New York: Researchers in the US have urged a temporary prohibition on prescribing chloroquine or hydroxychloroquine (HCQ), with or without azithromycin, to treat or prevent Covid-19.
Despite the fact that there are no therapeutic or preventive measures for the Covid-19 pandemic in the US, prescriptions of these drugs are nine times greater than in the last several years.
According to the study, published in The American Journal of Medicine, this widespread use is leading to nationwide shortages in patients with lupus and rheumatoid arthritis, for whom HCQ has been an approved indication for decades.
These patients are unable to refill their prescriptions.
“If these drugs need to be prescribed for patients with Covid-19, baseline evaluations and serial monitoring are an absolute necessity,” said study author Richard D. Shih from the Florida Atlantic University.
On March 28, the US Food and Drug Administration (FDA) issued an emergency use authorisation for chloroquine and hydroxychloroquine for the treatment of Covid-19. By April 24, however, the FDA issued a drug safety communication warning regarding hydroxychloroquine and heart rhythm disturbances that can lead to sudden cardiac death. The study authors point out that the reassuring safety profile of HCQ may be more apparent than real.
The data on safety derives from decades of prescriptions by health care providers, primarily for their patients with lupus and rheumatoid arthritis, both of which are of greater prevalence in younger and middle-age women, whose risks of fatal heart outcomes due to HCQ are reassuringly very low.
In contrast, the risks of HCQ for patients with Covid-19 are significantly higher because fatal cardiovascular complications due to these drugs are so much higher in older patients and those with existing heart disease or its risk factors, both of whom are predominantly men.
In basic research, HCQ and chloroquine are structurally related and have similar mechanisms to inhibit the virus that causes Covid-19. The authors noted that the currently available evidence is restricted to eight published studies, five on HCQ alone; two on HCQ plus azithromycin; and one on both in combination or alone.
Of these only three are randomised trials that enrolled 225, 62, and 30 patients – all too small to provide reliable evidence. All three tested hydroxychloroquine alone versus standard of care in China. One showed no significant difference in viral clearance at 28 days, the second, no difference in viral clearance at seven days, and the third, some improvements in fever, cough and chest computed tomography findings.
“With respect to hypothesis testing, only large-scale randomised trials of sufficient size, dose and duration can reliably detect the most plausible small-to-moderate effects, which can have enormous clinical and public health impacts,” said study senior Charles H Hennekens.
