Problem Set –2005 -- Due 2/22/05
1. Amphetamine is a weak base with a pKa of 9.8. Draw a graph of the
relationship between pH and the ratio of ionized to unionized amphetamine
(remember the Henderson-Hasselbalch equation for bases). Assume that a
victim of amphetamine overdose has a urine pH of 7.0. Would altering her
urine pH increase the renal clearance of the drug? What if the pKa of the
poison were 7.0?
2. Two new intravenous anesthetic drugs, A and B, are being screened in
rats. After administration of 10 mg, both drugs produce nearly identical
effects: The animals become unresponsive within 30 sec. and awaken 15-20
min later. The graph below shows the plasma drug concentrations vs time
obtained during this experiment.
• How would you describe the pharmacokinetics of these compounds? Can
you characterize the clearances, volumes of distribution, etc.?
• Why do they both last for only 15-20 min?
• How are the compounds pharmacokinetically different? What
implications could this have for the clinical use of the drugs?
0 180 360 540 720
Time (Min)
0.1
1
10
100
500
Concentration (ng/ml)
A
B
3. Pindolol is a partial agonist at β receptors. How can it act as an
antagonist?
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