Analysis of Urine Data

Student Objectives for this Chapter

• 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 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

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Copyright 2001-3 David W. A. Bourne (david@boomer.org)