In a two-compartment model, what sequence of phases is observed after intravenous administration?

In a two-compartment model, what sequence of phases is observed after intravenous administration?

• A. A rapid distribution phase followed by slower elimination.
• B. A slow distribution phase followed by rapid elimination.
• C. Immediate equilibrium with no distinct phases.
• D. Only elimination occurs with no distribution.

Answer: (A)

In a two-compartment model after an IV dose, the drug quickly moves from the central compartment (blood/plasma) into the peripheral compartment (tissues), causing a rapid distribution that shows up as a sharp drop in plasma concentration. After this fast distribution, the system shifts to an elimination-dominated phase, where drug is removed from the central compartment at a slower rate. This creates the characteristic two-phase, biexponential decline: an initial rapid distribution phase followed by a slower elimination phase. The other patterns don’t fit this behavior—there isn’t an immediate equilibrium with no phases, nor a slow distribution before a rapid elimination, nor elimination occurring without any distribution component.

In a two-compartment model after an IV dose, the drug quickly moves from the central compartment (blood/plasma) into the peripheral compartment (tissues), causing a rapid distribution that shows up as a sharp drop in plasma concentration. After this fast distribution, the system shifts to an elimination-dominated phase, where drug is removed from the central compartment at a slower rate. This creates the characteristic two-phase, biexponential decline: an initial rapid distribution phase followed by a slower elimination phase. The other patterns don’t fit this behavior—there isn’t an immediate equilibrium with no phases, nor a slow distribution before a rapid elimination, nor elimination occurring without any distribution component.