I just found this study summary on PubMed about the drug which is supposedly used by Haitian priests to ‘create’ zombies:
The ethnobiology of the Haitian zombi
Journal of Ethnopharmacology. 1983 Nov;9(1):85-104
For many years students of Haitian society have suggested that there is an ethnopharmacological basis for the notorious zombies, the living dead of peasant folklore. The recent surfacing of three zombies, one of whom may represent the first potentially verifiable case, has focused scientific attention on the reported zombi drug. The formula of the poison was obtained at four widely separated localities in Haiti. The consistent ingredients include one or more species of puffer fish (Diodon hystrix, Diodon holacanthus or Sphoeroides testudineus) which contain tetrodotoxins, potent neurotoxins fully capable of pharmacologically inducing the zombi state. The ingredients, preparation and method of application are presented. The symptomology of tetrodotoxication as described in the biomedical literature is compared with the constellations of symptoms recorded from the zombies in Haiti. The cosmological rationale of zombies within the context of Voodoo theology is described. Preliminary laboratory tests are summarized.
The paper is by ethnobotanist Wade Davis, who also wrote a book on the same topic called The Serpent and the Rainbow.
Davis’ book was the only ethnobiology study that I know of that was also turned into a horror film of the same name – directed by Nightmare on Elm Street director Wes Craven!
Link to PubMed entry for ‘The ethnobiology of the Haitian zombi’.