Subjective effects and tolerability of the South American psychoactive beverage Ayahuasca in healthy volunteers

8/14/2019 Subjective effects and tolerability of the South American psychoactive beverage Ayahuasca in healthy volunteers

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Abstract Rationale: Ayahuasca is a South Americanpsychoactive beverage that contains the naturally occur-ring psychedelic agent N,N-dimethyltryptamine (DMT).

This tea has been used for centuries in religious andmedicinal contexts in the rain forest areas of SouthAmerica and is presently gaining the attention of psyche-delic users in North America and Europe. Objectives: Inthe present study, the psychological effects and tolerabil-ity ofayahuasca were assessed.Methods: Three increas-ing doses of encapsulated freeze-dried ayahuasca (0.5,0.75, and 1.0 mg DMT/kg body weight) were adminis-tered to six healthy male volunteers with prior experi-ence in the use of this tea, in a single-blind crossoverplacebo-controlled clinical trial.Results: Ayahuasca pro-duced significant dose-dependent increases in five of thesix subscales of the Hallucinogen Rating Scale, in theLSD, MBG, and A scales of the Addiction ResearchCenter Inventory, and in the liking, good effects andhigh visual analogue scales. Psychological effectswere first noted after 3060 min, peaked between60120 min, and were resolved by 240 min. The tea waswell tolerated from a cardiovascular point of view, with atrend toward increase for systolic blood pressure. Modi-fied physical sensations and nausea were the most fre-

quently reported somatic-dysphoric effects. The overallexperience was regarded as pleasant and satisfactory byfive of the six volunteers, while one volunteer experi-

enced an intensely dysphoric reaction with transient dis-orientation and anxiety at the medium dose and volun-tarily withdrew from the study. Conclusions: Ayahuascacan be described as inducing changes in the perceptual,affective, cognitive, and somatic spheres, with a combi-nation of stimulatory and visual psychoactive effects oflonger duration and milder intensity than those previous-ly reported for intravenously administered DMT.

Keywords Ayahuasca DMT Subjective effect Tolerability Human

Introduction

Ayahuasca, a potent psychotropic drink that has beenused for centuries for magico-religious purposes and folkmedicine in the Amazon and Orinoco river basins(Dobkin de Ros 1972; Schultes and Hofmann 1982), isbecoming increasingly popular in Europe and NorthAmerica as a sacramental drug (Metzner 1999). In recentyears, the use of ayahuasca has spread outside SouthAmerica, and several groups using this tea have becomeestablished in Spain and other European countries(Marshall 1997; Lpez 1999), where the tea is reportedlyused to facilitate self-knowledge and introspection. Arelevant facet in expanding ayahuasca use can be attrib-uted to the growing interest of the many individuals whoare interested in shamanic practices, in addition to theactivities of a number of Brazilian syncretic religions,particularly the Santo Daime and the Unio do Vegetal,that have combined Old World religious beliefs with theindigenous use of ayahuasca. Because this tea containsmeasurable amounts ofN,N-dimethyltryptamine (DMT),the ayahuasca churches are actively working to obtainlegal exemption for ayahuasca use within a religiouscontext outside Brazil, the only country where it current-ly enjoys legal protection, analogous to the status held

J. Riba G. Urbano A. Morte R. Antonijoan M.J. Barbanoj ()rea d'Investigaci Farmacolgica, Institut de Recerca,Hospital de la Santa Creu i Sant Pau (HSCSP),St. Antoni Maria Claret, 167, 08025 Barcelona, Spaine-mail: [email protected].: +34-93-2919019, Fax: +34-93-2919286

J. Riba G. Urbano A. Morte R. Antonijoan M.J. BarbanojDepartament de Farmacologia i Teraputica,Universitat Autnoma de Barcelona, Barcelona, Spain

A. Rodrguez-FornellsMedizinische Hochschule Hannover, Hannover, Germany

M. MonteroServei de Psiquiatria, Hospital de la Santa Creu i Sant Pau (HSCSP),Barcelona, Spain

J.C. CallawayDepartment of Pharmaceutical Chemistry, University of Kuopio,Kuopio, Finland

Psychopharmacology (2001) 154:8595DOI 10.1007/s002130000606

O R I G I N A L I N V E S T I G AT I O N

Jordi Riba Antoni Rodrguez-FornellsGloria Urbano Adelaida Morte Rosa AntonijoanMaria Montero James C. CallawayManel J. Barbanoj

Subjective effects and tolerability of the South American psychoactive

beverage Ayahuascain healthy volunteersReceived: 4 July 2000 / Accepted: 3 October 2000 / Published online: 14 December 2000 Springer-Verlag 2000


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by the Native American Church for the use of peyote( Lophophora williamsii, a mescaline-containing cactus)in the United States. Even though the number of users isstill relatively small outside of Brazil, ayahuasca use hasraised concerns for public health (Callaway and Grob1998), and extensive clinical data on its somatic, psycho-logical, and neurophysiological effects are indicated.

Ayahuasca, also known as Daime or Hoasca in Bra-

zil, Yaj in Colombia, or Natem in Ecuador, is generallyobtained by infusing the shredded stalk of the malpighi-aceous vine Banisteriopsis caapi with the leaves ofPsy-chotria viridis (Rubiaceae) or Diplopterys cabrerana(Malpighiaceae). B. caapi contributes a mixture of-car-boline alkaloids to the tea, particularly harmine, tetra-hydroharmine (THH), and trace amounts of harmaline(Rivier and Lindgren 1972). P. viridis and D. cabreranaare rich in the psychedelic indole DMT (River andLindgren 1972; Schultes and Hofmann 1980; Callawayet al. 1996).

DMT, the main psychotropic agent of ayahuasca, iscapable of eliciting an intensely emotional dream-like

experience characterized by vivid visual imagery, per-ceptual and cognitive changes, and profound modifica-tions in the sense of self and reality, when administeredparenterally (Strassman et al. 1994). On the molecularlevel, DMT has affinity for 5-HT2 and 5-HT1A bindingsites, similarly to LSD (Pierce and Peroutka 1989;Deliganis et al. 1991), and is structurally similar to sero-tonin. Interestingly, DMT is known for its lack of psy-choactivity when orally ingested, even in quantities inthe order of grams (Ott 1999), due to metabolism bymonoamine oxidase (MAO; Suzuki et al. 1981). The -carbolines present in ayahuasca, particularly harmineand harmaline, have been found to inhibit MAO

(McKenna et al. 1984), an effect that apparently allowsthe viable access of DMT to the systemic circulation andthe central nervous system. In addition to the action ofDMT on serotonin receptors, it has also been suggestedthat ayahuasca's psychoactive effects may also be partlydue to a general increase of catecholamines and seroto-nin (Callaway et al. 1999). This increase would be due toboth the inhibited metabolic breakdown of serotonin inaddition to its uptake inhibition by THH and also compe-tition with DMT for receptor sites (Callaway et al.1999). Thus, ayahuasca constitutes a very complex psy-choactive preparation, acting at least through three dif-ferent pharmacologic mechanisms.

In the present paper we report a single-blind placebo-controlled clinical trial conducted with ayahuasca, inwhich the subjective effects and tolerability of three dif-ferent doses ofayahuasca were evaluated in healthy vol-unteers. This study is part of a wider research project de-signed to further characterize the pharmacologic effectsof this tea.

Materials and methods

Volunteers

For ethical reasons, participation in this initial study was limitedto six healthy male volunteers having previous experience withayahuasca. Volunteers were contacted by word of mouth in theBarcelona area of Spain, and all had previous exposure to thetea, but had no formal connections to any ayahuasca church.The volunteers were given a structured psychiatric interview(DSM-III-R) and completed the trait-anxiety scale from the state-trait anxiety inventory (Spielberger et al. 1970). Exclusion criteriaincluded a present or past history of axis-I disorders and alcohol orother substance dependence, and high scores on trait anxiety. Fol-lowing the psychiatric interview, participants underwent a com-plete physical examination that included a medical history, labora-tory tests, ECG, and urinalysis. Mean age was 32.2 years (range:2644), mean weight 71.5 kg (range: 6685), and mean height174.3 cm (range 167186). All volunteers had previous experiencewith cannabis, cocaine, psychedelics, and other illicit substances.Regarding their prior experience specifically with ayahuasca, vol-unteers 1 and 2 had previously consumed it on 10 occasions, vol-unteer 3 on about 60 occasions, volunteer 4 on 2 occasions, volun-teer 5 on 6 occasions, and volunteer 6 on 30 occasions. The studywas conducted in accordance with the Declarations of Helsinkiand Tokyo concerning experimentation on humans, and was ap-proved by the hospital's ethics committee and the Spanish Minis-try of Health. The volunteers received detailed information on thenature ofayahuasca, the general psychological effects of psyche-delics, and their possible adverse effects, as reported in the psychi-atric literature. All volunteers gave their written informed consentto participate.

Drug

A 9.6 litre batch of ayahuasca (Daime) was obtained from CE-FLURIS, a Brazilian-based religious organization related to theSanto Daime church. The tea had the appearance of a brown-red-dish suspension with a characteristic bitter-sour taste and smell,and a markedly acidic pH (3.63). In order to mask the drug in thesingle-blind design and establish accurate dosings, the tea under-

went a freeze-drying process that yielded 611 g of a yellowishpowder, which was subsequently homogenized and analyzed for al-kaloid contents by an HPLC method previously described in the lit-erature (Callaway et al. 1996). One gram of freeze-dried materialcontained 8.33 mg DMT, 14.13 mg harmine, 0.96 mg harmaline,and 11.36 mg THH. Thus, the alkaloid concentrations in the origi-nal tea were as follows: DMT 0.53 mg/ml, harmine 0.90 mg/ml,harmaline 0.06 mg/ml, and THH 0.72 mg/ml. The DMT concentra-tion found in the tea was similar to that reported previously for asample of Daime (Liwszyc et al. 1992) and several Peruvian ay-ahuasca samples (McKenna et al. 1984), and twice as great as theamount reported for a sample ofHoasca from the Brazilian churchUnio do Vegetal (Callaway et al. 1996). Similarly, the -carbolineconcentrations found in the ayahuasca used in the present studywere also higher than those reported in the previously mentionedsamples. In view of the mild psychological effects reported from

the 0.48 mg DMT/kg body weight dosage (Grob et al. 1996), andconsidering the total amounts of DMT consumed in what havebeen reported as typical doses (McKenna et al. 1984; Liwszyc et al.1992), the following experimental doses were chosen for the pres-ent study: 0.5 mg DMT/kg body weight as the low dose and 0.75and 1.0 mg DMT/kg body weight as the medium and high dose, re-spectively. The freeze-dried material was encapsulated in 00 gela-tin capsules containing 0.5, 0.25, or 0.125 g, and stored at 20Cunder nitrogen atmosphere and protected from light until adminis-tered to the volunteers. Placebo capsules consisted of 00 gelatincapsules with 0.75 g lactose. Each volunteer received his calculatedindividual dose by combination of these capsules. Placebo capsuleswere added when necessary, so that all volunteers received 20 cap-sules on each experimental day.

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Study design and experimental procedure

The study was carried out in a single-blind fashion. Volunteerswere informed that they would receive a single oral dose of encap-sulated freeze-dried ayahuasca (one low, one medium, and onehigh dose) or placebo on each of 4 experimental days. In order toavoid subjective effects related to expectancy, the volunteers werealso informed that administrations would be made in a double-blind balanced fashion. For security reasons, they were actuallyadministered in increasing doses, i.e., placebo for the first session,

the low dose containing 0.5 mg DMT/kg for the second session,the medium dose containing 0.75 mg DMT/kg for the third ses-sion, and the high dose containing 1.0 mg DMT/kg for the fourthand final session, in order to control for tolerability and the possi-ble risk in elevations of cardiovascular parameters. Two weeksprior to the beginning of the experimental sessions, volunteers ab-stained from any medication or illicit drug and remained drug-freethroughout the 4 study weeks. Urinalysis for illicit drug use wascarried out for each experimental session. Additionally, volunteersabstained from alcohol, tobacco, and caffeinated drinks 24 h priorto each experimental day. Experimental days were a week apart.

The volunteers were admitted to the research unit on 4 separateexperimental days. Upon arrival at 8:00 a.m. under fasting condi-tions, a urine sample was collected, a cannula was inserted in thecubital vein of their right arm for drawing blood samples, and cap-sules were administered by approximately 9:00 a.m. with 250 ml

tap water. Throughout the experimental session the volunteers re-mained seated in a comfortable reclining chair in a quiet and dim-ly lit room. The experimenter remained beside the volunteer formost of the time, and no music was used during the sessions. Fourhours after administration of the capsules, the volunteers left theroom, answered subjective effect questionnaires, were able to havea light meal if they wished to, and were discharged after 5 h fromthe administration.

Measurements

Besides the measures described below, spontaneous verbally re-ported effects were also recorded. Additionally, blood sampleswere drawn at set time points in order to establish the alkaloidspharmacokinetic profiles (not reported here). The time points se-

lected for the measurements described below were based on fieldobservations of duration of ayahuasca effects, and on the pub-lished pharmacokinetic and pharmacodynamic data by Callawayet al. (1999).

Psychological measures

The psychological effects elicited by ayahuasca were measured bymeans of visual analogue scales (VAS) and self-report question-naires. VAS were 100-mm horizontal lines with the following la-bels: any effect indicated any effect, either physical or psycho-logical, that the volunteer attributed to the administered dosage;good effects indicated any effect the volunteer valued as good;liking reflecting that the volunteer liked the effects of the ad-ministered substance; drunken indicating any dizziness or light-

headedness; stimulated indicating any increases in thoughtspeed and/or content, or any increases in associations and/or in-sights; and high which reflected any positive psychological ef-fect the volunteer attributed to the treatment. The volunteers wererequested to answer the VAS immediately before administrationand at 15, 30, 45, 60, 90, 120, 150, 180, 210, and 240 min afteradministration.

Self-report questionnaires included Spanish adaptations of theHallucinogen Rating Scale (HRS) and the Addiction ResearchCenter Inventory (ARCI). The HRS version, which had been pre-viously translated from English and validated in Spanish (Riba etal. 2000), includes six subscales: somaesthesia, reflecting so-matic effects; affect, sensitive to emotional and affective re-sponses; volition, indicating the volunteer's capacity to willfully

interact with his/her self and/or the environment; cognition,describing modifications in thought processes or content; percep-tion, measuring visual, auditory, gustatory, and olfactory experi-ences; and finally intensity, which reflects the strength of theoverall experience (Strassman et al. 1994). The ARCI (Lamas etal. 1994) consists of five scales or groups: morphine-benzedrinegroup (MBG), measuring euphoria; pentobarbital-chlorpromazine-alcohol group (PCAG), measuring sedation; lysergic acid diethyl-amide scale (LSD), measuring somatic-dysphoric effects; and thebenzedrine group (BG) and the A scale, for amphetamine, both

sensitive to stimulants. The volunteers answered the ARCI imme-diately before drug administration and, 4 h after drug intake, theyagain answered the ARCI and the HRS.

Tolerability measures

Cardiovascular variables were recorded by means of a sphygmo-manometer cuff (Dinamap Critikon, Tampa, Fla., USA) which wasplaced around the volunteer's left arm. Blood pressure [systolic(SBP) and diastolic (DBP)] and heart rate were measured immedi-ately before administration (baseline) and at 15, 30, 45, 60, 90,120, 150, 180, 210, and 240 min after intake. Somatic-dysphoriceffects were recorded by means of the questionnaires previouslymentioned, and as spontaneous verbal reports. Finally, after eachexperimental session, a blood sample was taken for laboratory

testing, which included blood cell counts, plasma bilirubin, creati-nine, and liver enzymes.

Statistical analysis

Values from cardiovascular measures and ARCI scores were trans-formed to differences from baseline and differences from pread-ministration scores, respectively. Transformed values, HRS scores,and mean values obtained across time points for a given treatment(i.e., cardiovascular and VAS data) were analyzed by means of anon-parametric Friedman test. When a significant effect was ob-served, post hoc comparisons were performed using the Wilcoxontest. In all tests performed, differences were considered statistical-ly significant for P values lower than 0.05.

Results

Psychological effects

Results for the statistical analyses performed on all sub-jective effect variables are presented in Table 1. A signif-icant effect of treatment was observed for all seven VASitems, all HRS subscales except volition, and the A,MBG, and LSD scales of the ARCI. The 0.5 mgDMT/kg body weight dosage chosen in the present studyas the lower dose proved to be psychoactive in five ofthe six volunteers and subthreshold for the sixth volun-teer, who mistook it for the placebo. At this dose, theWilcoxon test showed significant effects for all VASitems except for high. A significant effect was alsofound for the HRS somaesthesia subscale. Finally, theARCI questionnaire showed a significant increase in theMBG scale.

When administered at 0.75 and 1.0 mg DMT/kg bodyweight, ayahuasca was correctly identified as an activesubstance by all participants. All VAS items and all HRSsubscales, except for volition, discriminated betweeneach of these two doses and the placebo. At the medium

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dose (i.e., 0.75 mg DMT/kg) the ARCI MBG and Ascales showed statistically significant differences fromthe placebo. At the high dose, the LSD, MGB, and Ascales showed significant differences from the placebo.Regarding discrimination between the doses, five of theseven VAS items and the HRS cognition subscale wereable to discriminate between the low and the high doses.

None of the variables were able to discriminate betweenthe medium and the high doses. Three VAS items, anyeffects, drunken, and high, were discriminative be-tween the low and medium doses. Discrimination be-tween these two doses was also achieved by the HRSsomaesthesia, affect, and intensity subscales.

Scores on the HRS subscales for the four experimen-tal conditions are shown in Fig. 1. Pre- and post-treat-ment scores on the ARCI scales for the four experimen-tal conditions are shown in Fig. 2. The time course of ef-fects, as reflected by the seven VAS items, is presentedin Fig. 3. The initial somatic effects ofayahuasca ap-peared between 1530 min, which translated as increasesin the any effect VAS. This was followed by an onsetof psychological effects at around 3060 min, which wasreflected by the increases in the other six VAS items.Both somatic and psychic effects peaked between 60 and120 min after drug intake and gradually decreased tobaseline levels at approximately 240 min. It is worth not-ing that the good effects and liking items of the VASremained elevated at 240 min after drug administration,when most of the perceptual, cognitive, and affective ef-fects had disappeared. The volunteers verbally describedthis state as a lingering sensation of well-being after theresolution of the more intense psychotropic effects.

Tolerability

Cardiovascular effects

Mean values for SBP, DBP, and heart rate over time arepresented in Fig. 4 as differences from their baseline val-ues. All three ayahuasca doses produced increases in

SBP and DBP when compared with placebo. Changeswere not statistically significant, although a robust trendtoward significance was observed for SBP (P=0.0503) atthe high dose. The peak differences in SBP were13.8 mm Hg between the high dose and placebo,13.4 mm Hg between the medium dose and placebo, and8.8 mm Hg between the low dose and placebo. The max-imal increases in SBP were observed at 90 min after ad-ministration of all three ayahuasca doses. The peak dif-ferences in DBP were 10.4 mm Hg between the highdose and placebo, 9.8 mm Hg between the medium doseand placebo, and 8.6 mm Hg between the low dose andplacebo. The maximal increases in DBP were observedat 60 min after administration of all three ayahuascadoses. Mean arterial pressures showed a 10.6 mm Hgmaximum difference from placebo at 60 min. Heart ratewas affected very little by ayahuasca. Increases abovebaseline values were only seen for the medium and highdoses, with peak differences of 9.2 beats/min betweenthe high dose and placebo, 8 beats/min between the me-dium dose and placebo, and 6.4 beats/min between thelow dose and placebo at 45 min after drug administra-tion. At no point did SBP reach 140 mm Hg, nor didheart rate reach 100 beats/min for any individual volun-teer. On the other hand, two volunteers showed sporadic

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Table 1 Statistical analysesperformed on the visual ana-logue scale (VAS) scores (meanvalues across ten time points)and on scores obtained for theHallucinogen Rating Scale(HRS) subscales and AddictionResearch Center Inventory(ARCI) (differences from pre-drug values) (n=5).NS Not sig-

nificant, A amphetamine scale,LSD lysergic acid diethylamidescale,BG benzedrine group,MBG morphine-benzedrinegroup, PCAG pentobarbital-chlorpromazine-alcohol group

Variable Friedman test Wilcoxon test

Placebo 0.5 mg/kg 0.75 mg/kg

P value 0.5 0.75 1.0 0.75 1.0 1.0

VASAny effect ** * * * * * NSGood effects ** * * * (*) * NS

Visions * * * * NS (*) NSLiking ** * * * (*) * NSDrunken ** * * * * * NSStimulated ** * * * (*) NS NSHigh ** (*) * * * * NS

HRSSomaesthesia ** * * * * NS NSPerception * NS * * NS (*) NSCognition * NS * * (*) * NSVolition NS Affect ** (*) * * * (*) NSIntensity ** (*) * * * NS NS

ARCIMBG ** * * * (*) NS NS

BG NS A ** (*) * * NS (*) NSLSD * (*) (*) * NS NS NSPCAG NS

*P


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DBP values between 9193 mm Hg after the mediumand high doses, which lasted between 15 and 30 min.

Somatic-dysphoric effects

Table 2 lists the main somatic-dysphoric effects reportedby the volunteers either spontaneously, or as positive re-sponses to particular items in the HRS and ARCI ques-tionnaires.

Blood analysis

No clinically relevant alterations were observed in thehematological or biochemical parameters tested aftercompletion of each experimental session.

Verbal reports

The first effects noted by the volunteers were somaticmodifications which included burning sensations in thestomach, tingling sensations, changes in perception ofbody temperature and skin sensitivity, and mild nausea.The onset of psychic effects was generally sudden andintense. Volunteers reported a certain degree of anxietyor fear at this initial stage, tending to decrease thereaf-ter. Visual imagery was characteristic and dose-depen-dent. The images and visual modifications did not per-sist throughout the entire experience, but usually cameand went in waves. These effects ranged from increases

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Fig. 1 Mean scores on the six Hallucinogen Rating Scale (HRS)subscales after administration of placebo (s), 0.5 mg N,N-dimeth-yltryptamine (DMT)/kg body weight ayahuasca (lightly shaded),0.75 mg/kg (shaded), and 1.0 mg/kg (s). Error bars denote 1standard error of mean (n=5). Significant differences from placebo(Wilcoxon test, P


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in an objects brightness and sharpness, or as vibrationsin the visual field, to rapidly moving patterns, andscenes that were visible with eyes either closed or openat the medium and high doses. Changes in auditory per-ception were also reported and showed a dose-depen-dent effect. Hearing was perceived to be enhanced, withsounds becoming more clear and distinct. Although in-frequent, transient auditory phenomena were reported insome subjects at the three doses. Thought processeswere also modified, with the volunteers reporting an en-hanced rate of thinking which generally centered on per-sonal psychologic content. These thoughts were experi-enced as providing new insight into personal concerns.As the doses increased, emotional reactions were inten-sified, with the volunteers experiencing happiness, sad-ness, awe, amazement, and at times simultaneously con-

tradictory feelings. At the medium and high doses, vol-unteers agreed on the similarity of the experience todreaming. Memories were present, mostly related to re-cent personal matters. The sense of self and the passingof time were deeply affected at the medium and highdoses. While sensations of closeness to others, happi-ness, and euphoria were similar at the medium and highdoses, sensations of detachment from the body, onenesswith the universe, and chaos, were more frequently re-ported with the latter. Five of the six volunteers wereable to interact with the experimenter and the environ-ment without major problems at all three doses. Thesixth volunteer experienced a brief but intense disorien-tation state at the medium dosage. It is noteworthy thatthis volunteer had the least amount of experience withayahuasca, having consumed it prior to the study on on-

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Fig. 2 Mean pre- (s) and postdrug (lightly shaded) administrationscores on the five Addiction Research Center Inventory (ARCI)scales, after each of the four experimental conditions. Error barsdenote 1 standard error of mean (n=5). Significant differencesfrom placebo (Wilcoxon test, P


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Fig. 3 Time curves of scores on the seven visual analogue scale(VAS) items (means) after administration of placebo (q), 0.5 mgDMT/kg body weight ayahuasca (s), 0.75 mg/kg (v), and1.0 mg/kg (x). Error bars denote 1 standard error of mean (n=5)


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ly two occasions. Verbal support was sufficient to gethim through this temporary crisis, but he was left with ageneral feeling of dissatisfaction toward the experienceand withdrew from the study. Nevertheless, all volun-teers, including this one, were well aware of the effectsbeing caused by the administered drug and of their tran-sient nature.

Discussion

The administration ofayahuasca to experienced healthyvolunteers induced intense modifications of their con-scious state, which was evaluated as dose-dependent ele-vations in all VAS items used, in five of the HRS sub-scales, and in the MBG, LSD, and A scales of the ARCIquestionnaire. At no time of the study did any of the vol-

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Fig. 4 Time course of cardiovascular measures (means) as differ-ences from baseline after administration of placebo (q), 0.5 mgDMT/kg body weight ayahuasca (s), 0.75 mg/kg (v), and1.0 mg/kg (x). Error bars denote 1 standard error of mean (n=5)

Table 2 Somatic-dysphoric ef-fects spontaneously reported bythe six volunteers, or as posi-tive responses on particularitems of the HRS and ARCIquestionnaires on the 4 experi-mental days, presented as mostto least frequently reported.Figures indicate the number ofsubjects who reported a specif-ic effect, regardless of intensity,at the three different ayahuascadoses administered and placebo

Somatic-dysphoric effect Placebo 0.5 mg/kg 0.75 mg/kg 1.0 mg/kg

1 Body feels differenta 1/6 5/6 6/6 5/52 Nauseaa 0/6 4/6 5/6 3/53 Change in body temperaturea 1/6 4/6 4/6 3/54 Electric/tingling feelinga 1/6 2/6 3/6 5/55 I have a disturbance in my stomachb 0/6 3/6 4/6 2/56 My hands feel clumsyb 1/6 2/6 3/6 3/57 My speech is slurredb 0/6 3/6 3/6 2/58 Urge to urinatea 1/6 1/6 3/6 3/59 Feel body shake/tremblea 0/6 1/6 3/6 2/5

10 Urge to move bowelsa 0/6 2/6 0/6 3/511 I feel dizzyb 0/6 2/6 2/6 0/512 My head feels heavyb 0/6 2/6 2/6 0/513 Sweatinga 0/6 1/6 2/6 1/514 A thrill has gone through me...b 0/6 0/6 1/6 0/515 Vomitingc 0/6 0/6 0/6 1/5

16 Disorientationc 0/6 0/6 1/6 0/5

aItem included in the HRSb

Item included in the ARCIcSpontaneously reported


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unteers lose consciousness or contact with reality. Com-pared with the effects of intravenous (IV) DMT (Strass-man et al. 1994), clear differences were found in the in-tensity and duration of the experience. The slower onsetand longer duration of effects seen for ayahuasca can bereadily attributed to the oral route of administration forDMT and to the enzymatic blockade process (MAO inhi-bition) which mediates the drug's access to systemic cir-

culation. Additionally, the competition between DMTand increasing levels of serotonin for available receptorsites may contribute to an overall attenuation of effectsfrom ayahuasca vs IV administration of pure DMT.MAO inhibition not only allows for increased levels ofserotonin and other monoamines but also temporarilyblocks the immediate metabolism of DMT, thus extend-ing its action relative to its IV administration. The car-diovascular effects observed were milder than those re-ported for IV DMT (Strassman and Qualls 1994). Peakincreases of blood pressure and heart rate after aya-huasca were relatively delayed and comparable in mag-nitude to those brought about by a 0.10.2 mg/kg IV

DMT dose. Our cardiovascular values are in line withthose previously reported by Callaway and coworkers(1999) after an ayahuasca (hoasca) oral dose of 0.48 mgDMT/kg, though a direct comparison is not possible giv-en the non placebo-controlled nature of this earlier study.Considering the fact that in the present study elevationswere observed in cardiovascular parameter after placebo,it seems likely that the inclusion of a placebo control inthe earlier study could have rendered lower increases ofcardiovascular parameters for the 0.48 mg DMT/kg doseused. When compared with IV DMT, it is reasonable toassume that the reversible MAO-inhibiting properties ofharmine and harmaline leads to a transient increase in

endogenous monoamines, in addition to DMT's own car-diovascular effects. Nevertheless, the moderate nature ofthese increases could also be due to the simultaneous en-hancement of vagal activity induced by decreased sero-tonin metabolism. Additionally, ayahuasca seemed to in-duce more somatic-dysphoric effects than IV DMT, themost frequently reported being the modifications in bodyfeeling and nausea. These effects may be attributable tothe -carbolines present in the tea. A relationship be-tween the nausea and other distressing effects on the di-gestive tract and increased 5-HT levels has been postu-lated (Callaway et al. 1999).

Scorings on the six HRS subscales and the nature ofthe effects elicited by ayahuasca at the present low doseresembled those reported by Strassman et al. (1994) after0.1 mg/kg IV DMT. In both cases, somatic reactions pre-dominated over perceptual or cognitive effects. Scoreson the affect, volition, and intensity subscaleswere also close to those reported by Grob et al. (1996)after an ayahuasca dose equivalent to the low dose usedin the present study. Except for the perception andvolition subscales, which showed lower values, scoreson the HRS at the medium dose were greater than thosereported by Grob et al. (1996) and fell close to those de-scribed for 0.2 mg/kg IV DMT, a dosage known to be

fully psychoactive for DMT (Strassman et al. 1994).These differences probably indicate less overwhelmingperceptual effects and greater control over the experi-ence after ayahuasca. Finally, the five volunteers whoreceived the high dose (1.0 mg DMT/kg) identified it asbeing fully active and verbally described its effects asbeing very high in intensity. However, several subjec-tive-effect variables showed a saturation relative to the

0.75 mg DMT/kg dose. This saturation, or ceiling effect,may indicate an order effect due to the exploratory na-ture of the study design, with doses being administeredin an increasing order rather than in a randomized bal-anced manner. At the medium dose, scores on all HRSsubscales were higher than those reported by Grob et al.(1996) in their single-dose study. The cognition sub-scale for the medium dose in the present study scoredclose to the value obtained by Strassman et al. (1994) at0.4 mg/kg IV DMT, whereas scores on the other fivesubscales remained near those obtained after a 0.2 mg/kgIV DMT dose. Thus, not even at the 1.0 mg DMT/kg ay-ahuasca dose did the volunteers experience the over-

whelming effects reported for the highest dose used inStrassman's study (0.4 mg/kg IV), probably reflectingthe milder effects of DMT made orally active by meansof MAO inhibition.

Results obtained for the ARCI-A scale are indicativeof a subjective effect of increased activation. Despite thecoexistence of marked somatic-dysphoric effects, as re-flected by increases in the HRS-LSD scale, the adminis-tration of ayahuasca induced elevations in the ARCI-MBG scale, indicative of subjective feelings of well-being. The pleasant nature of the effects experienced byfive of the six volunteers was also reflected as increasesin the good effects, liking, and high VAS items,

especially at the high dose. On the contrary, sedation rat-ings, as reflected by the ARCI-PCAG scale did not reachstatistical significance and tended to decrease as the dos-es increased.

Regarding the similarities and differences of the ay-ahuasca experience with those elicited by other bettercharacterized serotonergic psychedelics, important dif-ferences can be found in the time course of effects.Ayahuasca effects are comparable in duration to those ofpsilocybin. On the other hand, mescaline and LSD areclearly longer-acting drugs, with peak effects at 35 hand an overall duration which can exceed 8 h (Strassman1994). Psychological effects are difficult to compare be-tween studies, due to the different psychometric instru-ments used. However, in a recent human study where theHRS was administered, psilocybin was found to induceincreases in all the HRS subscales, including volition.This greater impairment of the subjects' capacity to inter-act with themselves and their surroundings was furthercorroborated by their verbal reports, which describedsensations of loss of control and paranoid thoughts(Gouzoulis-Mayfrank et al. 1999a), neither of whichwere observed in the present study.

From a neurochemical perspective, data from precli-nical studies strongly support the involvement of seroto-

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nergic neurotransmission in the effects elicited by theclassic psychedelics, which includes DMT. Such com-pounds containing an indole moiety bind with high affin-ity to both the 5-HT2A and 5-HT1A sites in the humanbrain. A close correlation has been found between psy-chotropic potency and binding at the 5-HT2A site(Glennon et al. 1984) which is considered to be chieflyresponsible for the behavioral effects elicited by these

agents. The interaction with the 5-HT1A site has recentlybeen argued to modulate the intensity of the psychedelicexperience (Strassman 1996). Additionally, evidence of apossible long-term modulation of serotonergic neuro-transmission by ayahuasca has been reported in a previ-ous study, in which an apparent upregulation of theplatelet serotonin transporter was found in regular usersof the tea (Callaway et al. 1994). Nevertheless, the roleof dopaminergic involvement in the effects of the classicpsychedelics has also been examined. A recent PETstudy found that the administration of psilocybin to hu-man volunteers leads to the displacement of 11C-raclo-pride in the striatum, an effect that may reflect an in-

crease in dopamine release (Vollenweider et al. 1999).This secondary pro-dopaminergic activity may not be,however, the key to the perceptual and cognitive modifi-cations induced by these agents, as in another study psi-locybin's subjective effects were found to be increasedrather than reverted by the D2 receptor antagonist, halo-peridol, while they were effectively counteracted by ke-tanserin and risperidone (Vollenweider et al. 1998).

Neuroimaging studies have revealed patterns of in-creased metabolism throughout the brain, and more spe-cifically in the prefrontal cortices, particularly in theright hemisphere, in healthy volunteers after dosing withpsilocybin (Vollenweider et al. 1997; Gouzoulis-

Mayfrank et al. 1999b) and mescaline (Hermle et al.1992). In this respect, recent electrophysiological studieshave shown that 5-HT2A receptor activation by serotoninmediates an increase of excitatory postsynaptic poten-tials (EPSPs) and currents (EPSCs) in pyramidal neuronsof the neocortex and transitional cortex (Aghajanian andMarek 1997), an effect involving glutamate release andwhich is most pronounced in the medial prefrontal cortex(Marek and Aghajanian 1998a, b). These findings sug-gest an excitatory action of the classic psychedelics onthe human frontal and parietal cortices and in the prima-ry auditory and visual areas, which show very high den-sities of 5-HT2A sites (Pazos et al. 1987). This excitatoryeffect may account for the enhancement and modifica-tions of auditory and visual perception described by thevolunteers. An analogous excitatory action on the so-matosensory and visual association areas, both showinghigh 5-HT2A densities, may also play a role in the pecu-liar modifications of perception brought about by ay-ahuasca. Finally, the activation of the anterior cingulatecortex (ACC), an area also showing dense serotonergicinnervation and 5-HT2A sites, could contribute to theemotional overtones of the ayahuasca experience. A re-cent PET study has implicated the ACC in normal emo-tional awareness (Lane et al. 1998), and psilocybin ad-

ministration leads to increases in metabolism in this area,where 5-HT2A-mediated EPSPs/EPSCs have also beenrecorded (Aghajanian and Marek 1997).

To summarize, ayahuasca induced a modified state ofawareness in which stimulatory and psychedelic effectswere present, and increased in a dose-dependent manner.The volunteers experienced modifications in perceptionand thought processes, such as rapid succession of

thoughts, visions, and recollections of recent events, fre-quently having a marked emotional content. Ayahuascawas safely administered to the volunteers in this studyand its effects were regarded as pleasant and desirable,except for one volunteer who experienced a dysphoricstate that was characterized by transient disorientationand anxiety. Nevertheless, this adverse reaction wasmost likely related to the limited previous experience ofthat volunteer with the tea. Finally, the nature of the ex-perience produced by ayahuasca resembled that of IVDMT, though it was less overwhelming, of longer dura-tion, and displayed a greater variety of somatic-dyspho-ric effects. Moderate actions on blood pressure and heart

rate were found and no clinically relevant changes wereobserved in biochemical parameters after any of the ex-perimental sessions. Future studies will include measuresof sensorimotor gating and brain imaging techniques inlarger volunteer groups, using a double-blind balanceddesign, in order to obtain additional information on themechanisms underlying the central effects ofayahuasca.

Acknowledgements We would like to express our gratitude toEsther Martnez, Flix Gonzlez, and Jos Mara Fbregas fortheir continued support and help in contacting the people at CE-FLURIS in Brazil, and to the latter for agreeing to submit their ay-ahuasca (Daime) for evaluation in a clinical trial. Thanks are alsodue to Sylvie Cotxet and David Martnez for their assistance dur-ing data collection. Finally, we greatly acknowledge the assistance

of Ignasi Gich for his helpful comments on data analysis and revi-sion of the manuscript. This work was supported by grant IR-97/034/980 from the Institut de Recerca HSCSP.

References

Aghajanian GK, Marek GJ (1997) Serotonin induces excitatorypostsynaptic potentials in apical dendrites of neocortical pyra-midal cells. Neuropharmacology 36:589599

Callaway JC, Grob CS (1998) Ayahuasca preparations and seroto-nin reuptake inhibitors: a potential combination for severe ad-verse interactions. J Psychoactive Drugs 30:367369

Callaway JC, Airaksinen MM, McKenna DJ, Brito GS, Grob CS(1994) Platelet serotonin uptake sites increased in drinkers of

ayahuasca. Psychopharmacology 116:385387Callaway JC, Raymon LP, Hearn WL, McKenna DJ, Grob CS,Brito GC, Mash DC (1996) Quantitation ofN,N-dimethyltryp-tamine and harmala alkaloids in human plasma after oral dos-ing with Ayahuasca. J Anal Toxicol 20:492487

Callaway JC, McKenna DJ, Grob CS, Brito GS, Raymon LP,Poland RE, Andrade EN, Andrade EO, Mash DC (1999) Phar-macology of hoasca alkaloids in healthy humans. J Ethnophar-macol 65:243256

Deliganis A, Pierce P, Peroutka S (1991) Differential interactionsof dimethyltryptamine (DMT) with 5-HT1A and 5-HT2 recep-tors. Biochem Pharmacol 41:17391744

Dobkin de Ros M (1972) Visionary vine: hallucinogenic healingin the Peruvian Amazon. Chandler Publishing, San Francisco

94


12/12

Ott J (1999) Pharmahuasca: human pharmacology of oral DMTplus harmine. J Psychoactive Drugs 31:171177

Pazos A, Probst A, Palacios JM (1987) Serotonin receptors in thehuman brain. IV. Autoradiographic mapping of serotonin-2 re-ceptors. Neuroscience 21:123139

Pierce P, Peroutka S (1989) Hallucinogenic drug interactions withneurotransmitter receptor binding sites in human cortex. Psy-chopharmacology 97:118122

Riba J, Rodrguez-Fornells A, Strassman RJ, Barbanoj MJ (2000)Psychometric assessment of the Hallucinogen Rating Scale.

Drug Alcohol Depend (in press)Rivier L, Lindgren J (1972) Ayahuasca, the South American hallu-cinogenic drink: ethnobotanical and chemical investigations.Econ Bot 29:101129

Schultes RE, Hofmann A (1980) The botany and chemistry of hal-lucinogens. Thomas, Springfield, Illinois

Schultes RE, Hofmann A (1982) Plantas de los dioses: orgenesdel uso de los alucingenos. Fondo de Cultura Econmica,Mxico D.F.

Spielberger CD, Gorsuch RL, Lushene RE (1970) Manual for thestate-trait anxiety inventory. Consulting Psychologists Press,Palo Alto, California

Strassman RJ (1994) Human psychopharmacology of LSD, di-methyltryptamine and related compounds. In: Pletscher A,Ladewig D (eds) 50 years of LSD: current status and perspec-tives of hallucinogens. Parthenon, London

Strassman RJ (1996) Human psychopharmacology ofN,N-dimeth-yltryptamine. Behav Brain Res 73:121124Strassman RJ, Qualls CR (1994) Dose response study ofN,N-di-

methyltryptamine in humans. I. Neuroendocrine, autonomicand cardiovascular effects. Arch Gen Psychiatry 51:98108

Strassman RJ, Qualls CR, Uhlenhuth EH, Kellner R (1994) Doseresponse study ofN,N-dimethyltryptamine in humans. II. Sub- jective effects and preliminary results of a new rating scale.Arch Gen Psychiatry 51:98108

Suzuki O, Katsumata Y, Oya M (1981) Characterization of eightbiogenic indoleamines as substrates for type A and type Bmonoamine oxidase. Biochem Pharmacol 30:13531358

Vollenweider FX, Leenders KL, Scharfetter C, Maguire P, Stadel-mann O, Angst J (1997) Positron emission tomography andfluorodeoxyglucose studies of metabolic hyperfrontality andpsychopathology in the psilocybin model of psychosis. Neuro-

psychopharmacology 16:357372Vollenweider FX, Vollenweider-Scherpenhuyzen MF, Babler A,Vogel H, Hell D (1998) Psilocybin induces schizophrenia-likepsychosis in humans via serotonin-2 agonist action. Neurore-port 9:38973902

Vollenweider FX, Vontobel P, Hell D, Leenders KL (1999) 5-HTmodulation of dopamine release in basal ganglia in psilocybin-induced psychosis in man. A PET study with [11C]raclopride.Neuropsychopharmacology 20:424433

95

Glennon RA, Titeler M, McKenney JD (1984) Evidence for 5-HT2involvement in the mechanism of action of hallucinogenicagents. Life Sci 35:25052511

Gouzoulis-Mayfrank E, Thelen B, Habermeyer E, Kunert HJ,Kovar KA, Lindenblatt H, Hermle L, Spitzer M, Sass H(1999a) Psychopathological, neuroendocrine and autonomiceffects of 3,4-methylenedioxyethylamphetamine (MDE), psi-locybin and d-methamphetamine in healthy volunteers. Psy-chopharmacology 142:4150

Gouzoulis-Mayfrank E, Schreckenberger M, Sabri O, Arning C,

Thelen B, Spitzer M, Kovar KA, Hermle L, Bll U, Sass H(1999b) Neurometabolic effects of psilocybin, 3,4-methyle-nedioxyethylamphetamine (MDE) and d-methamphetamine inhealthy volunteers. A double-blind, placebo-controlled PETstudy with [18F]FDG. Neuropsychopharmacology 20:565581

Grob CS, McKenna DJ, Callaway JC, Brito GS, Neves ES,Oberlaender G, Saide OL, Labigalini E, Tacla C, Miranda CT,Strassman RJ, Boone KB (1996) Human psychopharmacologyof hoasca, a plant hallucinogen used in ritual context in Brazil.J Nerv Ment Dis 184:8694

Hermle L, Fnfgeld M, Oepen G, Botsch H, Borchardt D,Gouzoulis E, Fehrenbach RA, Spitzer M (1992) Mescaline-in-duced psychopathological, neuropsychological, and neuromet-abolic effects in normal subjects: experimental psychosis as atool for psychiatric research. Biol Psychiatry 32:976991

Lamas X, Farr M, Llorente M, Cam J (1994) Spanish version of

the 49-item short form of the Addiction Research Center in-ventory. Drug Alcohol Depend 35:203209Lane RD, Reiman EM, Axelrod B, Lang-Sheng Y, Holmes A,

Schwartz GE (1998) Neural correlates of levels of emotionalawareness. Evidence of an interaction between emotion andattention in the anterior cingulate cortex. J Cogn Neurosci10:525535

Liwszyc GE, Vuori E, Rasanen I, Issakainen J (1992) Daime aritual herbal potion. J Ethnopharmacol 36:9192

Lpez P (1999) Ayahuasca, el ltimo alucine. Tiempo 910:2628Marek GJ, Aghajanian GK (1998a) The electrophysiology of pre-

frontal serotonin systems: therapeutic implications for moodand psychosis. Biol Psychiatry 44:11181127

Marek GJ, Aghajanian GK (1998b) Indoleamine and the pheneth-ylamine hallucinogens: mechanisms of psychotomimetic ac-tion. Drug Alcohol Depend 51:189198

Marshall J (1997) Daimismo, la comunin con la ayahuasca. Inte-gral 1:1623McKenna DJ, Towers GHN, Abbott F (1984) Monoamine oxidase

inhibitors in South American hallucinogenic plants: trypt-amine and beta-carboline constituents ofayahuasca. J Ethno-pharmacol 10:195223

Metzner R (1999) Amazonian vine of visions. In: Metzner R (ed)Ayahuasca. Hallucinogens, consciousness and the spirit of na-ture. Thunder's Mouth Press, New York

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Subjective effects and tolerability of the South American psychoactive beverage Ayahuasca in healthy volunteers