The renal excretion rate is equal to:
Assuming that the renal excretion is a
The urine is formed in the kidneys and then collected in the urinary bladder until it is excreted.
The drug excreted in a urine sample reflects the average renal excretion rate over the period of time during which this urine was formed. Urine samples are usually collected over a predetermined time interval.
Renal excretion rate:
1- Select the length of time for each of the urine collection intervals. After drug administration, urine is collected over short intervals initially, then urine can be collected over longer intervals.
To study the renal excretion of drugs with long urine has to be collected over long period of time. Longer collection intervals should be used in this case.
Collection Intervals
1 hr1 hr
2 hrVolume1
Volume2
Volume3
Conc 1
Conc 2
Conc 3
Amount excreted = Volume X Conc
Amount1
Amount2
Amount3
Excretion rate = Amount excreted
Collection interval
2- Determine the volume of each urine collection.
When urine samples are collected, urine has to be collected at the end of the collection interval to make sure that all the drug excreted is included in the collected urine sample.
3- Determine the drug concentration in each urine collection.
4- Calculate the amount of drug excreted during each urine collection interval. (amount = volume x concentration).
5- Calculate the renal excretion rate. (renal excretion rate = amount/ time interval)
6- This is the average renal excretion rate during each urine collection interval.
