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Over 300 international researchers from the Observational Health Data Sciences and Informatics (OHDSI) community studied data from almost 1 million patients. They declared hydroxychloroquine safe for short-term use, but urge caution in using it in combination with azithromycin.

Hydroxychloroquine spelt out in blocks
The largest analysis to date on the safety of the drug hydroxychloroquine, found there were no worrying side effects

In the face of the rapid spread and escalation of the coronavirus, many decisions are being made quickly and a number of therapies are being trialled for its treatment. One of these is the use of hydroxychloroquine, a drug approved in 1950's for the treatment of malaria, lupus and rheumatoid arthritis.

In the last few days in the USA the FDA has approved the use of hydroxychloroquine for compassionate use in the treatment of COVID-19. Despite the lack of evidence of its clinical effectiveness, President Donald Trump says the drug has shown 'very encouraging results' in treating coronavirus.

Led by Prof Dani Prieto-Alhambra, Professor of Pharmaco- and Device Epidemiology at the Centre for Statistics in Medicine (NDORMS), a team of researchers from around the world set out to analyse the safety profile of hydroxychloroquine.

In what is the largest analysis to date on the safety of the drug, the team used data from fourteen datasets to analyse the medical history of over 950,000 patients who have previously taken hydroxychloroquine. Patient data came from six countries: Germany, Japan, the Netherlands, Spain, the UK, and the USA. 

"Our aim was to look at what side effects people who have taken hydroxychloroquine have had in the past, as given its mechanism of effect it could potentially cause adverse outcomes including arrhythmia, cardiovascular disease, venous thromboembolism, liver or kidney failure," said Dani. "As it's now being widely used globally to treat the coronavirus, we were concerned to know that the use of the drug would not cause a second set of complicated side effects for patients."

The team did not find any consistent signals that made them think that the drug is not safe in the short term. "When administered at the doses used for current indications like rheumatoid arthritis, we have not detected any worrying side effects. We therefore think that it's quite a safe medication in general for short-term use," said Dani. "However, when prescribed in combination with azithromycin, it may induce heart failure and cardiovascular mortality and we would urge caution in using the two together.” A pre-print (not yet peer reviewed) of these findings is now available from MedRXiv.

"We lack data on the safety of hydroxychloroquine when used at higher doses, and it is too early to be able to understand its clinical effectiveness to treat COVID-19. Randomised controlled trials are underway that will define the anti-viral efficacy of this treatment, including research at Oxford using hydroxychloroquine on 3,000 high-risk patients to see if it can alleviate the worst of the symptoms. We'll conduct a new study amongst COVID-19 patients when data starts accumulating."

The research was part of a four-day virtual study-a-thon that brought over 300 researchers from the OHDSI international community together to provide real-world evidence and inform healthcare decision-making in response to the current global pandemic.

Taking place from 26 – 29 March the teams from 30 countries and six continents explored multiple study areas including the safety of proposed drugs and the effects of various treatments on historical viral diseases, as well as predicting outcomes for patients with viral symptoms or complications. Results are being collated and are expected soon.