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J Altern Complement Med. 2001 Apr;7(2):141-8.

Can homeopathically prepared mercury cause symptoms in healthy volunteers? A randomized, double-blind placebo-controlled trial.

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  • 1Royal London Homoeopathic Hospital, England, United Kingdom.



To pilot a method for determining whether homeopathically prepared mercury causes more symptoms (a "drug proving") in healthy volunteers than placebo.


One hundred and eighteen (118) healthy volunteers ages 18 to 65 were recruited by local advertising. Subjects unfamiliar with homeopathy undertook a 1-week single-blind placebo run-in, a 1-week of double-blind, randomized treatment on either homeopathically prepared mercury 12C or placebo, and a third week of placebo run-out. Each day, symptoms were recorded on a checklist that included both true mercury symptoms and symptoms not expected to be caused by mercury (false symptoms). Additional symptoms were assessed by open reporting. Outcome was assessed by calculating a score for each day as the number of true symptoms minus the number of false symptoms. The mean score during placebo was then subtracted from the mean score for weeks two and three of the trial.


Fourteen (14) subjects dropped out during placebo run-in. The remaining 104 completed the trial. Baseline comparability was good. Mean difference score was -0.125 (SD 3.47) for mercury and -0.221 (SD 3.01) for placebo (p > 0.2). No significant differences between groups were found for the number of subjects meeting predefined criteria for a drug-proving reaction.


This pilot study failed to find evidence that mercury 12C causes significantly more symptoms in healthy volunteers than placebo. Questionnaires with a limited number of gross symptoms do not seem to be an appropriate methodological technique in drug proving research. If drug-proving phenomena exist, they appear to be rare.

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