For the drugs that follow two-compartment pharmacokinetic model:
After a single oral administration, the drug conc-time profile shows absorption, distribution and elimination phases if the rate constants for these processes are distinctly different from each other.
During constant rate iv infusion the drug conc-time profile approaches biexponentially. It takes 5-6 elimination to reach steady state. Administration of a loading dose results in faster approach to steady state.
During multiple drug administration the drug accumulates in the body until a steady state is achieved. The concentration is proportional to the administered dose and inversely proportional to the .
The drug distribution ratio between the central and the peripheral compartments at steady state during multiple drug administration depends on the ratio of the transfer rate constants k21 and k12.
