Get my point!!
I haven't said you can not use a systemic drug to treat the gastrointestinal tract. Nystatin and oral Amphotericin B aren't absorbed for the blood and they act in the gut. Thse drugs were made to treat the gastrointestinal tract from mouth to anus, and of curse topical too. Amphotericin B works as a systemic drug when is used in IV form. Again, since Nystatin was created, there isn't any other drug I am aware of to treat specificly the gut. There are one of two more which are used in Europe, and not available in US. I mean, created thinking in to cure an intestinal candidiasis.