This simulation is mainly for visualization purposes. Particles representing drug molecules move randomly about an area depicting a compartment. The area has a hole analogous to drug clearance in the circulation. We consider this a stochastic simulation because it is based on the probability of the random particle path intersecting with the hole. This is a simpler to understand visualization of a first-order system: the more particles there are on the table, the more drop through the hole.
Because of the stochastic nature of the simulation, plots from two consecutive runs with identical user-adjustable settings will be slightly different, as opposed to identical outputs with a similar deterministic simulation. The plots driven by the stochastic simulation display exponential behavior but are rough, especially when the number of particles is small.