This situation
is referred to asPseudo-first order kinetics, and is confirmed when First order kinetics are observed for the drug disappearance.
Also applies for reactions
involvingacid
(H3O+)orbase(OH-)when
high concentrations or buffers are used in the reaction solution
thereby maintaining the reagent at constant concentration.
Sometimes, a reaction can be
observed to follow ZERO order kinetics
-d [ D ] / dt=k0
eg,a sparingly soluble
drug undergoes degradation in solution - in
the presence of solid drug, the solution concentration remains constant
at the saturation solubility.