Placebo data and weighting

From: Joern Loetsch Subject: Placebo data and weighting Date: Thursday, January 17, 2002 11:15 Dear NONMEM users, I have fitted placebo data from a standard cross-over study and want to incorporat the placebo information intothe PK/PD fit of the verum data. However, the blunt incorporation of the placebo model into the PK/PD fit results in obvious nonsens. The drug effect would be negative in some subjects. The assumption that placebo behaviour would be invarate among study occasions is obviously wrong. When I introduce a weighting factor for the placebo information, the PK/PD fit works fine. However, I'm not sure whether a simple weight factor is adequate. Does anyone have a better solution for the placebo problem? Fitting placebo and active drug data together did not work, the model is probaly too complex, a reliable fit could not be obtained.Thanx in advance. J. Ltsch _______________________________________________________ Jorn Lotsch, MD pharmazentrum frankfurt, Department of Clinical Pharmacology Johann Wolfgang Geothe-University Hospital Theodor-Stern-Kai 7 D-60590 Frankfurt Germany Phone: +49-69-6301-4589 Fax: +49-69-6301-7636