- For every substance, small doses stimulate, moderate doses inhibit, large doses kill.
That is to say, highly diluted pharmaca or poisons enhance life processes, while strong concentrations may inhibit these processes and even terminate them.
The rule was named after Hugo Paul Friedrich Schulz and Rudolf Arndt. The latter originally formulated it in 1888. However, the exceptions to the rule are so numerous that it can not be considered a general law. For instance, many paralysing substances have no exciting effect in weak doses, and what constitutes a weak, medium or strong stimulus is highly individual, as pointed out by Arndt himself.
Scientific basis for homeopathy
This rule has been claimed by some homeopaths as supporting their theories. However, this rule does not apply to the dilutions typically used by homeopaths, which have a high probability of containing no molecules of the diluted substance (note: homoeopathic remedies in its mother tincture or the first solution or first triturate has 10% of original drug substance in 2nd sequential dilute 1% and in 3rd 0.1% in 4th 0.01% and so on; and in homoeopathy not only higher dilutions are used; homoeopaths use all remedies in all dilutions from lowest i.e. 10% of original substance to highest dilution depending on dose required). To explain the purported therapeutic powers of homeopathic remedies (only for ultra high dilutes) Jacques Benveniste created the postulate of "water memory". The water memory hypothesis defies conventional scientific understanding of physicochemical knowledge through which the perceived effect of a chemical compound after its removal from a solution is not expectable due to the assumption no molecules, no effect.
Early studies of how living systems react to stimuli showed that physiological responses could be obtained with some regularity upon exposure to defined doses. Devising a mechanism for these observations proved difficult, and a significant amount of scientific effort was expended on the subject. The work of Arndt and Schultz, along with that of Ernst Heinrich Weber and Gustav Theodor Fechner, was called upon to provide some explanation for observed relationships between dose and response during the early days of pharmacology. However, other concepts such as Hormesis and Receptor Theory eventually supplanted such "laws" as a more complete and well-defined means of describing how chemicals and physiological systems interact.
- Paul Callinan. "Homeopathy: How does it work?". Archived from the original on 2008-01-18. Retrieved 15 August 2009.
- Stumpf, Walter E. (June 2006). "The dose makes the medicine". Drug Discovery Today. 11 (11-12): 550–555. doi:10.1016/j.drudis.2006.04.012.
- Scheindlin, Stanley (May 2001). "A brief history of pharmacology". Modern Drug Discovery. ACS. 4 (5): 87–88.
- Kenakin, Terry (2009). A Pharmacology Primer. Oxford, UK: Elsevier Academic Press. p. 3.
- Holmstedt, B.; Liljestrand, G. (1981). Readings in Pharmacology. New York, USA: Raven Press.