The molecular groups of umifenovir - hydroxy, amino and carboxy - can form different hydrogen-bonded synthons.

Crystalline solvates and other solid forms may be determined by the spatial structure and conformational equilibria in the saturated solution.

[24][25] In 2006 the American company Good Earth Medicine applied to the FDA for an Emergency Use Authorization of Arbidol during the H5N1 bird flu epidemic, but their application was rejected on the grounds that the lab data provided was not strong enough to justify use.

[26][27] In 2007, the Russian Academy of Medical Sciences stated that the effects of Arbidol (umifenovir) are not scientifically proven.

[28] In the early 2010s Russian media criticized lobbying attempts by Tatyana Golikova (then-Minister of Healthcare) to promote umifenovir,[29] and the unsubstantiated claim that Arbidol can speed up recovery from flu or cold by 1.3-2.3 days.

Shortly afterwards the Russian Federal Antimonopoly Service fined the company for violation of its advertising rules.

[35][36][37][38][39] A three-arm RCT study published in May 2020 in the Cell Press journal Clinical Advances found that neither Umifenovir or Lopinavir/Ritonavir helped patients with mild to moderate COVID-19.

[41] A systemic review and meta-analysis of 16 studies on Umifenovir published in March 2021 concluded that there is "no significant benefit of using Arbidol compared with non‐antiviral treatment or other therapeutic agents against COVID‐19 disease.