Bioequivalence and Bioavailability Forum

Hi John!

❝ Equation A: C(t)=A*exp(-alpha*t)+B*exp(-beta*t)+C*exp(-k01*t), where C = -(A+B).

❝ I assumed the equation to be (by remove the last term from equation A):

❝ Equation B: C(t)=A*exp(-alpha*t)+B*exp(-beta*t)?

Since you are using Phoenix/WinNonlin look up in the User’s Guide how hybrid constants (A/α, B/β) are calculated from rate constants (iv bolus: Model 7, ev no lag time: Model 11). See the difference?
You cannot simply drop the C, since A and B are differently calculated in these models. k₀₁ in the ev model is part of A and B – therefore if you simply drop C you cannot use the ev model’s A and B in the iv model. Assuming F=1 calculate A and B for the iv model from D, V, α, β, and k₂₁ according to the formula of Model 7. Then your “Equation B” should work (untested!).