Motility, gastrointestinal, drugs affecting

A summary of how physiological factors affect the dissolution rate is given in Table 21.2. The effective surface area will be affected by the wetting properties of the bile acids and other surface-active agents in the gastrointestinal tract. The dif-fusivity of a drug molecule in the intestinal juice will be altered by changes in viscosity that are induced, for instance, by meal components. An increased dissolution rate could be obtained at more intense intestinal motility patterns or increased... 

The gastrointestinal absorption of drugs may be affected by concurrent use of other agents that (1) have a large surface area upon which the drug can be adsorbed, (2) bind or chelate, (3) alter gastric pH, (4) alter gastrointestinal motility, or... 

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. 

Table 1 Factors affecting drug absorption from the colon Physical characteristics of drug (pkTa> degree of ionization) Colonic residence time as dictated by gastrointestinal tract motility...

Antiepileptics e.g. Phenytoin Increase in gastrointestinal motility caused by cisapride may affect the rate and/or extent of absorption, which may be important for some drugs with a narrow therapeutic index, such as some antiepileptics. However, no available case reports to suggest this is a problem, and one case reporting no interaction. Uncertain. Monitor antiepileptic drug levels as usual practice. Advise the patient to report any increase in adverse effects. 1,7... 

ANTIEMETICS AND DRUGS THAT AFFECT GASTROINTESTINAL MOTILITY [SEDA-31, 573 SEDA-32, 665 SEDA-33, 741]... 

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