Relevance of rhein excretion into breast milk

The excretion of rhein, a laxatively active metabolite of sennosides, was investigated in 100 breast milk samples of 20 post-partum women after intake of a standardized senna laxative (Agiolax), which also contains seeds of Plantago ovata as bulk substances. After daily doses of 5 g of the senna laxative containing 15 mg sennosides for 3 days, the rhein concentration in milk samples from every lactation during 24 h post-dose varied between 0 and 27 ng/ml with values below 10 ng/ml in 94%. Based on median values, 0.007% of the sennoside intake (calculated as rhein) was excreted in breast milk. None of the breast-fed infants had an abnormal stool consistency. Assuming a (theoretical) complete metabolism of sennosides to rhein in the mother, the amount of rhein delivered to the infant (ng/kg b.w.) is by the factor 10(-3) below the rhein intake of the mother.