Nonlinear PK Flashcards
1st order PK
-linear
-V, CL, F remain constant w time, dose, concentration
why nonlinear PK?
-when capacity of carriers and enzymes is reached (saturated)
What would happen to Cmax if doubling the dose saturated the ELIMINATION
-remains the same
-elimination rate slower and a lil curved
what are saturable processes
-transport in gut wall
-intestinal metabolism
-plasma protein binding
-active secretion
-saturable metabolism
Saturation during dissolution
-drug conc inc until it cannot and immediately levels out
Saturation during metabolism, transport, plasma protein binding
-curved graph as it reaches max
Linear PK bits
-t1/2, k, CL, V, F consistent
-principles of superposis
Nonlinear PK bits
-concentration DISPROPORTIONAL to dose or become so over time
-dose or time dependent
-t1/2, ke, CL, Vd, F, CLr change
-no principles of superposition
linear rate of elimination
-kel * A
nonlinear rate of elimination
(Vmax * A)/(Km+A)
Km
-NOT an elimination constant
-reflects capacity of system
-equal to drug concentration at 1/2Vmax
-high KM is high capacity
When Cp(dose) is «_space;KM
-first order
-linear
-simplifies to (vmax/km) *CP
When Cp (dose) is»_space; KM
-zero order
-rate=vmax
-IV bags
Phenytoin
-anticonvulsant
-NTI
-CYP2C9 substrate
change in. phenytoin maintenance dose
results in disproportionate changes in ss plasma concentrations
