Analysis of Urine Data
Objectives:=> To draw the scheme and differential equations for a
one compartment pharmacokinetic model with excretion of drug into urine
=> To recognize and use the integrated equations for this pharmacokinetic
model
=> To construct the plots; cumulative amount excreted versus time, A.R.E.
versus time, and rate of excretion versus time (midpoint)
=> To calculate excretion and metabolism rate constants for parallel
pathway models
=> To use fe, the fraction excreted, to calculate overall elimination rate
constants in patients with impaired renal function
=> To define, use, and calculate the parameter clearance
So far we have looked at most of the information we can get from plasma data
following a rapid intravenous dose of a drug using a one compartment model.
There is another part of the model which can be sampled. Sometimes it is not
possible to collect blood or plasma samples but we may be able to measure the
amount of drug excreted into urine.
- we may not want to take repeated blood samples from certain patient
populations, for example pediatrics
- the apparent volume of distribution maybe so large that plasma
concentrations are too small to measure.
If we collect data for amount of drug excreted into urine it may be possible to
determine the elimination rate constant or half-life and other pharmacokinetic
parameters.
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