# Chapter 5

# Analysis of Urine Data

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## Analysis of Urine Data

### Student Objectives for this Chapter

After completing the material in this chapter each student should:-
- be able to draw the scheme and write the differential equations for a one compartment pharmacokinetic model with elimination of drug and metabolite into urine (parallel pathways of elimination)
- to use the appropriate integrated equations for this pharmacokinetic model to calculate amount of drug excreted into urine
- be able to plot cumulative amount excreted
*versus* time, A.R.E. *versus* time and rate of excretion *versus* time (midpoint) and use these graphs to calculate pharmacokinetic parameters
- be able to define, use, and calculate the parameters:
- ke (excretion rate constant)
- km (metabolism rate constant)
- U
^{∞} and M^{∞}
- fe and fm
- renal and non renal clearance

- be able to use fe, the fraction excreted, to calculate overall elimination rate constants in patients with impaired renal function

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 very young, pediatric patients
- the apparent volume of distribution maybe so large that plasma concentrations are too small to measure
- it may be important to determine the role of metabolism in the elimination of a drug. Analysis of urine data for unchanged drug and metabolite concentrations is essential to the quantitative study of drug metabolism

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.
Quiz

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