Closed generalized compartmental

Reaction rate parameters required for the distributed pharmacokinetic model generally come from independent experimental data. One source is the analysis of rates of metabolism of cells grown in culture. However, the parameters from this source are potentially subject to considerable artifact, since cofactors and cellular interactions may be absent in vitro that are present in vivo. Published enzyme activities are a second source, but these are even more subject to artifact. A third source is previous compartmental analysis of a tissue dosed uniformly by intravenous infusion. If a compartment in such a study can be closely identified with the organ or tissue later considered in distributed pharmacokinetic analysis, then its compartmental clearance constant can often be used to derive the required metabolic rate constant. 

The equilibrium distribution characterises (but not uniquely) the equilibrium fluctuations. In a closed compartmental system, M - 1 functions of the reaction rate constants can be determined. It may be guessed that not more than M functions of the rate constants can be determined also in the general case. 

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