Age, weight, and gender
16 important questions on Age, weight, and gender
What are characteristics of drug absorption in perspective of age, gender and weight?
- There is a higher stomach pH in neonates and in the elderly
- However, no great changes in absorption.
What are characteristics of drug distribution in perspective of age, gender and weight?
- The volume of distribution (L/kg) is fairly constant except in newborn (because of more extracellular water) and in obese (because lipophillic drugs distribute into fatty tissue)
How does the percentage of extracellular water change in age?
The extracellular is highly age-dependent:
newborn: 45%
children 2 years: 30%
children 4 years: 20%
adults : 15%
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What are characteristics of elderly patients in perspective to the drug distribution?
- body water is decreased with 10-15%
So, there is an increase of serum concentration of water soluble drugs, there is an decrease of serum concentration of fat soluble drugs and there is an increase of half life of fat soluble drugs.
What are characteristics of drug metabolism with respect to age, weight and gender?
- There is a gradually decline from the age of 30-50
- It is related to the maturation (early childhood) of liver and gradual decline of cardiac output (> 40 years of age)
- It is influenced by hepatic disease.
How is the drug metabolism by CYP3A enzymes during life?
How is the midazolam clearance by Cyp3A4?
How is the renal function after birth?
What is the normal creatinine clearance at the age of 20?
What kind of functions decrease from the young adults phase on?
- cardial index
- vital capacity
- renal plasma flow
- maximal inhalation capacity
How is the renal function in children < 6 months?
- They have also an underdeveloped liver function
- Note: drugs can also be administered via breast milk.
What is allometric scaling?
- It is traditionally use to translate an animal dose to an human dose.
What are features of allometric scaling?
- As a result is the half life in children shorter than in adults. Therefore the dosing interval must become shorter/ more frequent dosing.
How is the drug clearance in children?
- Therefore it is better to do it per m2 body surface (BSA body surface area)
- The BSA of an adult is around 1.8m2 and an adolescent has a BSA of around 1.73m2.
What are differences between children and adults about the dosage?
The dosage in mg/kg is larger in children compared to adults.
How is the drug clearance in adults?
- For young adults the GFR is around 120 ml/min
- For standard patient 60 year it is around 80 ml/min
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