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The degradation of phenylbutazone was studied in the presence of lakes suitable for coloring the sugar coats of phenylbutazone tablets. The drug was degraded, in light, in the presence of erythrosine sodium. The degradation probably proceeds via singlet oxygen generated by the light-exicited dye. The degradation may be important in some quality control procedures and can lead, for example, to unusual results in dissolution rate testing.

Bilirubin dynamics were studied in homozygous Gunn rats under normal room lighting conditions and under conditions simulating phototherapy. A kinetic model was developed for the formation, distribution, and elimination of bilirubin. The decrease in plasma bilirubin concentration during illumination with low intensity [300 footcandles (fc)] and high intensity (1000-1100 fc) light was studied. The plasma bilirubin concentration in the rats decreased under phototherapy until a new steady-state concentration was reached, the decline being more rapid under high intensity light conditions. Gunn rats were also injected with a tracer dose of 14C-bilirubin following a period during which the rats were illuminated with low or high intensity light. The distribution and elimination of the labeled bilirubin were followed under continuous illumination. The chosen kinetic model, when adapted to the set of data under investigation, fit all of the data concerning bilirubin kinetics in Gunn rats under continuous illumination.