Isn't the dose of 1600 mg of Xifaxan per day too high?

Indeed, the most commonly used doses of rifaximin do not exceed 1200 mg/day in adults. However, there are reports that increasing the daily dose to 1600 mg was associated with higher efficacy without aggravating adverse reactions. I enclose a link to the source I used: https://pubmed.ncbi.nlm.nih.gov/17373916/ The doctor may use different doses than those presented in the package leaflet. It does this on the basis of the latest medical knowledge, which, unfortunately, in many cases is difficult to find in leaflets. We refer to this use of the drug as "off-label", and you can read more about it here: https://www.gdziepolek.pl/artykuly/leczenie-off-label-poza-wskazaniami