fast and slow absorption

From 73532.1742@compuserve.com Tue May 9 08:28:58 1995 Subject: fast and slow absorption Hi, This is my response to the original mail by Ralf Brueckner and to the proposals by Jaap Mandema and Alison Boeckmann. I think there is yet another way to model a fast absorption which is followed by a slow absorption: I used ADVAN5 with 2 Depot compartments linked by first-order rate constants to the Central compartment (Compartment 3). It is assumed that DEPOT1 has availability F1 and that DEPOT2 has availability F2=1-F1. Furthermore, both Depot compartments have different lag times (ALAG1 and ALAG2) and different absorption rate constants (K13 and K23). When all these parameters are modelled simultaneously, one can have two types of absorption occur at the same time or one can restrict the difference between ALAG1 and ALAG2. It seems to me that this model offers maximal flexibility to describe any kind of controlled release formulation. Joachim Grevel **** From lewis Tue May 9 10:02:29 1995 This is anopther way of viewing absorption at 2 different rates, but does not correspond to Ralf's model. Ralf's model states that drug comes in first at one rate and then at another. Joachim's models states (when both lag times are equal) that a fraction of total drug enters at one rate, and the remainder at another; simultaneously. Ralf's model gives rise to an absorption rate curve that follows first one exponential and then another; i.e., it is an exponential "spline" with one break-point at the rate-transition time. Joachim's model gives rise to a sum of 2 exponentials. Each modeler will have to decide, based on the physiology of the system he is modeling, which model he prefers.