1) To investigation a first-order process, simulating plasma elimination during and after an iv infusion administration.
BACKGROUND:
By an arrangement of beakers and a constant head water reservoir, it is possible to simulate plasma concentrations and drug amounts in urine after IV. bolus administration. The constant flow of water through the system, causes a first order dilution of the marker, potassium permanganate. You will sample the marker concentrations periodically and analyze the data using the pharmacokinetic methods appropriate to measure the parameters of the system.
METHOD:
Identify the plasma component to the apparatus. Make sure that the water reservoir is full. Turn on the stirrer in the plasma beaker and adjust for gentle mixing. Establish a flow rate of 20 ml/min. Between 15 and 25 ml/min is OK.
You will be collecting plasma samples at 0, 5, 10, 15, 20, 25, 30, 45, and 60 minutes after starting the infusion. Arrange and label test-tubes to accommodate the samples.
One person in the group will act as the injection pump. This person should take 15 drops of the saturated potassium permanganate solution and 'inject' one drops per minute into the plasma compartment until the full dose has been injected. Record this time, T min. The infusion rate is then 250/T mg/min.
Plasma samples. Collect the 5 ml sample at the times designated quickly by pipette. Don't rinse the pipette between samples.
Each sample will be analyzed spectrophotometrically at 540 nm. The absorbance of a 1 mg/ml solution was determined last week. Early samples may need to be diluted to give absorbance readings below 1. Remember to apply this dilution factor in your analysis of the results.
Calibration of the Turner 330 model spectrophotometer
WRITE-UP:
Describe the apparatus, the working differential, and working integrated equation
Data analysis
Plot Cp versus time on semi-log graph paper. Calculate kel from the slope, calculate t1/2. Determine CpT.
Knowing CpT, kel, and k0, calculate the apparent volume of distribution, V.
| Time (min) | Dilution Factor | Absorbance | Concentration |
| 0 | |||
| 5 | |||
| 10 | |||
| 15 | |||
| 20 | |||
| 25 | |||
| 30 | |||
| 45 | |||
| 60 |
Copyright 2001 David W.A. Bourne