Thank you for your query at DoctorSpring.com.
I understand your concern and will do my best to help you.
Xifaxan (Rifaximin) is an antibiotic which is locally acting, meaning that when its taken orally, it has its effect on the gut. It is not absorbed from the gut into the bloodstream like the majority of other antibiotics and drugs. Hence it is used for infections of the gut like Small Intestinal Bacterial Overgrowth (SIBO).
Alcohol can decrease efficacy of certain antibiotics which have systemic effects, that is those which act through the bloodstream. This it does by increasing the enzymes in the liver which breakdown the antibiotics, thus decreasing their levels in the bloodstream and weakening their effect. Since Xifaxan does not even enter the bloodstream, alcohol does not have any affect on it. So you need not worry about the heavy drinking affecting its efficacy.
However, binge drinking is generally unhealthy and is best avoided.
I hope this was helpful. Feel free to ask queries.