title: Pharmacology of ayahuasca administered in two repeated doses.
abstract: BACKGROUND
  Ayahuasca is an Amazonian tea containing the natural psychedelic 5-HT(2A/2C/1A) agonist N,N-dimethyltryptamine (DMT). It is used in ceremonial contexts for its visionary properties. The human pharmacology of ayahuasca has been well characterized following its administration in single doses.
  
  
  OBJECTIVE
  To evaluate the human pharmacology of ayahuasca in repeated doses and assess the potential occurrence of acute tolerance or sensitization.
  
  
  METHODS
  In a double-blind, crossover, placebo-controlled clinical trial, nine experienced psychedelic drug users received PO the two following treatment combinations at least 1 week apart: (a) a lactose placebo and then, 4 h later, an ayahuasca dose; and (b) two ayahuasca doses 4 h apart. All ayahuasca doses were freeze-dried Amazonian-sourced tea encapsulated to a standardized 0.75 mg DMT/kg bodyweight. Subjective, neurophysiological, cardiovascular, autonomic, neuroendocrine, and cell immunity measures were obtained before and at regular time intervals until 12 h after first dose administration.
  
  
  RESULTS
  DMT plasma concentrations, scores in subjective and neurophysiological variables, and serum prolactin and cortisol were significantly higher after two consecutive doses. When effects were standardized by plasma DMT concentrations, no differences were observed for subjective, neurophysiological, autonomic, or immunological effects. However, we observed a trend to reduced systolic blood pressure and heart rate, and a significant decrease for growth hormone (GH) after the second ayahuasca dose.
  
  
  CONCLUSIONS
  Whereas there was no clear-cut tolerance or sensitization in the psychological sphere or most physiological variables, a trend to lower cardiovascular activation was observed, together with significant tolerance to GH secretion.
authors.affiliation: Human Experimental Neuropsychopharmacology, IIB Sant Pau, Sant Antoni María Claret 167, 08025 Barcelona, Spain.
authors.forename: Rafael G
authors.initials: RG
authors.lastname: Dos Santos
authors.forename: Eva
authors.initials: E
authors.lastname: Grasa
authors.forename: Marta
authors.initials: M
authors.lastname: Valle
authors.forename: Maria Rosa
authors.initials: MR
authors.lastname: Ballester
authors.forename: José Carlos
authors.initials: JC
authors.lastname: Bouso
authors.forename: Josep F
authors.initials: JF
authors.lastname: Nomdedéu
authors.forename: Rosa
authors.initials: R
authors.lastname: Homs
authors.forename: Manel J
authors.initials: MJ
authors.lastname: Barbanoj
authors.forename: Jordi
authors.initials: J
authors.lastname: Riba
mesh_terms: D000328:Adult; D031581:Banisteriopsis / Q000737:chemistry*; D001794:Blood Pressure / Q000187:drug effects; D018592:Cross-Over Studies; D004311:Double-Blind Method; D004334:Drug Administration Schedule; D004361:Drug Tolerance; D013006:Growth Hormone / Q000378:metabolism; D006213:Hallucinogens / Q000008:administration & dosage / Q000302:isolation & purification / Q000494:pharmacology*; D006339:Heart Rate / Q000187:drug effects; D006801:Humans; D008297:Male; D004130:N,N-Dimethyltryptamine / Q000008:administration & dosage / Q000302:isolation & purification / Q000494:pharmacology*; D010936:Plant Extracts / Q000008:administration & dosage / Q000494:pharmacology*; D013662:Tea / Q000737:chemistry; D013997:Time Factors; D055815:Young Adult
chemical_list: D006213:Hallucinogens; D010936:Plant Extracts; D013662:Tea; D013006:Growth Hormone; D004130:N,N-Dimethyltryptamine