My 52 Yr Old Fiancé Has Been Told His Liver

my 52 yr old fiancé has been told his liver is shutting down. his blood is thin and he is high risk for surgery. he was prescribed xifaxan, took for five days and then his insurance has refused to authorize it. will he have any adverse effect from not continuing or is there a comparable drug available? can't speak to insurance over the weekend....so frustrating.