Download 03_DrugEffectAnswers

ANSWERS
Process of Science
What Factors Determine the Effectiveness of Drugs?
Lab Notebook
Results
NE
NES
SE
SES
GE
GES
LE
LES
Group A
2
2
3
3
27
2
1
0
Group B
1
2
1
2
1
2
25
6
Group C
2
1
28
5
1
1
1
1
Group D
30
6
0
0
0
0
2
2
Questions
1. Many medicines can only be stored for a certain period of time, and then they must be
disposed. Hypothesize why aging can affect a drug's ability to work.
Aging causes the drug to decay the same way some foods spoil. Oxygen in the air is
usually what causes drug decay. Oxygen changes the chemistry and even the shape of the
drug, preventing it from having the proper pharmacodynamics.
2. Hypothesize why many drugs lose their effectiveness quicker if a person drinks lots of
coffee, tea, or water while taking a drug.
The caffeine in coffee and tea stimulates the kidneys to excrete water, resulting in
premature loss of the drug. Too much water also causes more drug clearance by making
the kidneys remove the excess water.
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Copyright © 2010 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
3. The dosages for certain drugs given to epileptic patients are different for females and
males. Propose an explanation for this medical practice.
The pharmacogenetic differences between females and males determine the dosage.
Factors may include the higher body fat content of females, differences in drug clearance
ability, and/or hormone differences.
4. What general observation can you make about the effect of the drug produced by the
plant?
For 29 of the 40 patients (almost 75 percent), the drug produced by the plant had a greater
effect as an antidepressant than the synthesized reboxetine.
5. What general observation can you make about the effect of the drug produced by the
genetically engineered yeast?
For 31 of the 40 patients (over 75 percent), the drug produced by the genetically
engineered yeast had less effect as an antidepressant than the synthesized reboxetine.
6. What general observation can you make about the results for group C?
For 33 of the 40 patients (over 80 percent), the effect as an antidepressant was the same
as for their previously prescribed synthesized reboxetine, which is not surprising because
that is exactly what they were given.
7. What general observation can you make about the results for group D?
For 36 of the 40 patients (90 percent), the sugar pill had no effect as an antidepressant,
which is not surprising since it did not contain reboxetine.
8. How might the differences in the enantiomers of reboxetine help explain the different
results for groups A, B, and C?
The synthesized reboxetine is a mixture of the S, S and R, R enantiomers. The plant
probably produces mostly the S, S enantiomer, which has a more potent effect than the R,
R enantiomer. A pill higher in the S, S enanitiomer will have a stronger effect than a
mixture. The yeast probably produces mostly the R, R enantiomer, which has a less
potent effect than the S, S enantiomer. A pill higher in the R, R enantiomer will have a
weaker effect than a mixture.
9. What factors might explain the different responses within each trial group?
Pharmacogenetic differences in the patients most likely accounted for the variation of
effects. Some patients have a body chemistry that does not respond to the drug or rapidly
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Copyright © 2010 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
removes the drug. Others may have a genetic difference that leads to side effects when the
drug is administered. Group D patients who showed a positive response to the sugar pill
exhibited a behavioral response called the placebo effect. Many psychological factors can
cause the placebo effect.
____________________________________________________________________________________
Copyright © 2010 Pearson Education, Inc., publishing as Pearson Benjamin Cummings