Laplace Transform Examples

One Compartment Models

IV Bolus Dose Administration

Derive the Integrated Equation for the Amount of Metabolite in Urine, X4

The Model

Model with X4 highlighted

Component of Interest - Metabolite in Urine

Step 1. Write the differential equations

Differential equation for X1

Differential equation for X3

Differential equation for X4

Step 2. Transform into the Laplace domain

Equation for X1 in the Laplace domain

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Equation for X3 in the Laplace domain

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Equation for X4 in the Laplace domain

Step 3. Rearrange and solve for L(X3)

Equation for Laplace of X1

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Equation for Laplace of X3

substituting the first term (L(X1)) into the second equation gives

Equation for Laplace of X3

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Equation for Laplace of X4

substituting the second term (L(X3)) into the third equation gives

Equation for Laplace of X4

Step 4. Back transform to produce the integrated equation for X4

Integrated equation for X4

using Laplace tables for the back transform

Integrated equation for X4

using the Fingerprint method for the back transform

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