Gastrointestinal tract fluid processing

During normal processes, approximately 9 liters of fluid traverse the gastrointestinal tract daily. Of this amount, 2 liters represent gastric juice, 1 liter is saliva, 1 liter is bile, 2 liters are pancreatic juice, 1 liter is intestinal secretions, and 2 liters are ingested. Of these 9 L of fluid presented to the intestine, only about 150 to 200 mL remain in the stool after reabsorptive processes occur. 

Orai Administration The oral route is the most common way of administering a drug. For a drug to be absorbed into the bloodstream, it has to be soluble in the fluids of our gastrointestinal tract. Drugs are often formulated with excipients (components other than the active drug) to improve manufacturing and dissolution processes (see Section 5.6). 

In the normal adult, 7-8 litres of of water and electrolytes are secreted daily into the gastrointestinal tract. This, together with dietary fluid, is absorbed by epithehal cells in the small and large bowel. Water follows the osmotic gradients which result from shifts of electrolytes across the intestinal epithelium, and sodium and chloride transport mechanisms are central to the causation and management of diarrhoea, especially that caused by bacteria and viruses. The energy for the process is provided by the activity of Na /K ATPase. 

About 85% of the body s phosphate occurs in bones, with 14% in soft tissues and about 1.0% in the extracellular fluids. The normal range of phosphate intake is 20 to 50 mmol/day (0.6-1.5 g phosphorus/day). Phosphate is absorbed throughout the small intestines. In the duodenum, it is absorbed by an Na-dependent transport mechanism. Here, transport of the phosphate is coupled with ttie cotransport of a sodium ion. The rate of Na-dependent transport of phosphate is enhanced by 1,25-(0H)2D3. Phosphate transport in the jejunum and ileum occurs by a passive mechanism. The rate of phosphate transport in this case is dependent mainly on the concentration of phosphate in the lumen and is independent of the levels of other nutrients and independent of energy-using processes. About 200 mg of phosphorus is excreted per day in fluids of the gastrointestinal tract. About two-thirds of this phosphorus is reabsorbed by the gut. 

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