[Undesirable colorectal effects of drugs].

The most severe adverse reactions associated with medicinal treatment of the colon involve pseudomembranous colitis following antibiotic treatment, notably with clindamycin, lincomycin and betalactamine. The frequency of this adverse reaction is poorly defined: 1 per 100 to 1 per 5 000 treatments depending on the study. Lesions are explained by the cytotoxic effect of Clostridium difficile toxin. Necrotizing anorectitis has been seen in cases of abuse of suppositories containing propoxyphene. The mechanism involved is still unknown.