A simple technique is described which provides plots of simulated tandem first-order processes much like the analog computer. The exponential change in concentration of a solution undergoing dilution at constant volume provides the basis for simulation of first-order processes. A UV-absorbing indicator is introduced into the first of a series of connected containers and the solution is rapidly pumped through the system. The continuously changing indicator concentration in any container can be measured and continuously monitored by a spectrophotometer equipped with a flow cell and recorder. Several pharmacokinetic models, as in delayed-release formulation and in molecular modification, were studied with this device and the resulting plots were found to be accurate and reproducible. The validity of dilution analog simulation of firstorder processes is shown mathematically. One of the uses of the dilution analog simulator is in teaching and visualizing tandem first-order reactions such as pharmacokinetic models.
Keyphrases 0 Analog computer simulation-drug distribution processes 0 Model, three compartment-drug distribution 0 Kinetic equations-drug distribution model 0 Diagrams-models, drug distribution 0 UV spectrophotometry-distribution monitoring