The first applications of mescaline in psychiatry: The case of Madame Louise Françoise R. and its contemporary relevance.

At the beginning of the 20th century, while psychiatric knowledge remained limited, some physicians were already exploring innovative experimental paths. This article presents an unpublished clinical case of a patient, Madame Louise Françoise R., treated with mescaline in 1930 by Henri Claude and Henri Ey at Sainte-Anne in Paris, four years before their official publication on the subject. The original notes, explicitly titled "Experiment - Mescaline", document subcutaneous injections of apparently sub-threshold doses (20-40 mg), far below later recognized effective ranges (250-500 mg). Retrospective analysis suggests that the intent was exploratory rather than curative, using mescaline as a functional probe to observe psychopathological mechanisms. The case also illustrates the ambivalence of French psychiatry at the time: a few days after the mescaline trial, the same patient was subjected to malariotherapy, an archetypal shock therapy. This juxtaposition between minimal dosing and radical intervention highlights the oscillation between microdosing and shock paradigms in early psychopharmacology. The phenomenological observations-coloured visions, depersonalisation, and the formula "mescaline releases but does not create fantasies"-anticipate contemporary models of psychedelic action. Yet the clinical improvement followed febrile therapy rather than mescaline. For contemporary researchers, this case provides historical perspective on microdosing, reminding us that early psychedelic trials were often diagnostic, exploratory, and ethically fragile. It resonates with today's renewed interest in microdosing, while underlining the need for rigor, consent, and ethical safeguards in modern psychedelic research.