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Loading Dose

Description

When the time required to reach steady state levels is longer than one wants to wait, a loading dose can be used to achieve comparable levels more rapidly. Loading entails the administration of an amount of drug that will bring the concentration in plasma in the equilibrium phase to the level present during steady state.


 

This can be achieved by administration of:

(1) a single loading dose, if the drug can be tolerated at high plasma concentration during the distribution phase;

(2) several smaller doses, each equivalent to a given fraction of the loading dose, if the drug has a low therapeutic index. This permits better individualization of the loading dose and avoids needless adverse effects that might occur during the distribution of a single large dose.

 

In the case of intermittent drug administration (oral or intermittent infusion), the size of loading dose required to achieve steady state plasma levels can be determined from the fraction of drug eliminated during the dosage interval and from the maintenance dose.

 

loading dose =

= (maintenance dose) / (1 - EXP((-1) * (elimination rate constant) * (dosing interval)))

 


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Specialty

ICD-10