Background Bromhexine is a potent inhibitor of transmembrane serine protease 2 and appears to have an antiviral effect in controlling influenza and parainfluenza infection; however, its efficacy in COVID-19 is controversial.

Methods A group of hospitalized patients with confirmed COVID-19 pneumonia were randomized using 1:1 allocation to either standard treatment lopinavir/ritonavir and interferon beta-1a or bromhexine 8 mg four times a day in addition to standard therapy. The primary outcome was clinical improvement within 28 days, and the secondary outcome measures were time to hospital discharge, all-cause mortality, duration of mechanical ventilation, the temporal trend in 2019-nCoV reverse transcription-polymerase chain reaction positivity and the frequency of adverse drug events within 28 days from the start of medication.

Results A total of 111 patients were enrolled in this randomized clinical trial and data from 100 patients (48 patients in the treatment arm and 52 patients in the control arm) were…