THE UNIVERSITY OF AUCKLAND
MID-SEMESTER TEST
2015
MEDSCI 303
Principles of Pharmacology
(Time Allowed: 45 minutes)
NOTE: Answer ALL of the following questions (Total marks = 40)
USE A SEPARATE ANSWER BOOKLET FOR EACH QUESTION
MEDSCI 303
1.
C o n t r a c t ile r e s p o n s e ( g )
a) Write brief notes about the differences between competitive reversible, competitive irreversible and noncompetitive antagonism, giving drug examples where appropriate.
(6 marks)
10
D r u g A A lo n e
8
D ru g A + D ru g B
( 1 x 1 0 -7 M )
6
4
2
0
-8
-6
-4
-2
lo g [ A g o n is t] , M
Above is a concentration-response curve obtained from an organ bath experiment similar to the one conducted in
Lab 2 – Potency of Agonists and Antagonists.
b) Based on the data, what type of drug (i.e. type of agonist or antagonist) does Drug B appear most likely to
be? Explain your answer and provide an example of this type of drug.
(3 marks)
c) What other types of agonist or antagonist could it be? Explain your answer(s).
(4 marks)
d) If possible and appropriate for Drug B, calculate:
i. pA2
ii. pD2’
If either of these calculations are not possible or relevant, explain why not.
(4 marks)
e) When the concentration of Drug A alone was increased from 1x10-5 M to 1x10-4 M the response decreased
from 6.8 g to 6.15 g. What is the most likely explanation for this decrease? Briefly explain how this occurs?
(3 marks)
MEDSCI 303
2.
A nursing mother has a life-threatening infection and is treated with an antibiotic testastatin. The drug is weak
base (pKa = 8.4) and is available either as an intravenous preparation, or 500 mg capsules with 66 % oral
bioavailability.
The pharmacokinetic parameters for this patient are: plasma clearance 8 L/h; volume distribution 160 L; and the
target concentration is 3.3 mg/L:
a)
Calculate the infusion rate required to achieve the plasma target concentration.
(2 marks)
b)
How long (in hours) will it take to achieve this steady-state concentration?
(3 marks)
c)
If you wished to achieve this steady-state very rapidly, what would you do?
(3 marks)
As the patient’s condition improves, it is decided to switch to an oral regimen, but it is essential to maintain the
plasma concentration within the therapeutic range, 2-6 mg/L.
d)
Calculate an appropriate oral dose regimen to maintain the mean steady-state at about 3.3 mg/L, but
with peaks and troughs within the therapeutic range.
(4 marks)
During this oral regimen, the mother commences breast feeding and the baby consumes 0.8 L/day of mother’s
milk.
e)
Calculate the % of the mothers total daily dose that the baby will ingest per day
(assume, plasma pH = 7.4, and milk pH = 6.4; mum’s Css = 3.3 mg/L)
(8 marks)
[Show all calculations and where appropriate explain your answers]