Example: After an iv bolus dose of 250 mg acyclovir the plasma conc-time profile can be described by the following expression:
Cp (mg/L) = 22 e-2.0 t + 6 e -0.23 t
Which of the pharmacokinetic parameters will change if a dose of 500 mg acyclovir is administered ? and what will be the new equation that describes the plasma conc-time profile?
The distribution rate and the
elimination rate do not change
due to the increase in dose
( α and β)
The first-order transfer rate
constants and the first-order
elimination rate constant do not
change due to the increase in dose.
( k12,k21 and k10)
The volume of distribution of the drug is
constant in a particular patient and do
not change due to the change in dose.
(Vc,Vdβ and Vdss)
The AUC will increase proportional to
the increase in dose when the drug
follows linear kinetics.
( AUC)
The total body clearance of the drug
does not change due to the change in
dose when the drug follows linear
kinetics.
Increasing the dose will result in a
proportional increase in the plasma
concentrations. So, the coefficients
A and B will increase due to the
increase in dose.
The only parameters that change due to the change in dose are:
A, B, and AUC
Cp (mg/L) = 44 e-2.0 t + 12 e -0.23 t
