PHA 5127 problems_excretion.doc 1
PHA 5127
Problem Set "Excretion"
1. Mark true or false. A renal clearance of 500 ml /min may suggest that:
T Fthe drug is eliminated only by glomerular filtration
T F the drug is eliminated by tubular secretion
T F drug interactions in renal tubules are likely
T Fthe drug is probably nonionized
T Fthe drug is extensively reabsorbed in renal tubules
2. Drug addicts sometimes abuse amphetamines in combination with sodium
bicarbonate. What is the rationale of this emperically discovered interaction?
What could be done to enhance the detoxification of an overdosed addict?
Answer:
Amphetamines are weak bases and undergo tubular reabsorption which is pH-dependent.
Sodium bicarbonate increases the pH causing slower elimination (more drug is in
unionized form and more will be reabsorbed). To enhance detoxification during overdose,
ammonium chloride is given as it decreases the pH (less unionized form, less reabsorption)
resulting in faster elimination.
3. Which of the following factors does NOT influence glomerular filtration:
a) molecular size
b) protein binding
c) lipid solubility
d) number of functioning nephrons
e) renal blood flow
Answer:
c) lipid solubility
