The present paper analyzes the work carried out in the Instituto Médico Nacional (IMN), between 1888 and 1915, relating to psychoactive molecules. So far the historiography of the IMN studies on these substances has not been addressed in depth, both in what regards to publications and to the place nervous diseases occupied in the Institute's research agenda.

The objectives of the present work are to identify which psycho-active drugs were studied by the IMN, in what natural species were found (like zapote blanco, madroño borracho or tepozán, for example), as well to define the diseases for which they were targeted (such as insomnia or nervous breakdown) and their treatment.

We also review the legislation on the control of narcotic drugs and psychotropic substances as well as the sanitary laws and the rules contained in the national pharmacopoeia. It was in the first quarter of the 20th century when authorities began to control the use and abuse of the so-called heroic drugs and the popular concept changed from “useful” to “race-degenerating, vice forming” drugs.

Some findings on hypnotic substances yielded by the IMN were published in the Datos para la Materia Medica Mexicana (1898, 1900) and later, in the Farmacología Nacional (1913). Also around this period, negotiations between the IMN and the pharmaceutical House Parke Davis & Son of New York began in order to exploit commercially the active ingredient casimirosa found in zapote blanco. This substance was used successfully in hospitals and in folk medicine due to its sleep restoring properties and lack of side effects. The plant madroño borracho provided a similar hypnotic action as the casimirosa. In the case of the tepozan, its diuretic, hypnotic and analgesic properties were acknowledged, yet at the time the IMN disappeared in 1915, investigations were still in experimental stage.