DRUG KINETICS-PART-10-TWO COMPATMENT MODELS(ORAL)

TWO COMPARTMENT MODELS(ORAL )

In oral administration a drug may not show two comparment models if it absorbed with a rapid distribution and elimination.As the drug is absorbed it is distributed and equibrates with the tissues so that the eliminaion half life of the drug equals to 0.693/b where b is the first order elimination rate constant.

A drug after oral administration shows two compartment models if it is rapidly absorbed and distributed and eliminated slowly.

In general the addition of each new compartment to the model requires an additional first order phase.

The addition of a third new phase indicates the drug has an additional slow distribution and equillibrating into some deep tissue portion.If the drug is given at intervals then it begins to accumulate in the third compartment.

The terminal linear phase in a graph plotted the values of the plasma concentration in the y-axis against time intervals in x-axis represents the elimination phase by the body after equilibration occurs as the last compartment.The rate constant from the elimination phase used to calculate the dosage regimen.

A clear description of multicompartment models is possible only if there are distinct pictures of plasma concentration values from absorption distribution and elimination are available.