Preventing Polypharmacy in Older Adults

Kathleen Woodruff MS, CRNP


Am Nurs Journal. 2010;5(10) 

In This Article

How Aging Affects Response to Drugs

Older persons react differently to medications than younger persons. Although absorption rates for most drugs don't change with age, aging alters body fat and water composition: fat stores increase while total body water decreases. These changes can alter therapeutic drug levels, causing greater concentrations of water-soluble drugs and longer half-lives of fat-soluble drugs.

Also, because the liver metabolizes many drugs, such age-related changes as reduced hepatic blood flow and liver size alter drug clearance. Drug elimination also may be affected by age-related decreases in renal blood flow, kidney size, and glomerular filtration rates, as well as changes stemming from chronic diseases.

Additionally, digoxin and certain other drugs are bound to plasma proteins so that only the unbound or free portion of the drug is biologically active. Therefore, decreases in serum albumin levels—common in older adults with chronic illnesses, malnutrition, or severe debilitation—can lead to higher drug blood levels. Subsequently, older patients may be more sensitive to some drugs and less sensitive to others.