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Would
the use of a crossover design be likely to offer advantages
over a parallel group design in comparing a quickly-eliminated
oral drug that blocks pain transmission in patients with
diabetic neuropathy to a placebo?
You
answered:
Yes.
CORRECT
Many published trials show the success of crossover
trials in chronic stable neuropathic pain conditions in which two or three treatments
are each given for 3 – 6 weeks. Pain usually returns to levels approaching baseline
within a week or two after treatment withdrawal. Our clinic’s experience has been
that about 10% of the patients drop out during each 6-week treatment period. Even
considering this, and the greater chance of change in the underlying disease over
the longer treatment period, we have estimated that a crossover study offered
us a level of statistical power that would have required five times the number
of patients enrolled in a parallel group study.
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