Clinical Pharmacology Chapter 304. With aging, total body water and lean body mass are reduced, and body fat is increased. Increased fat increases the volume of distribution for lipophilic drugs and may increase their elimination half-lives. Serum albumin decreases and 1 -acid glycoprotein increases, but the clinical effect of these changes on serum drug binding is unclear. In a patient with acute disease or malnutrition, sudden decreases in serum albumin may enhance drug effects because serum concentrations of unbound drug are increased.
Many drugs produce active metabolites in clinically relevant concentrations.
Serum creatinine levels remain within normal limits because older persons have less lean body mass and produce less creatinine. Decreases in tubular function parallel those in glomerular function. Because renal function is dynamic, maintenance doses of drugs should be adjusted when a patient becomes acutely ill or dehydrated or has recently recovered from dehydration. In addition, because renal function continues to decline, the dose of drugs given long-term should be reviewed periodically. All rights reserved.