Because most cases of acute gastroenteritis are self-limited, specific treatment is not necessary. Strict personal hygiene should be practiced during the illness. Some studies have quantified that only 10% of cases require antibiotic therapy. The main objective is adequate rehydration and electrolyte supplementation. This can be achieved with either an oral rehydration solution (ORS) or intravenous solutions (eg, isotonic sodium chloride solution, lactated Ringer solution). Note the following: Oral rehydration is achieved by administering clear liquids and sodium-containing and glucose-containing solutions. A simple ORS may be composed of 1 level teaspoon of salt and 4 heaping teaspoons of sugar added to 1 liter of water. The use of ORS has reduced the mortality rate associated with cholera from higher than 50% to less than 1%. ORS also is indicated in other dehydrating diarrheal diseases. ORS promotes cotransport of glucose, sodium, and water across the gut epithelium, a mechanism unaffected in cholera. The World Health Organization (WHO) recommends a solution containing 3.5 g of sodium chloride, 2.5 g of sodium bicarbonate, 1.5 g of potassium chloride, and 20 g of glucose per liter of water. Intravenous solutions are indicated in patients who are severely dehydrated or who have intractable vomiting. Absorbents (eg, Kaopectate, aluminum hydroxide) help patients have more control over the timing of defecation. However, they do not alter the course of the disease or reduce fluid loss. Note the following: An interval of at least 1-2 hours should elapse when using other medications with absorbents. Antisecretory agents, such as bismuth subsalicylate (Pepto-Bismol), may be useful. The dose is 30 mL every 30 minutes, not to exceed 8-10 doses. Antiperistaltics (opiate derivatives) should not be used in patients with fever, systemic toxicity, or bloody diarrhea or in patients whose condition either shows no improvement or deteriorates. Diphenoxylate with atropine (Lomotil) is available in tablets (2.5 mg of diphenoxylate) and liquid (2.5 mg of diphenoxylate/5 mL). The initial dose for adults is 2 tablets 4 times a day (ie, 20 mg/d). The dose is tapered as diarrhea improves. Loperamide (Imodium) is available over the counter as 2-mg capsules and as a liquid (1 mg/5 mL). It increases the intestinal absorption of electrolytes and water and decreases intestinal motility and secretion. The dose in adults is 4 mg initially, followed by 2 mg after each diarrhea stool, not to exceed 16 mg in a 24-hour period. If symptoms persist beyond 3-4 days, the specific etiology should be determined by performing stool cultures. If symptoms persist and the pathogen is isolated, specific treatment should be initiated. Empiric treatment should be initiated in patients with suspected traveler s diarrhea or dysenteric or systemic symptoms. Treatment with an agent that covers Shigella and Campylobacter organisms is reasonable in patients with diarrhea ( 4 stools/d) for more than 3 days and with fever, abdominal pain, vomiting, headache, or myalgias. A 5-day course of a fluoroquinolone (eg, ciprofloxacin 500 mg PO bid, norfloxacin 400 mg PO bid) is the first-line therapy. TMP/SMX (Bactrim DS 1 tab qd) is an alternative therapy, but resistant organisms are common in the tropics. Infection with either V cholerae or V parahaemolyticus can be treated either with a fluoroquinolone or with doxycycline (100 mg PO bid). In the absence of dysentery, do not administer antibiotics until a microbiologic diagnosis is confirmed and E coli O157:H7 is ruled out. Diet During episodes of acute diarrhea, patients often develop an acquired disaccharidase deficiency due to washout of the brush-border enzymes. For this reason, avoiding milk, dairy products, and other lactose-containing foods is advisable.