Drugs That Affect the Gastrointestinal System

Helicobader pylori hydrochloric acid hypersecretory paralytic ileus photophobia proton pump inhibitor 

I he gastrointestinal (GI) tract is subject to more diseases and disorders than any other system of the body. Some drugs used for GI disorders are available as nonprescription drug, thereby creating the potential problems of misuse and overuse of the drugp and the disguising of more serious medical problems. 

Some of the cells of the stomach secrete hydrochloric acid, a substance that aids in the initial digestive process. 

SUM MARY DRUG TABLE DRUGS USED IN THE MANAGEMENT OF GASTROINTESTINAL DISORDERS 

Nausea, diarrhea, abdominal cramps, H. pylori with duodenal ulcer Ulcerative colitis 

The dru presented in this ch )ter include the antacids, anticholinergics, GI stimulants, proton pump inhibitors, histamine H2 antagonists, antidiarrheals, antiflatulents, digestive enzymes, emetics, gallstone-solubilizing dru, laxatives, and miscellaneous dru. Some of the more common preparations are listed in the Summaiy Drug Table Dni Used in tlie Man ement of Gastrointestinal Disorders. 

Antacids (gainst acids) are dru tliat neutralize or reduce die acidily of stomach and duodenal contents by combining with hydrodiloric acid and producing salt and water. Elxampl of antacids include aluminum hydroxide gel (Amphojel), magaldrate (Riopan), and m iesia or m iesium hydroxide (Milk of M nesia). 

Antacids are used in die treatment of hyperacidity, such as heartburn, gastroesoph eal reflux, sour stomach, acid indigestion, and in the medical treatment of peptic ulcer. Many antacid preparations contain more than one ingredient. An additional use for aluminum carbonate is in die treatment of hyiDeqihosphatemia or for use widi a low phosphate diet to prevent formation of phosphate urinaiy ston. Clalcium carbonate may be used in treating calcium deficiency states such as menopausal osteoporosis. M nesium oxide may be used in the treatment of m nesium deficiencies or m nesium depletion from malnutrition, restricted diet, or alcoholism. 

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Chapter 48 Drugs That Affect the Gastrointestinal System... 

Unit VIII lias been expanded to cover drugs that affect both the gastrointestinal and urinary systems. The unit consists of three chapters uretics, urinary anti-infectives and miscellaneous urinary drugp, and drag s that affect the gastrointestinal system. 

Pathophysiologically, constipation generally results from disordered colonic transit or anorectal function as a result of a primary motility disturbance, certain drugs, or in association with a large number of systemic diseases that affect the gastrointestinal tract. Constipation from any cause may be exacerbated by chronic illnesses that lead to physical or mental impairment and result in inactivity or physical immobility. Additional contributing factors may include a lack of fiber in the diet, generalized muscle weakness, and possibly stress and anxiety. 

During its many years of use as a consumer product, carbon tetrachloride compiled a grim record of toxic effects that led the U.S. Food and Drug Administration (FDA) to prohibit its household use in 1970. It is a systemic poison that affects the nervous system when inhaled, and the gastrointestinal tract, liver, and kidneys when ingested. The biochemical mechanism of carbon tetrachloride toxicity involves reactive radical species, including... 

Absorption is the transfer of a drug from its site of administration to the blood stream. The rate and efficiency of absorption depend on the route of administration. For intravenous delivery, absorption is complete, that is, the total dose of drug reaches the systemic circulation. Drug delivery by other routes may result in only partial absorption and thus lower bioavailability. For example, the oral route requires that a drug dissolve in the gastrointestinal fluid and then penetrate the epithelial cells of the intestinal mucosa disease states or the presence of food may affect this process. 

Figure 2.1 Oral drag absorption process from the gastrointestinal tract (GIT). Schematic depicting the three major processes (/a, / and /h) affecting absorption of drug from the site of administration to the systemic circulation, that is oral bioavailability, /a- fg, and /h can be estimated from the general relationship provided in Eq. 2.3 ...

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