Testing of umifenovir's efficacy has mainly occurred in China and Russia,[5][6] and it is well known in these two countries.[7] Some of the Russian tests showed the drug to be effective[5] and a direct comparison with Tamiflu showed similar efficiency in vitro and in a clinical setting.[8] In 2007, Arbidol (umifenovir) had the highest sales in Russia among all over-the-counter drugs.