Effects of Age on Pharmacokinetics

Question 1

Define neonate

Answer 1

Between 0 - 27 days of life

Question 2

How is corrected age worked out?

Answer 2

Chronological age - prematurity

Question 3

Define Infant?

Answer 3

28 days - 1 year

Question 4

Define child.

Answer 4

1 - 18 years

Question 5

What is chronological age?

Answer 5

Age from birth to current age

Question 6

What is gestational age at brith?

Answer 6

The length of pregnancy from the first day of mother’s last menstrual cycle to birth date.

Question 7

What is the definition for post menstrual age?

Answer 7

Gestational age + chronological age

Question 8

How is the corrected age for pre-term neonates worked out?

Answer 8

Chronological age - degree of prematurity

If born 3 weeks early, When chronological age is 7 weeks, corrected age is 4 weeks

Question 9

What is the % drug distribution in fats in neonates?

Answer 9

10%

Question 10

What is the % drug distribution in fats in adults?

Answer 10

25 - 30%

Question 11

What is the % drug distribution in water for neonates?

Answer 11

70 - 80% water of total body weight

Question 12

What is the % drug distribution in water for adults?

Answer 12

50 - 60 % water of total body weight

Question 13

What is the concentration of plasma proteins on neonates compared to adults?

Answer 13

Plasma protein concentrations are lower in neonates and children compared to adults

EXTRA: More likely to lead to saturation of drug binding sites

Question 14

What age are full adult levels reached for phase 1 reactions? (Cytochrome p450 enzymes)

Answer 14

1 to 2 years

some are undetectable at birth
Others are at 30% of adult levels

Question 15

What age are full adult levels reached for phase 2 reactions?

Answer 15

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

Question 16

What age are adult rates reached in terms of renal function?

Answer 16

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)

Question 17

What happens to central body fat and total body water with age?

Answer 17

Total body water reduces with age

Central body fat increases

Question 18

What happens to drug elimination with age (in terms of real and hepatic function)?

Answer 18

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.

Question 19

What are the effects of drug dosing with age?

Answer 19

Instead of age focused drug dosing, organ function is measured.

For example the effects of benzodiazepines are more sensitive with age

Question 20

What happens to the volume of distribution for hydrophilic and lipophilic drugs with age?

Answer 20

Hydrophilic drugs Decreases

Lipophilic drugs Increases