- Absorption<\/a>:\n Drug absorption does not appear to change dramatically with age. \nGenerally, changes in the rate rather than in the extent of absorption \nare found. As exceptions, marked differences in absorption are observed \nin the neonatal period and in the elderly. In both cases, a decrease in \nhepatic metabolism and first pass effect<\/a> may lead to an increase in oral bioavailability<\/a> of some drugs.<\/li>
- Distribution<\/a>: The volume of distribution<\/a>\n is frequently directly proportional to body weight and modulated by \nage. In some cases, age-related changes in drug binding can affect the \nvolume of distribution (e.g. decrease in extracellular fluid in the \nelderly).<\/li>
- Metabolism<\/a>:\n Aging clearly affects metabolism. The enzymes involved in both phase I \nand phase II metabolism mature gradually following the first two to four\n weeks following postpartum. Full maturity appears in the second decade \nof life with a subsequent slow decline in function associated with \naging. The overall decrease of metabolic clearance<\/a> is around 1 % per year.<\/li>
- Excretion<\/a>: Renal clearance<\/a>\n normalized for bodyweight is depressed in neonates but then rapidly \nincreases to reach a maximum at six months. Throughout adulthood, age is\n associated with an average decrease in renal function of 1% per year. \nBut most strikingly, age is associated to an increase in the variability\n of renal clearance among individuals.<\/li><\/ol>\n\n\n\n
![\"\"](\"https:\/\/sepia2.unil.ch\/pharmacology\/wp-content\/uploads\/2019\/06\/age.png\")
<\/figure><\/div>\n\n\n\nClinical implications<\/h3>\n\n\n\n
Adaptation of drug regimens<\/a>\n is most important for neonates, infants and in the elderly. The lack of\n maturation of renal and hepatic function in the neonates and young \ninfants necessitates that the rate of administration of drugs be \nreduced. In children, drug clearance<\/a>\n is considered to correlate better with body surface area than body \nweight. Therefore, higher maintenance dose per kilogram body weight are \nrequired the smaller and the younger the child.\n<\/p>\n\n\n\n
At the other extreme, drug use in the elderly \ngenerally requires significant reductions in drug dose reflecting the \ngeneral decline in body function with age. Therefore, increase attention\n should be given to both treatment failure and toxicity. In the elderly,\n there should be awareness of possible exaggerated pharmacodynamic \nresponses, as there may be a increase in sensitivity of target organs.<\/p>\n","protected":false},"excerpt":{"rendered":"
“Variability of pharmacokinetic parameters due to age” Description Aging is an additional source of variability in drug pharmacokinetics. This age-induced variability is considered for each of the four main pharmacokinetic mechanisms: Absorption: Drug absorption does not appear to change dramatically with age. Generally, changes in the rate rather than in the extent of absorption are … <\/p>\n
- Distribution<\/a>: The volume of distribution<\/a>\n is frequently directly proportional to body weight and modulated by \nage. In some cases, age-related changes in drug binding can affect the \nvolume of distribution (e.g. decrease in extracellular fluid in the \nelderly).<\/li>