Gastrointestinal tract drugs

In the gastrointestinal tract, drugs or toxins, as well as mechanical stimulation, induce emesis by activation of sensory receptors on afferent neurons in the vagus and sympathetic nerves. Information is relayed to the vomiting centre via the nucleus tractus solitarius... 

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). 

DRUGS ACTING ON THE GASTROINTESTINAL TRACT DRUGS USED TO TREAT INFLAMMATORY BOWEL DISEASE Infliximab... 

As patients improve clinicaUy, the route of administration should be reevaluated. Streamlining therapy from parenteral to oral (switch therapy) has become an accepted practice for many infections outside the bloodstream and CNS. Criteria that should be present to justify a switch to oral therapy include (1) overall clinical improvement, (2) lack of fever for 24 to 48 hours, (3) decreased WBC count, and (4) a functioning gastrointestinal tract. Drugs that exhibit excellent oral bioavaUabifity when compared with intravenous formulations include ciprofloxacin, clindamycin, doxycycline, gatifloxacin, levofloxacin, metronidazole, moxifloxacin, linezolid, and trimethoprim-sulfamethoxazole. 

Once absorbed from the gastrointestinal tract, drugs pass through the liver via the portal circulation and are metabolized to various extents (the first-pass effect). Following passage through the liver, the drugs are distributed to the tissues by the systemic circulation. 

Drugs that are too highly hydrophilic are often absorbed rather poorly from the gastrointestinal tract. It is sometimes possible to circumvent this difficulty by preparing esters of such compounds so as to change their water lipid partition characteristics in order to enhance absorption. Once absorbed, the esters are cleaved by the numerous esterase enzymes in the bloodstream, releasing free drug. 

PTU is also well absorbed from the gastrointestinal tract. Peak serum concentrations are in the range of 3 f.Lg/ml at 1 h after drug ingestion after an oral dose of... 

As with all drugs, the specific side effects of the quinolones must be considered when they are chosen for treatment of bacterial infections [5]. Reactions of the gastrointestinal tract and the central neivous system are the most often observed adverse effects during therapy with quinolones. It should be underlined, however, that compared with many other antimicrobials, diarrhea is less frequently observed during quinolone treatment. Antibiotic-associated colitis has been observed rarely during quinolone therapy. Similarly, hypersensitivity reactions, as observed during therapy with penicillins and other (3-lactams, is less frequently caused by quinolones. Some other risks of quinolone therapy have been defined and must be considered if a drug from this class is chosen for treatment of bacterial infections. 

DIARRHEA Diarrhea may be an indication of a super-infection of the gastrointestinal tract or pseudomembranous colitis. The nurse inspects all stools and notifies the primary health care provider if diarrhea occurs because it may be necessary to stop the drug. If diarrhea does occur and there appears to be blood and mucus in the stool, it is important to save a sample of the stool and test for occult blood using a test such as Hemoccult. If the stool tests positive for blood, the nurse saves the sample for possible further laboratory analysis. 

The cephalosporins also may be used perioperatively, that is, during the preoperative, intraoperative, and postoperative periods, to prevent infection in patients having surgery on a contaminated or potentially contaminated area, such as the gastrointestinal tract or vagina In some instances, a specific drug may be recommended for postoperative prophylactic use only. 

The most common adverse reactions seen with this drug are related to the gastrointestinal tract and may include nausea, anorexia, and occasionally vomiting and diarrhea The most serious adverse reactions are associated widi die CNS and include seizures and numbness of die extremities. Hypersensitivity reactions also may be seen. Thrombophlebitis may occur widi intravenous (IV) use of die drug. 

Because of die wide distribution of parasympadietic nerves, tiiese drugs affect many organs and structures of die body, including the eyes, die respiratory and gastrointestinal tracts, the heart, and the bladder (see Display 25-1). 

However, the normal cells that line the oral cavity and gastrointestinal tract, and cells of the gonads, bone marrow, hair follicles, and lymph tissue are also rapidly dividing cells and are usually affected by these drugs. Thus, antineoplastic drugs may affect normal as well as malignant (cancerous) cells. 

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