Concentrations of nystatin in faeces after oral administration of various doses of nystatin.

Nystatin was administered in ten healthy adult volunteers in increasing doses of 3 X 10(6) I U, 6 X 10(6) I U, 9 X 10(6) I U and 12 X 10(6) I U per day, each dose being given for a five-day period. Faecal samples were collected daily for the determination of their concentration of biologically active nystatin. Nystatin concentrations were determined biologically; the sensitivity of this method was less than or equal to 20 mcg/g of faeces. During the four treatment periods with increasing doses, 38%, 31%, 26% and 20% respectively of the faecal samples contained biologically undetectable amounts of nystatin. This means that nystatin is either inactivated or unevenly distributed through the intestinal contents, or both. The practical consequences of this may be that in a significant portion of the colon there is no inhibitory nystatin concentration against Candida albicans, despite treatment with as much as 12 X 10(6) I U of nystatin per day.