Environmental Variability Flashcards
What is the most important determinant of drug dose?
Body size
500 fold range in body size with a 100 fold range in maintenance dose rates
How do maintenance rates vary so little compared with body size?
Allometric scaling states the relationship between clearance and weight is non linear
How does body composition affect drugs?
Fat mass (22% or 28%) vs fat free mass Drug clearance is driven mainly by fat free mass but also fat mass
What role does renal function play in drug clearance?
Differences in renal function explains a ten fold difference in clearance
How can renal function be predicted?
Serum creatinine calculated creatinine clearance
Renal function = predicted CLcr / normal CLcr
What is the issue with hepatic function?
Difficult to predict hepatic drug clearance without administering drug
Liver function tests measure damage which is not function
Which age of a baby should be used?
Post natal age does not account for in utero maturation
Post menstrual age usually 2 weeks longer than biological age -recommended
Post conception age most accurate but not widely recorded
When is the highest clearance per kg?
2 years old
What fraction of an adult dose should a full term baby receive?
1/30
