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Does
this result Drug K as an effective analgesic?
You answered:
Yes. This
result demonstrates that Drug K is an effective analgesic.
INCORRECT
Although
one explanation of the results is that Drug K is an effective
analgesic, allowing patients to decrease their use of supplementary
morphine, there are other possibilities, particularly in
view of the lack of any reduction in pain intensity. (It
is possible that patients in the placebo group took enough
extra morphine to reduce their pain to the level of the
Drug K group, but patients rarely self-administer analgesics
liberally enough to overcome such treatment differences.)
Alternative
explanations may include:
- Drug
K made patients too sleepy to push the PCA button;
- Drug
K potentiates opioid-induced nausea and patients became
so nauseated that they were afraid of taking morphine;
and
- Drug
K made patients anxious and those who were fearful of
opioids to begin with were even more reluctant to push
the PCA button.
Another
way of expressing this is to say that pain and pain relief
are defined by the patient’s report, while the self-administration
of analgesic is a behavior. Measurements of behavior often
correlate to a modest extent with pain report. They may
also add to the understanding of the impact of pain. And,
in certain circumstances, e.g. in very young children and
demented or unresponsive patients, they may need to substitute
for pain report (Weiner
et al., 1999). However, in most circumstances, neither
behaviors nor laboratory measurements can replace the subject’s
pain report.
Now
consider a second question about the same research case
problem.
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