bromhexine for post-exposure covid-19 prophylaxis: a randomized, double-blind, placebo-controlled trial

Background: limited medications are available for post-exposure prophylaxis of coronavirus disease 2019 (covid-19) infection. whether bromhexine can prevent or mitigate symptomatic infection after virus exposure is undetermined. objectives: we aimed to evaluate bromhexine's effect on preventing covid-19 after close contact exposure. methods: a multi-center randomized, double-blind, placebo-controlled clinical trial was conducted on 372 adults (≥ 18 years) who had close contact within four days with a household member with confirmed covid-19. they were randomly assigned to receive bromhexine 8 mg (n = 187) or placebo (n = 185) three times a day for two weeks. the primary outcome was the incidence of symptomatic covid-19. secondary outcomes included hospitalization or death, confirmed covid-19 by polymerase chain reaction (pcr) in symptomatic patients, and adverse drug reactions. results: the incidence of symptomatic covid-19 was significantly lower in individuals who received bromhexine than in those who received the placebo (16 [8.6%] vs. 34 [18.4%], relative risk = 0.47, p = 0.005). pcr confirmation was reported in 13 (7.0%) and 26 (14.1%) individuals in the bromhexine and placebo groups, respectively (p = 0.025), with a relative risk reduction of 50%. the hospitalization rate, death, and medication side effects did not vary significantly between the bromhexine and placebo arms. conclusions: bromhexine is an effective, non-invasive, affordable agent with a low side-effect profile to prevent symptomatic covid-19. early use of bromhexine potentially provides another layer of protection; hence, it can play a role in controlling the pandemic.