RE: Two formulation of the same Drug

From: "Bachman, William" Subject: RE: [NMusers] Two formulation of the same Drug Date: Tue, 30 Apr 2002 10:27:41 -0400 A couple of things off the top of my head: 1. CL (CL/F as you are modeling it) confounds the CL (which is probably the same for both formulations) and the F (which is different), so you might try separating out the F by modeling F1. (and applying the formulation covariate to that parameter instead of CL). The confounding might explain why you can model them separately but not together. 2. THETA(5) is constrained (5,20,100). Make sure it's really in that range. I try not to over-constrain parameter if I don't have to. I just generally constrain to be positive (if appropriate.) might explain the at boundary situation. 3. Does either formulation exhibit a lag? if so, model it. 4. Is there significant variability in KA? if so, model it. Fixing the one KA may also be over-constraint. Not knowing your data, its' hard to tell. good luck, Bill *******