Abstract: Original Article The effects of colchicine on hospitalized COVID-19 patients: A randomized, double-blind, placebo-controlled clinical trial Journal of Investigative Medicine 2023, Vol. 00(0) 1–8 Ó 2023 American Federation for Medical Research Article reuse guidelines: sagepub.com/journals-permissions DOI: 10.1177/10815589221141815 journals.sagepub.com/home/imj Hossein Kasiri1, Mobin Ghazaiean2, Nima Rouhani3, Fahimeh Naderi-behdani1, Monireh Ghazaeian4, and Robabeh Ghodssi-Ghassemabadi5 Abstract This study was designed to evaluate the effects of colchicine in the improvement of clinical outcomes of hospitalized COVID-19 patients. This prospective, randomized, double-blind, placebo-controlled clinical trial was conducted on adult patients (.18 years) with severe COVID-19. The included patients were randomly (1:1) assigned to the colchicine (2 mg loading dose followed by 0.5 mg twice daily for 7 days) or placebo group. Both groups received remdesivir and interferon beta-1b. The primary outcome of the study was to receive clinical response as ordinal scale of 1 or 2. Secondary outcomes were hospital complications and 28-day mortality. Between February and May 2021, 110 patients were included and 106 of them were analyzed. Baseline clinical characteristics and demographics were not significantly different. According to the ordinal scale, 30 patients in the control group (58.8%) responded to treatment within 7 days, while 35 patients (63.6%) in the colchicine group showed the same response (p = 0.61, odds ratio (OR) = 1.23, 95% CI [0.560–2.68]). On the 14th day, 87.3% of the colchicine group (n = 48) and 82.4% of the control group (n = 42) responded (p = 0.48, OR = 1.47, 95% CI [0.50.3–4.29]. In addition, 28-day mortality, intensive care unit admission, and hospital duration were not different between the groups (p = 0.99, 0.59, 0.06). Diarrhea and nausea were the major side effects dominant in the colchicine group. Colchicine showed no beneficial effects on clinical improvement and hospital complications in patients with COVID-19. Moreover, in case of prescription, the safety concerns of colchicine, specially gastrointestinal side effects, should be taken into account. Keywords Colchicine, COVID-19, efficacy