Colonic toxicity of administered drugs and chemicals.

Although uncommon, medication-induced colonotoxicity is important to recognize because medication cessation generally leads to prompt clinical improvement, while medication continuation results in disease exacerbation. This review categorizes the association between medications and colonotoxicity as "well-established" or "probable," according to the following criteria: total number of reported cases, number of different research groups reporting an association, experimental and pharmacologic evidence of an association, and validity of an association in each reported case. Cocaine, ergotamine, estrogen, sodium polystyrene, alosetron, amphetamines, pseudoephedrine, and vasopressin are associated with colonic ischemia. The mechanisms include vasospasm, thrombogenesis, and shunting of blood from mesenteric vessels. Narcotics, phenothiazines, vincristine, atropine, nifedipine, and tricyclic antidepressants are associated with colonic pseudo-obstruction. The mechanisms include antagonizing prokinetic neurotransmitters, stimulating antikinetic neurotransmitters, promoting dysmotility, relaxing smooth muscle, and injuring enteric neurons. Numerous antibiotics are associated with pseudomembranous colitis; ampicillin is associated with hemorrhagic colitis; chemotherapy is associated with neutropenic colitis; and deferoxamine is associated with Yersinia enterocolitis. Mechanisms of these toxicities include altering normal bowel flora, weakening immunologic defenses, promoting microorganism virulence, and mucosal injury. Gold compounds, nonsteroidal antiinflammatory drugs, alpha-methyldopa, salicylates, and sulfasalazine are associated with an inflammatory or cytotoxic colitis. The mechanisms include direct mucosal cytotoxicity, antimetabolite effects, or drug allergy. Nonsteroidal antiinflammatory drugs, cyclo 3 fort, flutamide, lansoprazole, and ticlopidine are associated with lymphocytic colitis. The mechanisms include immunologic activation or attenuated immunologic defenses. Chronic cathartic use leads to colonic hypomotility and abdominal distention. Intrarectally administered corrosive compounds can produce a toxic colitis.