To the editor:

Coronaviruses (CoVs) usually affect the respiratory system of mammals causing mild to severe infections. In the past two decades pathogenic human CoVs with high morbidity and mortality such as severe acute respiratory syndrome coronavirus (SARS-CoV) and Middle East respiratory syndrome coronavirus (MERS-CoV) emerged from animal reservoirs.

The current global coronavirus disease 2019 (COVID-19) pandemic, caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), lead to death over 6 million of people worldwide. It represents a challenge for all healthcare systems and for the countries that have dealt with unprecedented social and economic consequences. Since the COVID-19 pandemic began, numerous drugs have been proposed to treat or prevent COVID-19. Along with the search for new drugs, existing drugs with known pharmacokinetics/dynamics and safety profiles have been repurposed beyond traditional use. In fact, compared to de novo drug discovery, drug repurposing could be an effective research strategy to shorten time and reduce costs. A retrospective cohort study by Karimpour-Razkenari et al. on the effects of melatonin in COVID-19 ICU patients has been recently published in this journal. Authors showed only marginal effect on disease-specific biochemical parameters and a non-statistically significant reduction in mortality in melatonin-receiving group (41%) vs non melatonin-receiving group (72%).