A variety of drugs and toxins can produce severe abdominal pain and, in some cases, a surgical abdomen. Toxins can be classified according to mechanisms of injury: 1. Corrosives often produce severe gastroenteritis and may result in gastric or esophageal perforations. Examples of corrosive substances include aspirin, iron, mercury, acids and alkali. 2. Drugs may cause intestinal ileus or obstruction by pharmacologic actions (i.e., anticholinergic drugs and narcotics) or by mechanical obstruction (charcoal and drug bezoars). 3. Abdominal pain simulating an acute abdomen may result from systemic effects of black widow spider envenomation or intoxication with heavy metals such as lead and arsenic. 4. Ischemic bowel disease may occur from use of vasoconstrictor drugs, such as ergotamines, amphetamines and cocaine, or may follow treatment with catecholamines or digitalis in critically ill patients. Small bowel ischemia is life-threatening and may require bowel resection. 5. Many drugs cause abdominal pain by directly injuring abdominal organs, such as the liver and pancreas. Antibiotic-associated colitis may present with abdominal pain and inflammatory diarrhea. Consideration of drugs and toxins plays an important role in the differential diagnosis of the acute abdomen.