What are the physiologic changes that occur in the elderly?
CHANGES | EFFECT | EFFECT ON DRUG USE | |
|---|---|---|---|
| General | Increased body fat Decreased total body water Decreased muscle mass | Increased V d for lipophilic drugs Decreased V d for hydrophilic drugs | Lipophilic: Delayed onset of action Prolonged half life Hydrophilic: Increased plasma levels Higher frequency of ASEs |
| Cardiovascular | Decreased cardiac index | Rapid and high drug peak | Increased toxicity risk |
| Gastrointestinal | Altered secretions Decreased gastric emptying Decreased gastric acid secretion Decreased splanchnic blood flow Decreased absorptive capacity | Increased transit time Decreased drug absorption | Altered oral bioavailability |
| Liver | Decreased liver blood flow Decreased liver mass Decreased protein synthesis Decreased hepatic enzyme function | Decreased serum albumin Decreased first pass metabolism Decreased liver clearance | Increased bioavailability of drugs with extensive first pass metabolism Decreased bioavailability of prodrugs requiring activation by liver Increased toxicity risk Decreased clearance of high extraction ratio drugs |
| Renal | Decreased GFR Decreased renal blood flow Decreased size | Decreased renal clearance | Dose adjustment |
| Nervous system | Decreased cerebral blood flow Decreased neurotransmitters Neuronal atrophy Altered receptor density/affinity | Decreased descending inhibitory pain control Altered pain processing | Altered response to pain Increased pain with noxious stimuli Altered response to CNS/PNS drugs |
ASEs , Adverse side effects CNS , central nervous system; GFR , glomerular filtration rate; PNS , peripheral nervous system; V d , volume of distribution.Rastogi R, Meek BD. Management of chronic pain in elderly, frail patients: finding a suitable, personalized method of control. Clin Interv Aging . 2013:37, Web.
