RE: Approximate effect compartment

From:"Austin, Daren J" Subject: RE: [NMusers] Approximate effect compartment Date: Fri, 22 Mar 2002 19:41:06 -0000 > Do you mean to use this equation? > Ce(t) = C(t) (KEO/(KEO-alpha_i))*(1-EXP(-(KEO-alpha_i)t) > and substitute alpha_i with ka or kel in the absorption or elimination > phase > of the pk profile? > [Austin, Daren J] Yes > The equation below seems to be missing the A(i) coefficients. > Ce(t) = Sum(i=1..n) (KEO/(KEO-alpha[i])) Exp(-alpha[i].t) > (1-EXP(-(KEO-alpha[i]))t) > [Austin, Daren J] Yes, my solution was missing the A[i]. Essentially my point is that although a multicompartment model fits the dense PK data, I can generate very good PD fits by assuming the one-compartment model solution and estimating an approximte Ce from the observed plasma concentrations. It's really a question of how much the effect compartment needs to follow the central compartment. My approximation is that the dynamics of the effect compartment look one-compartment-like irrespetive of the multi-compartments needed for the plasma PK. When variability in KEO is added I wondered just how valid this approach would be. Thanks for the reference Ken. Daren