Compartment models formula

For a two-compartment model C=0 and the equation is bi-exponential. The exponents o, jSand y are related to the intercompartmental transfer rate constants by complex formulae. They are related to the half-lives for each of the distribution and terminal phases by the relationship ... 

Since drug elimination mechanisms in humans generally follow first-order kinetics (nonsaturated), an elimination rate constant (Kt) can be determined according to the following formula (assuming a one-compartment model) ... 

For the distributed-parameter skin compartment model, the concentration Csc is calculated by discretizing the stratum corneum compartment into a set of iV -i-2 equidistant nodes and using the central difference formula. This results in the representation of the one-dimensional Fickian diffusion equation to calculate mass flux at any depth within the stratum corneum (46) ... 

Note When scaling a compartment to a very small amount, the presence of SLACKS in the model as species may affect the size resulting from scaling. To compensate for this the following formula for a scale factor has been used. 

Earlier, for this one-compartment oral model, dXe was equated with —dX from Eq. A.47. This resulted in the formula for MRTb, that is the MRT in the body (except for the gastrointestinal tract). Now let us instead focus on elimination of drug from the body as a whole, for which ... 

The EXWAT-model represents an open system with two compartments the fluid and the sediment. As in the fugacity approach of Mackay, equilibria are assumed both for the chemicals dissolved in the fluid and sorbed on the suspended matter and for chemicals dissolved in the pore-water and sorbed on the particulates of the sediment. The volatility was calculated with the formulas developed by Southworth, Liss and Slater (Lyman et al. 1982 Southworth 1979 Liss and Slater 1974). No differentiation was made for the various degradation processes of chemicals in the dissolved or sorbed state, although different degradation behaviour of molecules due to their molecular state can be expected. Similar to Mackay s approach, diffusion, deposition and resuspension is used to describe the exchange processes between sediment and fluid. The main results are called descriptors as seen in SCHEME 2. Several of these are defined in TABLE 2. 

---