Effects of Age on Pharmacokinetics Flashcards
Define neonate
Between 0 - 27 days of life
How is corrected age worked out?
Chronological age - prematurity
Define Infant?
28 days - 1 year
Define child.
1 - 18 years
What is chronological age?
Age from birth to current age
What is gestational age at brith?
The length of pregnancy from the first day of mother’s last menstrual cycle to birth date.
What is the definition for post menstrual age?
Gestational age + chronological age
How is the corrected age for pre-term neonates worked out?
Chronological age - degree of prematurity
If born 3 weeks early, When chronological age is 7 weeks, corrected age is 4 weeks
What is the % drug distribution in fats in neonates?
10%
What is the % drug distribution in fats in adults?
25 - 30%
What is the % drug distribution in water for neonates?
70 - 80% water of total body weight
What is the % drug distribution in water for adults?
50 - 60 % water of total body weight
What is the concentration of plasma proteins on neonates compared to adults?
Plasma protein concentrations are lower in neonates and children compared to adults
EXTRA: More likely to lead to saturation of drug binding sites
What age are full adult levels reached for phase 1 reactions? (Cytochrome p450 enzymes)
1 to 2 years
some are undetectable at birth
Others are at 30% of adult levels
What age are full adult levels reached for phase 2 reactions?
Variable rates of maturation
Glucurnyl transferase enzymes:
- some achieve adult levels at 6 months
- others take a decade to develop
Acetylation is under developed at birth
Sulfation processes are already well established
What age are adult rates reached in terms of renal function?
Adult rates are reached towards the end of the first year of life.
Excretion is dependent on GFR, Tubular secretion and reabsorption
(mostly under developed at birth, especially prematures)
What happens to central body fat and total body water with age?
Total body water reduces with age
Central body fat increases
What happens to drug elimination with age (in terms of real and hepatic function)?
Renal function decreases with age, resulting in reduced excretion of drugs
Hepatic function
30-60% reduction in blood flow and liver volume by age 90
Phase 1 drug reaction are affected more than phase 2 processes.
What are the effects of drug dosing with age?
Instead of age focused drug dosing, organ function is measured.
For example the effects of benzodiazepines are more sensitive with age
What happens to the volume of distribution for hydrophilic and lipophilic drugs with age?
Hydrophilic drugs Decreases
Lipophilic drugs Increases
