Management of antibiotic-associated pseudomembranous colitis

The diagnosis, etiology, epidemiology, and drug therapy of antibiotic-associated pseudomembranous colitis (AAPMC) are reviewed. AAPMC is an uncommon but potentially serious adverse reaction to therapy with almost any oral or injectable antibiotic and certain antineoplastic agents that alter intestinal flora. Proliferation of Clostridium difficile and subsequent release of clostridial cytotoxins cause pseudomembranous lesions and symptoms such as watery diarrhea, cramping abdominal pain, and low-grade fever. Symptoms can appear from four days after the start of antibiotic or antineoplastic therapy to 10 weeks after therapy has been discontinued. Drug therapy of AAPMC is directed at reducing the amount of Cl. difficile in the colon and promoting normalization of intestinal flora. Mild cases of AAPMC may respond to discontinuation of the etiologic agent and replacement of fluid and electrolytes. Therapy with an anticlostridial antibiotic is indicated in severe cases; although a seven- to 10-day course of oral vancomycin hydrochloride is the most widely recognized therapy, the drug is expensive and unpalatable. Good results have been reported with oral metronidazole and with bacitracin, both of which are less expensive than vancomycin. For all of these therapies, relapse rates are 20-39%. Anion exchange resins may be useful in mild cases of AAPMC. Successful management of AAPMC depends on a complex and ill-defined interrelationship between normal intestinal flora, patient immune response, antibiotic therapy, and the infecting clostridium strain. For moderate or severe cases of AAPMC, therapy should begin with metronidazole or bacitracin and vancomycin should be reserved for refractory cases, relapses, or patients with allergies to the other agents.