Osmotic diarrhea

Diarrhea is a common problem that is usually self-limiting and of short duration. Increased accumulations of small intestinal and colonic contents are known to be responsible for producing diarrhea. The former may be caused by increased intestinal secretion which may be enterotoxin-induced, eg, cholera and E. col] or hormone and dmg-induced, eg, caffeine, prostaglandins, and laxatives decreased intestinal absorption because of decreased mucosal surface area, mucosal disease, eg, tropical spme, or osmotic deficiency, eg, disaccharidase or lactase deficiency and rapid transit of contents. An increased accumulation of colonic content may be linked to increased colonic secretion owing to hydroxy fatty acid or bile acids, and exudation, eg, inflammatory bowel disease or amebiasis decreased colonic absorption caused by decreased surface area, mucosal disease, and osmotic factors and rapid transit, eg, irritable bowel syndrome. 

Excessive sweating, osmotic diarrhea, vomiting, nasogastric suctioning, and respiratory... 

Osmotic diarrhea results from the intake of unabsorbable but water-soluble solutes in the intestinal lumen leading to water retention. Common causes include lactose intolerance and ingestion of magnesium-containing antacids. 

Although diarrhea can often be attributed to a specific mechanism, some patients develop diarrhea due to overlapping mechanisms. For example, malabsorption syndromes and traveler s diarrhea are associated with both secretory and osmotic diarrhea. 

Stool volume and electrolytes can be assessed in large-volume watery stools to determine whether the diarrhea is osmotic or secretory. 

Poorly absorbed substances retain intestinal fluids, resulting in osmotic diarrhea. 

Although these experiments showed growth was possible using casein hydrolysate, Rose also demonstrated that when the amino acid mixture was used rather than the intact protein, additional calories had to be provided as fat plus carbohydrate, if nitrogen balance was to be maintained. It was later shown that the carbohydrate was needed to protect the free amino acids from oxidation in the intestinal epithelium in the course of absorption. Further, amino acids are poorly tolerated by mouth, causing vomiting and/or diarrhea. After World War II attempts to feed very emaciated prisoners in concentration camps with protein hydrolysates were unsuccessful. It was then recognized that osmotic effects from the amino acids were responsible for the unpleasant consequences. 

Pharmacology Oral solution induces diarrhea (onset, 30 to 60 minutes) that rapidly cleanses the bowel, usually within 4 hours. Polyethylene glycol 3350 (PEG 3350), a nonabsorbable solution, acts as an osmotic agent. 

A variety of adverse effects have been reported following the use of antacids. If sodium bicarbonate is absorbed, it can cause systemic alkalization and sodium overload. Calcium carbonate may induce hypercalcemia and a rebound increase in gastric secretion secondary to the elevation in circulating calcium levels. Magnesium hydroxide may produce osmotic diarrhea, and the excessive absorption of Mg++ in patients with renal failure may result in central nervous system toxicity. Aluminum hydroxide is associated with constipation serum phosphate levels also may become depressed because of phosphate binding within the gut. The use of antacids in general may interfere with the absorption of a number of antibiotics and other medications. 

Mannitol is poorly absorbed by the GI tract, and when administered orally it causes osmotic diarrhea. For systemic effect, mannitol must be given parenterally. Mannitol is not metabolized and is excreted by glomerular filtration within 30-60 minutes, without any important tubular reabsorption or secretion. 

The movement of Na+ and glucose from the lumen of the intestine across the epithelial cell to the blood sets up a difference in osmotic pressure across the cell. As a result, water flows through the cell, across the apical and basolateral membranes by simple diffusion. Hence the uptake of water requires both Na+ and glucose (or amino acids) to be present in the lumen of the intestine. The presence of water alone in the lumen of the intestine is much less effective. This is the basis of glucose rehydration therapy as a remedy for dehydration a solution of glucose and salt (NaCl) is administered to the patient. This is a simple, inexpensive but extremely important treatment which has saved the lives of many infants in developing countries who would have otherwise died of the effects of dehydration, usually associated with diarrhea. 

Four general pathophysiologic mechanisms disrupt water and electrolyte balance, leading to diarrhea. These four mechanisms are the basis of diagnosis and therapy. They are (1) a change in active ion transport by either decreased sodium absorption or increased chloride secretion (2) a change in intestinal motility (3) an increase in luminal osmolarity and (4) an increase in tissue hydrostatic pressure. These mechanisms have been related to four broad clinical diarrheal groups secretory, osmotic, exudative, and altered intestinal transit. 

Well-controlled studies on aminocaproic acid in a limited number of patients showed no serious adverse effects. Minor unwanted effects have been reported in 10-20% of patients and include headache, nasal congestion, conjunctival suffusion, nausea, vomiting, diarrhea, and transient hjrpotension (32). Skin rashes have also been associated with aminocaproic acid, including maculopapular and morbilliform eruptions. Rarer dermatological reactions reported include purpuric rashes (33), bullous eruptions (34), and contact dermatitis with positive patch tests (35-37). Treatment with a high dose (the maximum daily dose is 36 g/day) can result in an osmotic diuresis (38). 

Sorbitol is slowly absorbed by passive diffusion in the small intestine. After oral administration, it increases osmotic pressure in the bowel by drawing in water, and is thus an osmotic laxative, sometimes leading to diarrhea... 

Magnesium salts, given alone or in combination with other antacids, commonly cause diarrhea of osmotic origin (10). 

Reported adverse effects include the potential for osmotic diarrhea in the elderly using antacids containing magnesium trisilicate and the potential for the formation of bladder and renal calculi following the long-term use of magnesium trisilicate as an antacid. ... 

Therapeutically, mannitol administered parenterally is used as an osmotic diuretic, as a diagnostic agent for kidney function, as an adjunct in the treatment of acute renal failure, and as an agent to reduce intracranial pressure, treat cerebral edema, and reduce intraocular pressure. Given orally, mannitol is not absorbed significantly from the GI tract, but in large doses it can cause osmotic diarrhea see Section 14. 

The cathartic effect of sulfate is mainly due to the osmotic activity of unabsorbed sulfate salts in the intestine. The laxative effect that results from sulfate is an osmotic diarrhea. Whether or not this laxative effect occurs depends on the amount of sulfate and other osmotically active materials that are present in the intestines these materials include magnesium, sodium, and some sugars. 

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