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Chronic pain and psychedelics: a review and proposed mechanism of action

Abstract

The development of chronic pain is a complex mechanism that is still not fully understood. Multiple somatic and visceral afferent pain signals, when experienced over time, cause a strengthening of certain neural circuitry through peripheral and central sensitization, resulting in the physical and emotional perceptual chronic pain experience. The mind-altering qualities of psychedelics have been attributed, through serotonin 2A (5-HT2A) receptor agonism, to ‘reset’ areas of functional connectivity (FC) in the brain that play prominent roles in many central neuropathic states. Psychedelic substances have a generally favorable safety profile, especially when compared with opioid analgesics. Clinical evidence to date for their use for chronic pain is limited; however, several studies and reports over the past 50 years have shown potential analgesic benefit in cancer pain, phantom limb pain and cluster headache. While the mechanisms by which the classic psychedelics may provide analgesia are not clear, several possibilities exist given the similarity between 5-HT2A activation pathways of psychedelics and the nociceptive modulation pathways in humans. Additionally, the alterations in FC seen with psychedelic use suggest a way that these agents could help reverse the changes in neural connections seen in chronic pain states. Given the current state of the opioid epidemic and limited efficacy of non-opioid analgesics, it is time to consider further research on psychedelics as analgesics in order to improve the lives of patients with chronic pain conditions.
Castellanos, J. P., Woolley, C., Bruno, K. A., Zeidan, F., Halberstadt, A., & Furnish, T. (2020). Chronic pain and psychedelics: a review and proposed mechanism of action. Regional Anesthesia & Pain Medicine., http://dx.doi.org/10.1136/rapm-2020-101273
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The Viability of Microdosing Psychedelics as a Strategy to Enhance Cognition and Well-being – An Early Review

Abstract

Psychedelic substances are currently experiencing a renaissance in interest for both therapeutic as well as recreational applications. It has been proposed that microdosing, i.e., ingesting sub-perceptual doses of a psychedelic, could confer some of the benefits of these substances to users while minimizing the risks associated with full-dose use. This review aimed to summarize and examine the extant literature on psychedelic microdosing. Exploratory evidence published to date indicates a variety of benefits reported by microdosers including improvements in mood, focus, and creativity, with some null reports, and a minority of people reporting selective negative consequences such as increased anxiety and physiological discomfort. Methodological limitations of current evidence, however, make definitive conclusions hard to draw. Recommendations for future research are given.
Bornemann, J. (2020). The Viability of Microdosing Psychedelics as a Strategy to Enhance Cognition and Well-being-An Early Review. Journal of Psychoactive Drugs, 1-9., https://doi.org/10.1080/02791072.2020.1761573
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Psychedelics and Psychedelic-Assisted Psychotherapy

Abstract

Objective: The authors provide an evidenced-based summary of the literature on the clinical application of psychedelic drugs in psychiatric disorders.
Methods: Searches of PubMed and PsycINFO via Ovid were conducted for articles in English, in peer-reviewed journals, reporting on “psilocybin,” “lysergic acid diethylamide,” “LSD,” “ayahuasca,” “3,4-methylenedioxymethamphetamine,” and “MDMA,” in human subjects, published between 2007 and July 1, 2019. A total of 1,603 articles were identified and screened. Articles that did not contain the terms “clinical trial,” “therapy,” or “imaging” in the title or abstract were filtered out. The 161 remaining articles were reviewed by two or more authors. The authors identified 14 articles reporting on well-designed clinical trials investigating the efficacy of lysergic acid diethylamide (LSD), 3,4-methylenedioxymethamphetamine (MDMA), psilocybin, and ayahuasca for the treatment of mood and anxiety disorders, trauma and stress-related disorders, and substance-related and addictive disorders as well as in end-of-life care.
Results: The most significant database exists for MDMA and psilocybin, which have been designated by the U.S. Food and Drug Administration (FDA) as “breakthrough therapies” for posttraumatic stress disorder (PTSD) and treatment-resistant depression, respectively. The research on LSD and ayahuasca is observational, but available evidence suggests that these agents may have therapeutic effects in specific psychiatric disorders.
Conclusions: Randomized clinical trials support the efficacy of MDMA in the treatment of PTSD and psilocybin in the treatment of depression and cancer-related anxiety. The research to support the use of LSD and ayahuasca in the treatment of psychiatric disorders is preliminary, although promising. Overall, the database is insufficient for FDA approval of any psychedelic compound for routine clinical use in psychiatric disorders at this time, but continued research on the efficacy of psychedelics for the treatment of psychiatric disorders is warranted.

Keywords: Ayahuasca; Drug-Psychotherapy Combination; Lysergic Acid Diethylamide; MDMA; Psilocybin; Psychedelics.
Reiff, C. M., Richman, E. E., Nemeroff, C. B., Carpenter, L. L., Widge, A. S., Rodriguez, C. I., … & Work Group on Biomarkers and Novel Treatments, a Division of the American Psychiatric Association Council of Research. (2020). Psychedelics and psychedelic-assisted psychotherapy. American Journal of Psychiatry177(5), 391-410., https://doi.org/10.1176/appi.ajp.2019.19010035
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Ayahuasca – potential therapeutic properties in psychiatry. Research review

Abstract

Ayahuasca, also known as “the liana of the soul” and “the vine of the soul” is a ritual psychedelic traditionally administered in the form of plant decoction, used by the indigenous people of South America for centuries, and in the last 25 years also in Europe, Asia, Africa, Australia, Canada, and the United States. Its biological activity results from the content of N,N-dimethyltryptamine (DMT), acting mainly as a non-selective agonist of serotonin receptors and beta-carboline alkaloids, which are strong and short-acting monoamine oxidase type A(MAOI-A) inhibitors. For many years there have been reports of both the anti-anxiety and antidepressant effects of ayahuasca, as well as indications of the possibility of its use in the treatment of addictions. The results of studies of its effectiveness in drug-resistant depression seem to be promising, comparable in the opinion of some authors with the effect of therapeutic action of ketamine. In the article, we try to explain the complex profile of action and the resulting potential benefits, but also the risk of interaction and adverse effects associated with the taking of ayahuasca, which is important given the high variability of herbal mixtures used to produce the decoction.

Barabasz-Gembczyk, A., & Kucia, K. (2020). Ayahuasca–potential therapeutic properties in psychiatry. Research review. Psychiatr. Pol.. Pol54(2), 381-389., https://doi.org/10.12740/PP/103364
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Stability Evaluation of DMT and Harmala Alkaloids in Ayahuasca Tea Samples

Abstract

Ayahuasca tea is a hallucinogenic beverage used for religious purposes in Brazil and many other countries that has therapeutic potential in the treatment of some mental health disorders. In the context of psychedelic research, quantification of the tea’s main alkaloids prior to its administration in animal or human studies is essential. For this reason, this study aims to provide information regarding the stability of the main ayahuasca alkaloids (dimethyltryptamine, DMT; harmine, HRM; tetrahydroharmine, THH; harmaline, HRL) in three different conditions: (1) A year stored in a refrigerator either in plastic or glass containers, (2) seven days at 37 °C to reproduce usual mail transportation, and (3) after three freeze-thaw cycles. Samples were quantified after a dilute-and-shoot procedure using liquid chromatography tandem mass spectrometry (LC-ESI-MS/MS). There was no significant degradation of DMT concentration over time in all tested conditions. Harmala alkaloids (THH, HRL, and HRM) showed important variations after long-term and high-temperature storages. Although DMT has proven to be stable in all studied conditions, the harmala alkaloids revealed intense degradation and even concentration increment. This may be caused by degradation, alkaloid inter-conversion, and leaching from tea precipitate material. Therefore, ayahuasca quantification before administration in controlled sets is mandatory.

de Oliveira Silveira, G., Guimarães Dos Santos, R., Rebello Lourenço, F., Novak Rossi, G., Hallak, J., & Yonamine, M. (2020). Stability Evaluation of DMT and Harmala Alkaloids in Ayahuasca Tea Samples. Molecules (Basel, Switzerland), 25(9), 2072. https://doi.org/10.3390/molecules25092072

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A Single Administration of the Atypical Psychedelic Ibogaine or Its Metabolite Noribogaine Induces an Antidepressant-Like Effect in Rats

Abstract

Anecdotal reports and open-label case studies in humans indicated that the psychedelic alkaloid ibogaine exerts profound antiaddictive effects. Ample preclinical evidence demonstrated the efficacy of ibogaine, and its main metabolite, noribogaine, in substance-use-disorder rodent models. In contrast to addiction research, depression-relevant effects of ibogaine or noribogaine in rodents have not been previously examined. We have recently reported that the acute ibogaine administration induced a long-term increase of brain-derived neurotrophic factor mRNA levels in the rat prefrontal cortex, which led us to hypothesize that ibogaine may elicit antidepressant-like effects in rats. Accordingly, we characterized behavioral effects (dose- and time-dependence) induced by the acute ibogaine and noribogaine administration in rats using the forced swim test (FST, 20 and 40 mg/kg i.p., single injection for each dose). We also examined the correlation between plasma and brain concentrations of ibogaine and noribogaine and the elicited behavioral response. We found that ibogaine and noribogaine induced a dose- and time-dependent antidepressant-like effect without significant changes of animal locomotor activity. Noribogaine’s FST effect was short-lived (30 min) and correlated with high brain concentrations (estimated >8 μM of free drug), while the ibogaine’s antidepressant-like effect was significant at 3 h. At this time point, both ibogaine and noribogaine were present in rat brain at concentrations that cannot produce the same behavioral outcome on their own (ibogaine ∼0.5 μM, noribogaine ∼2.5 μM). Our data suggests a polypharmacological mechanism underpinning the antidepressant-like effects of ibogaine and noribogaine.
Rodríguez, P., Urbanavicius, J., Prieto, J. P., Fabius, S., Reyes, A. L., Havel, V., … & Carrera, I. (2020). A Single Administration of the Atypical Psychedelic Ibogaine or its Metabolite Noribogaine Induces an Antidepressant-like Effect in Rats. ACS Chemical Neuroscience., https://doi.org/10.1021/acschemneuro.0c00152
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Dynamic coupling of whole-brain neuronal and neurotransmitter systems

Abstract

Remarkable progress has come from whole-brain models linking anatomy and function. Paradoxically, it is not clear how a neuronal dynamical system running in the fixed human anatomical connectome can give rise to the rich changes in the functional repertoire associated with human brain function, which is impossible to explain through long-term plasticity. Neuromodulation evolved to allow for such flexibility by dynamically updating the effectivity of the fixed anatomical connectivity. Here, we introduce a theoretical framework modeling the dynamical mutual coupling between the neuronal and neurotransmitter systems. We demonstrate that this framework is crucial to advance our understanding of whole-brain dynamics by bidirectional coupling of the two systems through combining multimodal neuroimaging data (diffusion magnetic resonance imaging [dMRI], functional magnetic resonance imaging [fMRI], and positron electron tomography [PET]) to explain the functional effects of specific serotoninergic receptor (5-HT2AR) stimulation with psilocybin in healthy humans. This advance provides an understanding of why psilocybin is showing considerable promise as a therapeutic intervention for neuropsychiatric disorders including depression, anxiety, and addiction. Overall, these insights demonstrate that the whole-brain mutual coupling between the neuronal and the neurotransmission systems is essential for understanding the remarkable flexibility of human brain function despite having to rely on fixed anatomical connectivity.

 
Kringelbach, M. L., Cruzat, J., Cabral, J., Knudsen, G. M., Carhart-Harris, R., Whybrow, P. C., … & Deco, G. (2020). Dynamic coupling of whole-brain neuronal and neurotransmitter systems. Proceedings of the National Academy of Sciences117(17), 9566-9576., https://doi.org/10.1073/pnas.1921475117
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Registered Clinical Trials Investigating Ketamine for Psychiatric Disorders

Abstract

As interest has grown in the potential psychiatric applications of ketamine, the number of registered clinical trials has grown substantially. Herein, we summarize and analyze clinical trials registered with ClinicalTrials.gov that assess the treatment of any psychiatric disorder with ketamine or ketamine enantiomers (e.g., S-ketamine, R-ketamine), with a focus on ongoing clinical trials. A ClinicalTrials.gov search on February 21, 2020 returned 140 registered trials. Frequency data was analyzed to determine the distribution of study designs. The majority of trials (70%) investigated the therapeutic effect of ketamine in mood disorders (unipolar: 60%, bipolar: 0.7%, both: 5.7%). Suicidal ideation (13.1%), post-traumatic stress disorder (5.4%), and obsessive-compulsive disorder (3.6%) were also investigated. Intravenous (IV) administration was the most common route with 87% of the studies using IV ketamine. Single-dose studies represented 50% of IV ketamine studies. Few studies were assessing maintenance treatment. Most studies were phase I or II with few definitive phase III trials registered. Given the large number of ongoing studies assessing psychiatric application of ketamine, researchers and relevant stakeholders should consider not only completed, published studies, but also ongoing registered studies in adjudicating the most relevant research questions. More definitive phase III trials and maintenance studies of IV ketamine for mood disorders are required, as numerous completed and ongoing studies have already assessed and demonstrated the proof-of-concept of acute antidepressant effects in phase I and II trials.
Peyrovian, B., McIntyre, R., Phan, L., Lui, L. M., Gill, H., Majeed, A., … & Rosenblat, J. D. (2020). Registered clinical trials investigating ketamine for psychiatric disorders. Journal of Psychiatric Research., https://doi.org/10.1016/j.jpsychires.2020.03.020
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Exposure-Response Analysis to Assess the Concentration-QTc Relationship of Psilocybin/Psilocin

Abstract

Psilocybin is being developed for treating major depressive disorder. Psilocybin is readily dephosphorylated to psilocin upon absorption. The potential for psilocin proarrhythmic effect was assessed using a concentration-QTc interval (C-QTc) analysis from an open-label single ascending dose study of psilocybin. Psilocybin doses ranged from 0.3 to 0.6 mg/kg. This trial showed a significant but shallow C-QTc relationship. At the clinical dose of 25 mg, the mean psilocin maximum concentration is 18.7 ng/mL, and the associated mean (upper 90% confidence interval of mean) QTcF change is 2.1 (6.6) milliseconds. Given the short half-life of psilocin of about 4 hours, there would be no accumulation after monthly oral doses used in clinical trials. The upper limit of the 90% confidence interval of the model-predicted mean ΔQTcF crossed 10 milliseconds at a psilocin concentration of 31.1 ng/mL. At a supraclinical psilocin maximum concentration of about 60 ng/mL, ΔQTcF remains low, with a mean (upper limit of the 90% confidence interval) of 9.1 (17.9) milliseconds. This analysis enabled the characterization of the C-QTc relationship and prediction of QTc prolongation at the expected clinical and possible higher psilocybin doses.

Dahmane, E., Hutson, P. R., & Gobburu, J. V. (2020). Exposure‐Response Analysis to Assess the Concentration‐QTc Relationship of Psilocybin/Psilocin. Clinical Pharmacology in Drug Development.; 10.1002/cpdd.796

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Psychedelic Psychiatry’s Brave New World

Abstract

After a legally mandated, decades-long global arrest of research on psychedelic drugs, investigation of psychedelics in the context of psychiatric disorders is yielding exciting results. Outcomes of neuroscience and clinical research into 5-Hydroxytryptamine 2A (5-HT2A) receptor agonists, such as psilocybin, show promise for addressing a range of serious disorders, including depression and addiction.

Nutt, D., Erritzoe, D., & Carhart-Harris, R. (2020). Psychedelic Psychiatry’s Brave New World. Cell181(1), 24-28.
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