Participants were recruited from the Baltimore, MD area through flyers and ads in local newspapers. After a phone screen confirmed basic inclusion criteria (age, high-school-level education, and prior hallucinogen use), volunteers came to the laboratory for in-person screening. A social worker (who was trained by psychometricians and had a psychiatrist and clinical psychologist available for consultation) conducted a structured clinical interview to exclude individuals with a current or past history of meeting DSM-IV criteria for schizophrenia; psychotic disorder (unless substance-induced or due to a medical condition); bipolar I or II disorder; alcohol or drug dependence (excluding caffeine and nicotine) for the last 5 years; severe major depression; dissociative disorder; and other psychiatric conditions judged to be incompatible with establishment of rapport or safe exposure to hallucinogens. Participants were excluded who reported having a first or second degree relative with schizophrenia, psychotic disorder (unless substance induced or due to a medical condition), or bipolar I or II disorder. Medical evaluation included a physical exam conducted by a nurse practitioner, an ECG evaluated by a physician, and a physician evaluation of blood sample analyses that included a complete blood count with differential and a chemistry panel including electrolytes, glucose, urea, creatinine, uric acid, liver profile, total cholesterol, and triglycerides. Additional screening visits assessed general motivation for participation and established trust and rapport with the study staff. Participants agreed to refrain from using S. divinorum or illicit drugs during the course of the study.
Four participants (M = 29.5 years old, range = 23 – 35 years old; 2 females) passed screening and completed all drug sessions and data collection (Note: One additional individual participated in pilot sessions to develop and refine the inhalation procedure; these data are not included in the reported analyses). Participant bodyweights were 58.5, 74.6, 64.4, and 67.1 kg for the two males and two females, respectively. Participants had at least a high-school level of education (M = 15 years, range = 14 – 16 years) reported using S. divinorum at least once in the past five years (M = 16 uses, range = 2 – 40 uses). Participants were compensated $50 per session (plus a bonus of $50 per session upon completion of data collection). Participations were also motivated by their reported interest in spirituality and/or altered states of consciousness. Transportation to and from the study site (via taxi) was provided for all participants. The Institutional Review Board of the Johns Hopkins University School of Medicine approved the study, and all participants gave their informed consent before participation.
2.2 Drug preparation and delivery device
Salvinorin A was isolated from S. divinorum leaves and shown to be 99.5 % pure by HPLC. Because weighing the very small doses of salvinorin A required for this study is difficult, a larger quantity was weighed on an analytical balance and then dissolved in a measured volume of HPLC grade acetone. After filtering through a sterilized, acetone-approved 0.2 μm filter (Millex-LG Filter Unit, Millipore Corporation, Billerica, MA), 1 ml of solution was placed into a 5 ml round bottom chemistry flask and allowed to evaporate, leaving the dose of salvinorin A as a residue on the interior surface of the flask. Before the session, the flask was attached to the bottom of a chemistry vacuum adapter by ground glass tapered joint and secured by a metal Keck clip. A vinyl tube (23 cm long, 6.35 mm inside diameter) was connected to the vacuum line of the adapter for inhalation. The tubing was replaced between participants but was not replaced for different sessions for the same participant. The resulting “pipe” was held stable by a ring stand clamp during administration, and the tube extended through a hole in a room divider toward the participant’s sitting area.
2.3 Drug administration
Sixteen doses of salvinorin A were administered in an ascending order. Although it is unknown whether salvinorin A effects are bodyweight dependent, doses in this study were adjusted for participant bodyweight based on knowledge that some but not all psychoactive drug effects are bodyweight dependent. The lowest dose in the sequence was 0.375 μg/kg of bodyweight and subsequent doses were 0.75 μg/kg, 1.5μg/kg, and thereafter increased by an increment of 1.5 μg/kg until the maximum dose of 21 μg/kg was reached. Four placebo doses were inserted in the ascending sequence of salvinorin A doses such that each consecutive block of 5 sessions included 1 placebo. The position of the single placebo within each block of 5 sessions was determined randomly for each volunteer. Participants were told that on any session they may receive a dose of salvinorin A or placebo but were not told about the ascending design or frequency of placebos.
For each session the round-bottom flask was heated from underneath with a butane microtorch with approximate flame temperature of 1,700 °C (model ST200T, Bernzomatic, Huntersville, NC). Although the boiling point and combustion temperature of salvinorin A have not been empirically determined, the flame temperature was assumed to be sufficient to heat the salvinorin A on the interior of the flask to its boiling point during the decreased air pressure created by inhalation, without substantial combustion of salvinorin A. The microtorch was adjusted so that the flame was approximately 1.5 cm in length, and the tip of the flame was held in contact with the round-bottom flask. Using these procedures, inhalation of un-volatilized drug was unlikely because the salvinorin A residue left upon evaporation of acetone appeared strongly attached to the interior of the flask, and in tests with various rates of mechanical airflow (simulated inhalation) without heat, salvinorin A was observed to remain undisturbed. Tests with mechanical airflow and the application of the microtorch showed the method to result in the volatilization of salvinorin A with little scorching (small black marks presumably resulting from combustion). Seated in a comfortable reclining lounger, the participant inhaled slowly for 40 s while the flask was heated, followed by a verbally cued exhale. For placebo sessions, the same protocol was followed but no salvinorin A was in the flask. The unblinded session monitor who heated the flask was obscured from the participant’s view (behind the divider), while the blinded staff member collected drug-strength ratings and all other pre- and post-session data from the participant.
2.4 Drug sessions
Each participant completed 20 sessions across several weeks (range = 8 – 14 weeks). Participants typically completed 1 – 3 sessions per week with consecutive sessions separated by at least 1 day (range = 1 day to 4.5 weeks).
Each meeting at the study site lasted approximately 2.5 hours. Upon arrival, participants provided an expired air sample that was required to indicate a blood alcohol concentration of 0.00% for the session to continue (Alco-Sensor IV, Intoximeters, Inc., Saint Louis, MO). In addition, abstinence from opioids, cocaine, and benzodiazepines was confirmed by urine test before each session (model MUI-PM, Medimpex United Inc., Bensalem, PA). This urine test panel was selected because it can detect opioids such as oxycodone and buprenorphine with kappa opioid effects. Abstinence from hallucinogens (and other drugs not listed above) was not biologically confirmed. However, participants consented to have their urine tested for “various drugs” and were not informed about which drugs were included in the urine test. Female participants were required to provide a negative urine pregnancy test before each session (model HCG-001, Medimpex United Inc., Bensalem, PA). Also before drug administration, participants briefly reviewed experiences from the last session with the study staff. During drug administration, participants were seated in a comfortable semi-upright or reclined position and wore eyeshades for 3–5 minutes before and for 10–30 minutes after drug administration. A relaxing instrumental music track (Steven Halpern, “Awakening”, Music for Sound Healing, Inner Peace Music, 1999) was played throughout the session as a continuous loop. Approximately 1 hour after drug administration participants completed several questionnaires and computer-based assessments (duration = 45–60 minutes).
Blood pressure (systolic and diastolic using oscillometric method with the blood pressure cuff placed on the arm) and heart rate were monitored using a Non-Invasive Patient Monitor Model 507E (Criticare Systems, Waukesha, WI). Data were collected at baseline (for at least 5 minutes before drug administration) and every 2 minutes during the 60 minutes following drug administration.
Participants indicated overall drug strength using an 11-point scale (0 = definitely no effect; 1 or 2 = possible salvinorin A effects; 3–10 = definite salvinorin A effects with 10 representing “the strongest effect imaginable for salvinorin A”). Participants were verbally cued to provide a rating of drug strength at baseline and every 2 minutes for 60 minutes after drug administration. In the case of missing reports (i.e., participant unresponsive during the first few minutes of drug effects), the value of ‘10’ was imputed.
2.5.3 Safety and tolerability
Although not reported by users in retrospective analyses (Baggott et al., 2010
; González et al., 2006
), tremor has been observed in rhesus monkeys at a substantially higher dose (100 μg/kg) than our maximum dose (Butelman; personal communication, 2006). The Fahn-Tolosa-Marin Tremor Rating Scale (TRS; Fahn et al., 1993
) was used to classify resting and kinetic tremor severity on a 5-point scale. At baseline and at 15 and 30 minutes after drug administration, the study staff visually assessed kinetic tremor intensity as the participant bent both of his or her extended arms to touch middle finger to nose. Study staff also rated the magnitude of resting tremor during the time interval leading up to the assessments of kinetic tremor (i.e., 0–15 min, 15–30 min) by closely observing the participant.
To assess psychological effects that might warrant discontinuing future sessions, participants were asked at the end of each session “Would you absolutely refuse to receive the same or higher dose of today’s drug in future sessions?” A “no” response was required to continue. In addition, study staff interviewed the participant before and after each session to determine how s/he felt about continuing to participate.
2.5.4 End-of-session subject-rated effects
Shortly after the 60-minute time point, participants were asked to retrospectively rate the strength of the peak drug effect during the session using the same 11-point scale used to assess the time course of drug effects. Because kappa opioid agonists, including salvinorin A, have been reported to induce dysphoric effects (Walsh et al., 2001
; González et al., 2006
), participants were asked to complete retrospective ratings of “drug liking” and “drug disliking” (2 questions; 0= neutral or no effect, 1=like/dislike but not very much, 2=like/dislike somewhat, 3= like/dislike quite a bit, 4=like/dislike very much), and “good effects” and “bad effects” (2 questions; 0= no good/bad effects at all, 1= a little, 2= moderately, 3=quite a bit, 4=very much).
Consistent with case reports and survey studies of S. divinorum
users (Siebert, 1994
; Baggott et al., 2010
; Bücheler et al., 2005
; González et al., 2006
) we hypothesized that salvinorin A would elicit subjective effects with substantial overlap with classic hallucinogens (e.g., psilocybin, LSD). We further hypothesized that, unlike orally administered psilocybin and LSD, volatilized and inhaled salvinorin A would have a timecourse profile more similar to intravenous dimethyltryptamine (Strassman et al., 1994
). In addition, because S. divinorum
has been used by shamans for divination and “visionary effects” (Ott, 1995
), we hypothesized that salvinorin A might elicit subject-rated mystical-type effects. We used two questionnaires to assess these effects. The Hallucinogen Rating Scale (HRS; 99 items) was designed to show sensitivity to dimethyltryptamine (Strassman et al., 1994
) and has also been shown sensitive to psilocybin (Griffiths et al., 2006
). It consists of six subscales assessing various aspects of hallucinogen effects: Intensity (effects related to the strength of the overall experience), Somaesthesia (interoceptive, visceral and tactile effects), Affect (emotional and affective responses), Perception (visual, auditory, gustatory, and olfactory effects), Cognition (alterations in thought processes or content), and Volition (awareness of the environment and capacity to willfully control one’s body). Most items are rated on a 5-point scale (0 = not at all; 4 = extremely). The Mysticism Scale (32 items) was developed to assess primary mystical or spiritual experiences (Hood et al., 2001
) and has been shown to be sensitive to the effects of psilocybin (Griffiths et al., 2006
). Each item is rated on a 9-point scale (−4 = this description is extremely not true of my own experience; 0 = I cannot decide; +4 = this description is extremely true of my own experience). Approximately 1 hour after drug administration, participants completed the HRS and Mysticism Scale with reference to their experiences since receiving the inhaled drug.
Subject-rated drug strength ratings collected throughout the timecourse were used to calculate, for individual participant, area under the curve (AUC) values using the trapezoidal rule. Repeated measures analysis of variance (ANOVA) with within-subjects factor of dose (17 dose levels including placebo) was used to examine dose-related changes in the subject-rated measures and physiology (peak heart rate and blood pressure). For each participant, drug strength ratings across the 4 placebo sessions were averaged to create a single placebo data point. Tukey’s HSD tests were conducted to compare dose levels, with family-wise error rate maintained at α = .05.