Bioassay for determination of nystatin in faeces after oral application.

An optimized bioassay (agar diffusion assay) using a defined Candida albicans strain as tester strain for determination of nystatin excreted with the faeces during and after oral application is presented. The sensitivity of the test achieves 39 IU nystatin/g faeces relating to the total amount of nystatin (using dimethylformide for solution of nystatin in the faeces) and 78 IU nystatin/g faeces relating to the biologically active portion (using aqua dest for suspension of nystatin from the faeces). Precision and reproducibility of the bioassay are assured by standardized procedures. By means of the bioassay, doses and application intervals for orally administered nystatin can be optimized.