Re: Placebo in indirect PD models

From: Mark Sale - Next Level Solutions mark@nextlevelsolns.com Subject: Re: [NMusers] Placebo in indirect PD models Date: 26-Apr-2006 21:33 Ivan, General thoughts: Placebo effect is (IMHO) not generally part of the pharmacology. This, it occurs to me is the case in pain. It is something else, expectations (on the part of the patient or the observer), other behavioral/dietary/lifestyle changes etc. So, (also IMHO) it wouldn't be my first choice to model it is part of the drug-related biology. Rather, it is something separate. My favorite placebo model is something that I just simply add to the response plac = Pmax*Time/(TC50+TIME) Y = (F+plac)*exp(eps(1)) where Pmax is the maximum possible placebo effect, and TC50 is the time at which half the maximum is acheived. I really can't think of a case where I would consider the placebo effect to be part of the pharmacology. If you would like something to go up and then down (as, I beleive occurs in pain placebo models), you might consider just a one-compartment, first order absorption model. Mark Sale MD Next Level Solutions, LLC www.NextLevelSolns.com