Chaotic phenomena

Chaos and illusion

Pharmacology is the study of the interaction of drugs with living organisms, especially humans. The body is a very complicated system, which suggests that the 'effect' induced by a drug is not a single entity but a change in several variables at the same time, all of which are interrelated in a nonlinear fashion. Research on nonlinear systems in other fields of science--commonly known as chaos theory--may therefore be of use in understanding pharmacology, as explained here by J. M. van Rossum and J. E. G. M. de Bie. They argue that in the study of drug effects, several variables should be measured simultaneously. Many pharmacologists prefer to construct an illusion of reality, studying just one of the essential variables and averaging data in a population of subjects, thus losing the opportunity to understand what a drug really does to a patient.

Fascinating rhythm: a primer on chaos theory and its application to cardiology

Nonlinear dynamics is an exciting new way of looking at peculiarities that in the past have been ignored or explained away. We have attempted to give a general introduction to the basics of the mathematics, applications to cardiology, and a brief review of the new tools needed to use the concepts of nonlinear mathematics. The careful mathematical approach to problems in cardiac electrical dynamics and blood flow is opening a window on behaviors and mechanisms previously inaccessible.

Systems dynamics in clinical pharmacokinetics. An introduction

Pharmacokinetics is in essence the study of the input/output relationships of the (human) body, which is considered as a system characterised by a density function of residence times. The input is the dosage rate, and the output is the concentration in the blood. The body transport function is first derived in a model-independent fashion, assuming linear kinetics. It is subsequently defined on the basis of a positive feedback loop of transport through the pulmonary and systemic circulation. Thus, the residence times distribution is based on transit times distributions and recirculation. The relevant dynamic systems parameters are cardiac output, extraction ratio, clearance, volume of distribution, mean transit time and mean residence time. In the case of drug absorption, mean absorption time and bioavailability are also important. In this review, the systems approach in pharmacokinetics is illustrated by clinical and computational experiments.