Pharmacologic changes with aging
| Pharmacologic concern | Change with normal aging | Common disease effects |
|---|---|---|
| Gastrointestinal absorption or function | Slowing of gastrointestinal transit time may prolong effects of continuous-release enteral drugs Opioid-related bowel dysmotility may be worse in older patients | Disorders that alter gastric pH may reduce absorption of some drugs Surgically altered anatomy may reduce absorption of some drugs |
| Transdermal absorption | Under most circumstances, there are few changes in absorption with age, and differences in absorption may relate more to different patch technology used | Temperature and other specific patch technology characteristics may affect absorption |
| Distribution | Increased fat-to-lean body weight ratio may increase volume of distribution for fat-soluble drugs | Aging and obesity may result in longer effective drug half-life |
| Liver metabolism | Oxidation is variable and may decrease, resulting in prolonged drug half-life Conjugation is usually preserved First-pass effect usually unchanged Genetic enzyme polymorphisms may affect some cytochrome enzymes | Cirrhosis, hepatitis, and tumors may disrupt oxidation but not usually conjugation |
| Renal excretion | Glomerular filtration rate decreases with age in many patients, which results in decreased excretion | Chronic kidney disease may predispose further to renal toxicity |
| Active metabolites | Reduced renal clearance will prolong effects of metabolites | Renal disease Increase in half-life |
| Anticholinergic side effects | Increased confusion, constipation, incontinence, movement disorders | Enhanced by neurologic disease processes |
Reprinted from American Geriatrics Society Panel on Pharmacological Management of Persistent Pain in Older Persons. Pharmacological management of persistent pain in older persons. J Am Geriatr Soc 2009; 57:1331–1346.