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Loading and Maintenance Doses for a Bolus Infusion Regimen

Description

An intravenous bolus drug regimen often requires a loading dose to rapidly achieve the desired blood levels. There area several ways that this dose can be calculated. At steady state, the rate of drug administration needs to equal the elimination rate.


 

NOTE: The target plasma concentration for drug therapy is usually the average steady state concentration, not the maximum concentration at steady state.

 

loading dose =

= ((target maintenance dose) / (fraction of drug lost from the body per dosage interval))

 

maintenance dose =

= ((loading dose) * (fraction of drug lost from the body per dosage interval))

 

where:

fraction of drug lost from the body during the dosing interval =

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

 

Alternatively:

 

loading dose =

= (volume of distribution) * (target plasma concentration)

 

maintenance dose =

= (average steady state concentration) * (clearance) * (dosing interval)

 

Since k = (0.693 / (half-life)) = ((clearance) / (volume of distribution)), this can be rewritten:

 

maintenance dose =

= C(ave-ss) * (volume of distribution) * 0.693 * (dosing interval) / (half life)

 


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Specialty

ICD-10