Favipiravir-induced cutaneous adverse reactions in patients infected with COVID-19.

Favipiravir (FVP) has been used for treatment of COVID-19 in many countries. We analysed the incidence of FVP-induced cutaneous adverse reactions (CARs) in patients infected with COVID-19 who were hospitalized at Bamrasnaradura Infectious Diseases Institute, a principal centre of emerging infectious disease in Thailand, and who presented with cutaneous eruption following FVP prescription. We identified five cases of FVP-induced CARs: two patients with maculopapular rash, two with urticarial rash, and one with Stevens-Johnson syndrome. The median interval between FVP treatment and rash occurrence was 7 days and the mean duration of the rash was 5 days. This report highlights that FVP can induce CARs, particularly eruptions, in COVID-19-infected patients. Clinicians should be aware of this possible drug-related allergy, and it should be excluded as a cause of rash during FVP treatment of COVID-19.