Sunday, January 15, 2006

drug interactions

A drug interaction is defined as the effect of one drug altering the known effects of another drug. Interactions can occur between different drugs, between drugs and laboratory tests, and between drugs and food consumption. The elderly are affected by drug interactions because they often take many different drugs at one time. Drug-drug reactions may occur by changes in the absorption, distribution, metabolism, or excretion of medications. Drugs may interfere with clinical laboratory test procedures by physical or chemical means. The color of body fluids can be 78 drug reactions, adverse altered, for example, by riboflavin. False positive readings can be obtained by ascorbic acid or nalidixic acid when urine glucose levels are determined by copper-reduction methods.
Ingestion of food with drugs may alter both the extent and the rate of drug absorption. Food changes the amount of secretion of gastric acid, digestive enzymes, and bile, thus altering the rate of absorption. Drug metabolism can be affected by charcoal broiled foods, for example. Urinary pH can alter the effects of a drug. Acidic drugs are excreted more rapidly in a basic urine and more slowly in an acid urine. Conversely, the excretion of basic drugs is enhanced in an acid urine and delayed in a basic urine.
Covington, T., and Walker J. Current Geriatric Therapy. Philadelphia: W. B. Saunders, 1984.


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