DRUG KINETICS-PART-2

CALCULATING HOW THE BODY MOVES THE DRUG

Assessment of how the body moves the drugs through various compartments and to the final destination can be made by the study of some orders and rates of chemical reactions by which the drugs are subjected to move.

Rate of a chemical reaction or process is the velocity with which the reaction or the process proceeds.A change in concentration by time and mathematically can be expressed by the equation

dC/dt where dC is the change in concentration,and dt is the given time interval.

The Order of the reaction or process can be described as the concentration of the drug involved in the process which affect the Rate of the reaction.

1.Zero Order Reactions:-

This is a type of order of the reaction in which the rate of concentration of the reactant changes constantly with respect to time disregarding to the initial concentrations and mathematically dC the change in concentration is matched with dt the change in time as

C=-k0t+C0 (C=the final concentration of the drug,k0 is the zero order rate constant and C0 is the initial concentration.)

This can be expressed by the other way by the following equation,

                     dC/dt = -k0 

k0 can be expressed in unis of concentration per time as mg/ml/hr.

By integrating this we can get the above linear equation that is C=-k0t+C0 where -k0 is he negative slope as the initial concentration goes down as the reaction proceeds.Some drugs are eliminated by he body in this zero order reaction.Their elimination is constant independent of their initial concentration C0.