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Covid-19 and hydroxychloroquine (Plaquenil°): new data show no evidence of efficacy

NEWS UPDATE The results of a new randomised comparative but non-blinded trial of high-dose hydroxychloroquine (Plaquenil°) versus standard care in 150 patients hospitalised for covid-19 have been published. The only notable difference between the groups was the high incidence of adverse effects in the group treated with hydroxychloroquine. The results of other studies (non-randomised and providing only low-quality evidence) show no evidence that hydroxychloroquine has efficacy against covid-19.

The hypothesis that hydroxychloroquine might be an effective treatment for covid-19 emerged because of the drug’s antiviral effect in vitro against the coronavirus Sars-CoV-2 (details > HERE). The results of two comparative trials of hydroxychloroquine, released in late March 2020, were inconclusive (details > HERE and > HERE). Other randomised comparative trials are underway. The results of another randomised comparative trial were released on 14 April 2020.

This trial compared hydroxychloroquine versus standard care in 150 patients hospitalised in Shanghai for covid-19 (details > here). The treatment was randomly assigned, but the trial was not blinded. The patients were aged 46 years on average, and 55% were men. Only 1% of the patients were considered to have severe disease. A particularly high dose of hydroxychloroquine was used: 1200 mg per day for 3 days, and 800 mg per day thereafter for up to 2 to 3 weeks. Half of the patients were followed up for at least 20 days or so (maximum 33 days). The only patient whose condition worsened was in the hydroxychloroquine group. Hydroxychloroquine was not shown to have an antiviral effect in these patients. A higher, and statistically significant, proportion of patients in the hydroxychloroquine group reported adverse events: 30%, versus 9% of patients in the control group.

Other non-randomised studies have compared series of patients with covid-19 according to whether or not they were treated with hydroxychloroquine shortly after admission to hospital. The results constitute only weak evidence because treatment was not randomly assigned, and the patients’ clinical condition could have influenced the choice of treatment. None of these studies showed any evidence that hydroxychloroquine has efficacy against covid-19. One of these studies, conducted in four hospitals in and around Paris, compared the outcomes of 181 covid-19 patients who required oxygen therapy for pneumonia: 84 had started receiving hydroxychloroquine (600 mg per day) within 48 hours of hospitalisation, and 97 had not received this treatment during this period (control group) (details > here). Half of the patients were at least 60 years old, and 71% were men. At the time of hospitalisation, the patients had similar respiratory rates and oxygen saturation. A history of chronic respiratory disease or cardiovascular disease was more common in the control group. Chest CT scans showing more than 50% of the lung to be affected were more frequent in the hydroxychloroquine group. There was no statistically significant difference in mortality (about 4% of patients) between the groups, or in the frequency of the composite endpoint "transfer to intensive care unit and/or death (from any cause)" (20% of patients). Patients routinely underwent electrocardiography on admission, then 3 to 5 days later. Prolongation of the QT interval to a degree that warranted discontinuation of hydroxychloroquine occurred in 9.5% of patients.

Other data, mainly focusing on the dangers of treatment with the combination of hydroxychloroquine and azithromycin, have also been released (details > HERE).

As of 15 April 2020, there is still no treatment known to reduce the risk of progression to severe covid-19. Exposing patients to hydroxychloroquine and azithromycin increases the risk of serious cardiac adverse effects.

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