I'm quite certain that you have this essentially backwards. As...

I'm quite certain that you have this essentially backwards. As far as I understand, it will be necessary to demonstrate actual pain reduction in humans with the topical oxycodone patch, and from sad experience I can tell you that this can be more problematic than one might expect. The placebo effect is always a problem, and the larger number of trial participants and the time required to washout the placebo effect will always make these trials more difficult, larger, more time consuming, and expensive than a trial that essentially measures serum drug concentrations.