Medical Hypotheses (2002) 58(6), 523±526 & 2002 Published by Elsevier Science Ltd. doi: 10.1054/mehy.2001.1508, available online at http://www.idealibrary.com on 1 Physical research in dynamized systems C. R. Zacharias UNESP ± State University of Sa Ä o Paulo, Engineering Faculty ± Guaratingueta  , Physics and Chemical Department, Av. Ariberto Pereira da Cunha 333 ± Pedregulho, 12516-410 Guaratingueta Â, SP, Brasil Summary The concept of dynamized medicines is commonly used in homeopathy. As a medical practice, homeopathy is based on clinical observations and experimental assays. In spite of the lack of a credible scientific explanation for its action mechanisms, clinical evidence has been collected since 200 years ago. This paper discusses the most important physical models related to dynamized systems, as well as some perspectives and consequences in studying such systems. While early theories dealt with structural changes in single solvent molecules, modern theories consider collective effects and self-organizing properties. The concept of information was recently introduced to model the capability of a dynamized system to interact with a biological organism, without a molecular agent being needed. The features and limitations of theoretical approaches, as well as experimental results are discussed. & 2002 Published by Elsevier Science Ltd. INTRODUCTION In the early 19th century, a German physician, Samuel Hahnemann (1), was seeking a procedure able to preserve the medicinal properties from a general substance, but reducing its toxicity. He developed a protocol which consisted of a sequence of dilution and shaking, which was named `dynamization' (2), establishing also the clin- ical use of some dynamized substance. His studies, for- malized in principles and laws, were put together (3), originating the therapeutic known as homeopathy. The understanding of the action mechanism of the homeopathic medicines remains unclear, despite clinical evidence of its effectiveness having been collected since 200 years ago. A recent systematic review about clinical trials can be read in Dantas and Fisher (4). This paper reviews theoretical models proposed to explain the physics of a dynamized substance, hereafter referred to as a dynamized system, as well as some con- ceptual and methodological problems related to experi- mental investigations using physical techniques. Its interaction with a biological organism has been described elsewhere (5±13). BASIC CONCEPTS A dynamized system can be produced from any kind of substance of animal, vegetal or mineral nature. Whenever soluble, the substance is diluted in hydroalcoholic solu- tion. Otherwise, three series of trituration with lactose are performed before dilution. One part of this initial solution is transferred to a new recipient with 99 parts of inert solution and shook 100 times. This process (dilution and shaking) can be repeated as many time as desired. Usually, the number of processes performed is used to identify the grade of dynamization, and is named as the potency of the solution. Generally, the final substance chemical con- centration reaches magnitudes lower than 10 À24 Molar, indicating the statistical absence of the original substance. The lack of a molecular substrate, able to retain the 523 Received 6 March 2001 Accepted 16 August 2001 Correspondence to: Carlos Renato Zacharias, UNESP ± DFQ ± Fisica, Av. Ariberto Pereira da Cunha 333 ± Pedregulho, 12516-410 Guaratingueta  , SP, Brasil. Phone: 00 55 12 5252800 int. 207; Fax: 00 55 5252800 int. 209; E-mail: zacha@feg.unesp.br