<<Disclaimer: Verify this information before applying it to your situation.>> I'd like to clear up a misconception that was put forth in an earlier post. Any antibiotic whether given IV or by mouth can cause yeast overgrowth and a subsequent yeast infection. Antibiotics kill bacteria and the bacteria in the GI tract will be affected by IV administration as well as the "by mouth" route. Vancomycin is given IV for systemic infections because it is not absorbed orally. It is used orally only for times when this antibiotic is needed to kill organisms in the GI tract, like clostridium difficile when absorption isn't an issue. I would hate for someone to go to the expense to use IV antibiotics thinking they were going to avoid a yeast infection cause it just ain't so. Cindy in Texas