If i am taking xifaxan (rifaximin) for small intestinal bacterial overgrowth, is it okay to drink alcohol with it? or will it adversely affect the antibiotic

Nope: It is generally very unwise to consume alcohol while on any antibiotic - but since your intestine is trying to recover from infection I wouldn't take the chance of causing any more irritation until fully healed. Stick to water - freshen it up with slices of cucumber as this has antioxidant properties and may help with some of the irritation. http://www.webmd.com/drugs/2/drug-91340/xifaxan-oral/details#interactions