Nonlinear dynamics and chaos theory: Concepts and applications relevant topharmacodynamics

The theory of nonlinear dynamical systems (chaos theory), which deals with deterministic systems that exhibit a complicated, apparently random-looking behavior, has formed an interdisciplinary area of research and has affecte d almost every field of science in the last 20 years. Life sciences are one of the most applicable areas for the ideas of chaos because of the complex ity of biological systems. It is widely appreciated that chaotic behavior d ominates physiological systems. This is suggested by experimental studies a nd has also been encouraged by very successful modeling. Pharmacodynamics a re very tightly associated with complex physiological processes, and the im plications of this relation demand that the new approach of nonlinear dynam ics should be adopted in greater extent in pharmacodynamic studies. This is necessary not only for the sake of more detailed study, but mainly because nonlinear dynamics suggest a whole new rationale, fundamentally different from the classic approach. In this work the basic principles of dynamical s ystems are presented and applications of nonlinear dynamics in topics relev ant to drug research and especially to pharmacodynamics are reviewed. Speci al attention is focused on three major fields of physiological systems with great importance in pharmacotherapy, namely cardiovascular, central nervou s, and endocrine systems, where tools and concepts from nonlinear dynamics have been applied.