Pharmacokinetics, pharmacodynamics and urinary recovery of oral lysergic acid diethylamide administration in healthy participants.

AIMS: Lysergic acid diethylamide (LSD) is currently investigated for several neurological and psychiatric illnesses. Various studies have investigated the pharmacokinetics and the pharmacokinetic-pharmacodynamic relationship of LSD in healthy participants, but data on urinary recovery and confirmatory studies are missing. METHODS: The present study characterized the pharmacokinetics, pharmacokinetic-pharmacodynamic relationship and urinary recovery of LSD at doses of 85 and 170 µg administered orally in 28 healthy participants. The plasma concentrations and subjective effects of LSD were continuously evaluated over a period of 24 h. Urine was collected during 3 time intervals (0-8, 8-16 and 16-24 h after LSD administration). Pharmacokinetic parameters were determined using compartmental modelling. Concentration-subjective effect relationships were described using pharmacokinetic-pharmacodynamic modelling. RESULTS: Mean (95% confidence interval) maximal LSD concentrations were 1.8 ng/mL (1.6-2.0) and 3.4 ng/mL (3.0-3.8) after the administration of 85 and 170 µg LSD, respectively. Maximal concentrations were achieved on average after 1.7 h. Elimination half-lives were 3.7 h (3.4-4.1) and 4.0 h (3.6-4.4), for 85 and 170 µg LSD, respectively. Only 1% of the administered dose was recovered from urine unchanged within the first 24 h, 16% was eliminated as 2-oxo-3-hydroxy-LSD. Urinary recovery was dose proportional. Mean (±standard deviation) durations of subjective effects were 9.3 ± 3.2 and 11 ± 3.7 h, and maximal effects (any drug effects) were 77 ± 18% and 87 ± 13% after 85 and 170 µg of LSD, respectively. CONCLUSION: The present novel study validates previous findings. LSD exhibited dose-proportional pharmacokinetics and first-order elimination kinetics and dose-dependent duration and intensity of subjective effects. LSD is extensively metabolized and shows dose-proportional urinary recovery.

Acute dose-dependent effects of mescaline in a double-blind placebo-controlled study in healthy subjects.

Classic psychedelics have regained interest in research and therapy. Despite the long tradition of the human use of mescaline, modern data on its dose-dependent acute effects and pharmacokinetics are lacking. Additionally, its mechanism of action has not been investigated in humans. We used a randomized, double-blind, placebo-controlled, crossover design in 16 healthy subjects (8 women) who received placebo, mescaline (100, 200, 400, and 800 mg), and 800 mg mescaline together with the serotonin 5-hydroxytryptamine-2A (5-HT2A) receptor antagonist ketanserin (40 mg) to assess subjective effects, autonomic effects, adverse effects, and pharmacokinetics up to 30 h after drug administration. Mescaline at doses >100 mg induced dose-dependent acute subjective effects. Mescaline increased systolic and diastolic blood pressure at doses >100 mg, with no difference between doses of 200-800 mg. Heart rate increased dose-dependently. Pharmacokinetics of mescaline were dose-proportional. Maximal concentrations were reached after approximately 2 h, and the plasma elimination half-life was approximately 3.5 h. The average duration of subjective effects increased from 6.4 to 14 h with increasing doses of 100-800 mg mescaline. Nausea and emesis were frequent adverse effects at the 800 mg dose. Co-administration of ketanserin attenuated and shortened acute effects of 800 mg mescaline to become comparable to the 100 and 200 mg doses. There were no ceiling effects of the subjective response within the investigated dose range, but tolerability was lower at the highest doses. These results may assist with dose finding for future research and suggest that acute effects of mescaline are primarily mediated by 5-HT2A receptors.

Acute effects of intravenous DMT in a randomized placebo-controlled study in healthy participants.

N,N-dimethyltryptamine (DMT) is distinct among classic serotonergic psychedelics because of its short-lasting effects when administered intravenously. Despite growing interest in the experimental and therapeutic use of intravenous DMT, data are lacking on its clinical pharmacology. We conducted a double-blind, randomized, placebo-controlled crossover trial in 27 healthy participants to test different intravenous DMT administration regimens: placebo, low infusion (0.6 mg/min), high infusion (1 mg/min), low bolus + low infusion (15 mg + 0.6 mg/min), and high bolus + high infusion (25 mg + 1 mg/min). Study sessions lasted for 5 h and were separated by at least 1 week. Participant's lifetime use of psychedelics was ≤20 times. Outcome measures included subjective, autonomic, and adverse effects, pharmacokinetics of DMT, and plasma levels of brain-derived neurotropic factor (BDNF) and oxytocin. Low (15 mg) and high (25 mg) DMT bolus doses rapidly induced very intense psychedelic effects that peaked within 2 min. DMT infusions (0.6 or 1 mg/min) without a bolus induced slowly increasing and dose-dependent psychedelic effects that reached plateaus after 30 min. Both bolus doses produced more negative subjective effects and anxiety than infusions. After stopping the infusion, all drug effects rapidly decreased and completely subsided within 15 min, consistent with a short early plasma elimination half-life (t1/2α) of 5.0-5.8 min, followed by longer late elimination (t1/2ß = 14-16 min) after 15-20 min. Subjective effects of DMT were stable from 30 to 90 min, despite further increasing plasma concentrations, thus indicating acute tolerance to continuous DMT administration. Intravenous DMT, particularly when administered as an infusion, is a promising tool for the controlled induction of a psychedelic state that can be tailored to the specific needs of patients and therapeutic sessions.Trial registration: ClinicalTrials.gov identifier: NCT04353024.

Liquid chromatography-tandem mass spectrometry method for the bioanalysis of N,N-dimethyltryptamine (DMT) and its metabolites DMT-N-oxide and indole-3-acetic acid in human plasma.

The indole alkaloid N,N-dimethyltryptamine (DMT) induces psychedelic effects in humans. In addition to ceremonial and recreational use, DMT is subject to clinical investigations. Sensitive bioanalytical methods are required to assess the pharmacokinetics of DMT and its metabolites in human plasma. Here, a high performance liquid chromatography-tandem mass spectrometry (LC-MS/MS) method for the quantification of DMT and its major metabolites indole-3-acetic acid (IAA) and DMT-N-oxide (DMT-NO) was developed and validated. As IAA is an endogenous component of human plasma, 13C6-IAA was used to determine IAA concentrations. After simple protein precipitation with methanol, analytes were separated on a pentafluorophenyl column. A gradient consisting of 0.1% (v/v) formic acid in a methanol-water mixture was applied for analyte separation. The analytes were detected by positive electrospray ionization followed by multiple reaction monitoring. The calibration range of the assay was 0.25-250 ng/mL for DMT, 0.1-100 ng/mL for DMT-NO, and 25-25,000 ng/mL for 13C6-IAA. The intra- and inter-assay accuracy was 93-113% for all analytes at all quality control levels, with coefficient of variation ≤ 11%. All analytes were stable under storage conditions relevant for the analysis of large batches of study samples. The validated method was capable of assessing pharmacokinetic (PK) parameters of DMT and its metabolites in study participants intravenously perfused with 1 mg/min DMT for 90 min. Overall, the developed method is easy-to-use, has a short run time, and qualifies for PK and metabolism studies of DMT in clinical settings.