Drug Resistance and Dosing Exercise 8.39 on page 561 explores the topic of
drug dosing and drug resistance by randomizing mice to four different drug
treatment levels: untreated (no drug), light ( \(4 \mathrm{mg} / \mathrm{kg}\)
for 1 day), moderate \((8 \mathrm{mg} / \mathrm{kg}\) for 1 day), or aggressive
( \(8 \mathrm{mg} / \mathrm{kg}\) for 5 or 7 days). Exercise 8.39 found that,
contrary to conventional wisdom, higher doses can actually promote drug
resistance, rather than prevent it. Here, we further tease apart two different
aspects of drug dosing:
duration (how many days the drug is given for) and amount per day. Recall that
four different response variables were measured; two measuring drug resistance
(density of resistant parasites and number of days infectious with resistant
parasites) and two measuring health (body mass and red blood cell density). In
Exercise 8.39 we don't find any significant differences in the health
responses (Weight and \(R B C)\) so we concentrate on the drug resistance
measures (ResistanceDensity and DaysInfectious) in this exercise. The data are
available in DrugResistance and we are not including the untreated group.
(a) Investigate duration by comparing the moderate treatment with the
aggressive treatment (both of which gave the same amount of drug per day, but
for differing number of days). Which of the two resistance response variables
(ResistanceDensity and DaysInfectious) have means significantly different
between these two treatment groups? For significant differences, indicate
which group has the higher mean.
(b) Investigate amount per day by comparing the light treatment with the
moderate treatment (both of which lasted only 1 day, but at differing
amounts). Which of the two resistance response variables have means
significantly different between these two treatment groups? For significant
differences, indicate which group has the higher mean.
(c) Does duration or amount seem to be more influential (at least within the
context of this study)? Why?
