; =============================================
DESCRIPTION: complex covariate model
  Example for a more complex covariate model, requiring regression parameters
; =============================================

  [LONGITUDINAL]

  input = {ka,CL,Vc,Q1,Vp1,beta1,beta2,WT0,AGE0}
  WT0 = {use=regressor}
  AGE0 = {use=regressor}

; =============================================
PK:
; =============================================

  ; Model parameters
  ; ----------------
  Tlag1 = 0  ; Absorption lag t (hours)

  ; Model compartments
  ; ------------------
  compartment(cmt=1, amount=Ad)
  compartment(cmt=2, amount=Ac)
  compartment(cmt=3, amount=Ap1)

  ; Model dosing
  ; ------------
  iv(cmt=1, type=1, p=1, Tlag=Tlag1)

  ; Transfer and elimination definitions
  ; ------------------------------------
  transfer(from=1, to=2, kt=ka)
  elimination(cmt=2, k=-(-((CL * (AGE0 - 40)^beta1/WT0^beta2)/Vc + Q1/Vc))-(Q1/Vc))
  transfer(from=3, to=2, kt=Q1/Vp1)
  transfer(from=2, to=3, kt=Q1/Vc)

  ; Output variables
  ; ----------------
  Cc = Ac/Vc

; =============================================
OUTPUT:
; =============================================

  output = {Cc}