Low dose seems to be safer in these patients, however because we have no local controls (not using the drug), because it is being routinely used in Brazil, more efficacy studies need to be performed.”
The Data Safety and Monitoring Board for the study “recommended the immediate interruption of the high dose arm and that all patients in it were unmasked and reverted to the low dose arm,” the researchers wrote in the pre-print study.
The higher dose showed “no apparent benefit” against Covid-19, although the researchers noted their study size was small.
“The major difference between the high dose and the low dose group occurred during the first three days and the actual toxicity — two patients in the high dose chloroquine arm developed ventricular tachycardia before death,” said Vanderbilt University’s Schaffner, who was not involved in the study.
“So it’s clear that the high dose group was more toxic but it’s not as though the low dose group was without concern and in larger studies you might find some problems with the low dose group as well,” he said.
“In conclusion, the high CQ dose scheme (12g), given for 10 days, was not sufficiently safe to warrant continuation of that particular study arm,” the researchers wrote in the study, adding that they strongly recommend that this dosage is no longer used for the treatment of severe Covid-19.
Swedish hospitals directed not to use chloroquine for Covid-19
Hospitals in Sweden have received guidance directing clinicians not to use chloroquine to treat Covid-19 patients outside of clinical trials.
Magnus Gisslén, professor and senior doctor at the Sahlgrenska University Hospital in Gothenburg, Sweden, told CNN last week that the guidance also applies to the related medication, hydroxychloroquine.
The guidance states that “considering the very low evidence of any significant effect on Covid-19 and since serious side effects can’t be ruled out, the use of chloroquine outside of clinical trials is not recommended.”
“We stopped using it a few weeks ago after only a very limited use,” Gisslén said. “We have recommended it to all hospitals in our region to stop using it. I think almost all hospitals in the country have now stopped using it.
“This medicine has no effect that we have been able to see on the treatment of Covid-19.”
Gisslén and his colleagues have seen “a serious effect on the heart” linked to using the medication, he said. He added that patients with lower kidney function also had a difficult time taking the drug.
The patients most at risk are those with pre-existing conditions in the heart, Gisslén said. “Those are often the older patients,” he said. “But if you get a too high dosage it can affect people who have no underlying conditions at all.”
In the United States, the drugs have been commonly used in combination with the antibiotic azithromycin. Gisslén said the drugs have not been used with antibiotics in Sweden.
Ulla Wändel Liminga, scientific director of pharmacovigilance at the Swedish Medical Products Agency, said that while the agency hasn’t issued specific guidance on the drugs, “the use of chloroquine and hydrochloroquine should only be used within clinical trials on Covid-19 patients.”
Liminga last week counted about five incident reports of serious side effects in Covid-19 patients in Sweden.
“These side effects are mostly well known and are mainly concerning the heart. In the worst case, the side effect could be cardiac arrest and eventually death,” she said.
The agency is not aware of any deaths due to cardiac arrest resulting from chloroquine, however, it has seen one death with an unclear relationship to the drug.
“I don’t know how much this medicine has been used in Sweden,” said Liming. “But there is no evidence that it has any positive effects when used as a preventative drug. This is why we are saying that it should only be used in clinical trials on Covid-19 patients.”
Heart doctor groups weigh in
Harrington said, “While these medications may work against COVID-19 individually or in combination, we recommend caution with these medications for patients with existing cardiovascular disease.”
CNN’s Minali Nigram contributed to this report.