decline in organ function occurs when advancing age, drug therapy in older adults is most likely to result in adverse effects and toxicity, high use of medications, polypharmacy, noncompliance, nonadherence, increased incidence of chronic illnesses, sensory and motor deficits, gastric pH less acidic, gastric emptying and movement through GI tract slowed, blood flow to GI tract reduced, absorptive surface of GI tract reduced, lower total body water percentages, increased fat content, decreased production of proteins by the liver, aging liver produces fewer microsomal enzymes (affects drug metabolism), reduced blood flow to liver, decreased glomerular filtration rate, decreased number of nephrons, drugs are cleared less effectively