Fractal space and time — Sources of nonlinearity in drug elimination

This paper is concerned with a ne w idea in the area of pharmacokinetics, namely the concept of fractality in both spatial and temporal domains. Physiological fractality is due to both the architecture of organs of drug elimination such as the vasculature of the liver and the time-depende nt processess that exhibit self-similarity. Both diffusion on branched and porous media and chemical kinetics in such media result in new types of invasion and elimination characteristics. We illustrate the general features of pharmacokinetic fractality with two vastly different examples of data sets: one obtained for the heart medication called mibefradil and the other for the chemotherapeutic agent paclitaxel. While the sources of fractality in these two cases are quite different, one is due to spatial distribution and the other is due to protein binding, the results in both cases show power law time dependence which is a hallmark of fractality.