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Combined Infusion and bolus administration

One reason we give a drug by IV infusion of course is because we need a quick therapeutic response.

One way to achieve a therapeutic concentration more quickly is to give a loading dose by rapid intravenous injection and then start the slower maintenance infusion.

- : For Drugs which can be given as a bolus :-

For example, theophylline again.

To achieve Cpss = 14.1 mg/L; k0 = 60 mg/hr; V = 25 L; kel = 0.17 hr- 1.

A loading dose can be calculated from

(Equation VI-4)


DOSE = V * Cp0 = 25 x 14.1 = 353 mg

Figure VI-3. Linear Plot of Cp versus Time Showing Bolus, Infusion, and Combined Curves

The plasma concentration time curve is as shown in Figure VI-3:-

Using a JAVA aware browser you can create your own version of Figure VI-3.

Plasma Concentration versus Time Plots

Javascript Calculators using Equation VI-2 and VI-4

Calculate Cp given k0, Bolus Dose, kel and V at time t

Enter your own values into each field
k0 (zero order mass/time)
Dose (bolus dose - mass)
kel (first order reciprocal time)
V (volume)
t (time)
Cp from the bolus dose (mass/volume) is:
Cp from the maintenance infusion (mass/volume) is:
The total Cp (mass/volume) is:

An IV bolus and maintenance infusion is one way to achieve a steady state plasma concentration rapidly and maintain it. However, we may not be able to give a bolus dose intravenously...
This page was last modified: 30 August 2001

Copyright 2001 David W.A. Bourne

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