ORIGINAL PAPER Homeopathic pathogenetic trials of Acidum malicum and Acidum ascorbicum P Fisher 1 * and F Dantas 2 1 Royal London Homoeopathic Hospital, UK; and 2 Federal University of Uberla ˆndia, Brazil Two homeopathic pathogenetic trials (HPTs, provings), of identical design were con- ducted: of Acidum malicum 12 cH and Acidum ascorbicum 12 cH. Each trial included 20 healthy volunteers. Both were of double-blind, placebo-controlled, randomised, four period crossover design, with two sequences. ‘Healthy’ was defined in terms of SF-36 scores, medical judgement and blood tests. All volunteers had regular interviews with the same supervisor. No serious adverse reactions occurred. The causal relationship of each symptom with treatment was judged, blind, by the volunteer, the supervisor and a 9-item pathogenetic index. For Acidum malicum 79 symptoms were identified by the supervisor, 57 were included in the final analysis, 22 occurred in verum treatment periods. For Acidum ascorbicum, of 55 symptoms, 39 were included in the analysis. 16 occurred in verum treatment periods. British Homeopathic Journal (2001) 90, 118–125. Keywords: homeopathic pathogenetic trial; proving; Acidum malicum; Acidum ascorbicum; healthy volunteers; pathogenetic index Introduction Homeopathy is based on the idea ‘Let like cure like’ (Similia similibus curentur). In order to understand what symptoms potential homeopathic medicines can provoke in healthy individuals, homoeopaths conduct ‘provings’ or homeopathic pathogenetic trials (HPTs). We consider the latter term preferable, and it will be used in this report, except for historical purposes. 1 HPTs are clinical trials in which healthy volunteers take the substance of interest and their symptoms are recorded. The method was introduced by Samuel Hahnemann in the early nineteenth century. 2,3 Early provings were uncontrolled and used substantial, and sometimes potentially dangerous doses. More recent pathogenetic trials have used various forms of placebo control. In modern provings, the substances have been given in the form of ultra high succussed dilutions (UHSDs) typical of homeopathy, avoiding any risk of toxicity. There are no reports of serious toxicity in compila- tions of modern provings. 4–7 There is a considerable modern literature on proving. 8 – 17 Only a few reports have shown significant differences in symptoms reported by volunteers taking verum and placebo preparations even when the verum preparations were diluted beyond Avogadro’s number. 18,19 The question of whether HPTs using UHSDs yield symptoms which differ from placebo is unresolved. There is currently debate concerning HPT metho- dology: a recent systematic review of HPTs has revealed serious methodological deficiencies in many recent HPTs. 20 The main weaknesses were: inadequate or absent placebo control, low ethical standards, inadequate description of volunteer char- acteristics or definition of ‘healthy’, inadequate description of the medicine used, small sample sizes, lack of clear criteria for judging whether a symptom was likely to have been due to the treatment and lack of statistical analysis. With the exception of sample size, and the consequent limitations on statistical analysis, these methodological weaknesses have been addressed in this study. Other contributions to the debate have focused on the weaknesses of tradi- tional proving methods and the lessons that can be learnt from phase 1 clinical trials 1 and the interaction between subject knowledge and blinding. 21 The HPT reported here examined the effects of Acidum malicum and Acidum ascorbicum 12 cH on healthy volunteers. These are highly diluted prepara- tions of ascorbic acid and malic acid respectively. *Correspondence: P Fisher, Academic Department, Royal London Homoeopathic Hospital, Great Ormond Street, London WC1N 3HR, UK. E-mail: pfisher@gn.apc.org Received 24 July 2000; accepted 2 February 2001 British Homeopathic Journal (2001) 90, 118–125 ß 2001 Nature Publishing Group All rights reserved 0007–0785/01 $15.00 www.nature.com/bhj