Anthraquinones melanosis coli

Most of the concerns with the use of diphenylmethane derivatives apply to the anthraquinone derivatives. In addition, the anthraquinone derivatives may cause melanosis coli, an accumulation of dark pigment, mainly in the cecum and rectum, that is evident after 4 to 13 months of use. A pathologic effect of melanosis coli has not been demonstrated, and it appears to be reversible after anthraquinones have been discontinued for 3 to 6 months. 

Melanosis coli is observed in 12-31% of unselected constipated patients. A causal relationship between melanosis coli and use of anthraquinone laxatives has been shown in animals and humans. Sennosides produce melanosis coli after 4—13 mo of use, which disappears 5-11 mo after cessation of sennoside use. Melanosis coli begins abruptly at the ileocolonic junction and may extend to the dentate line. The intensity is highest in the cecum and becomes less intense in the aboral direction, and may increase again in the rectum, with a prevalence of 1-8% on proctoscopy. The pigment has not been definitively identified, but it is probably lipofuscin. Even if melanosis coli cannot be seen... 

A prospective cohort study of the risk of anthraquinone laxatives use for the development of colorectal neoplasms indicated no statistically significant risk of anthranoid use for the development of colorectal adenomas or carcinomas. Macroscopic and high-grade microscopic melanosis coli were not significant risk factors for the development of adenomas or carcinomas (Nusko et al. 2000). 

Gastrointestinal A 74-year-old woman developed severe melanosis coli of the whole colon after using anthraquinone laxatives over many decades [72 ]. Endoscopy showed marked black pigmentation of the colonic mucosa, which was confirmed by histology as widespread lipofuscin granulation. Several adenomatous lesions were found, although no colorectal cancer was detected. 

Abendroth A, Klein R, Schlaak J, Metz KA, Dobos GJ, Langhorst J. Impressive picture of a melanosis coli after chronic anthraquinone laxative use—is there an increased risk for colorectal cancer Z Gastroenterol 2009 47 579-82. 

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