Fig. 1

In vitro testing of diacerein pharmacokinetics. a Treatment regime of 1% diacerein ointment onto porcine skin model and sampling of Franz diffusion cell receptor medium and skin biopsy at final time point followed by mass-spectometry analysis of rhein levels. b Mass-spectrometric quantification of receptor medium samples showed accumulation of rhein over time. c After 72 h rhein was detected in both, receptor medium and skin biopsy, but no diacerein was detected at any time point. On average, approximately 40% of transformed rhein was retained within the skin (n = 5)