Pain response to cannabidiol in opioid-induced hyperalgesia, acute nociceptive pain, and allodynia using a model mimicking acute pain in healthy adults in a randomized trial (CANAB II)

Cannabidiol interactions with oxycodone analgesia in an operant orofacial cutaneous thermal pain assay following oral administration in rats

Previous studies have driven the notion that the cannabis constituent cannabidiol could be an effective adjunct to opioid administration for managing pain. Most of these studies have used experimental rodents with routes of administration, such as subcutaneous and intraperitoneal, that do not correspond with the routes used in clinical practice. In response to this, we tested the ability of cannabidiol co-administration to augment opioid analgesia via the more clinically-relevant oral route of administration. To this end, male and female rats were orally gavaged with cannabidiol (25 mg/kg), oxycodone (1.4 mg/kg), or a combination of both, after which they were tested in an operant thermal orofacial pain assay in which they voluntarily exposed their faces to cutaneous thermal pain to receive a palatable reward. All three drug conditions produced analgesic effects of varying degrees, being most profound in the combination group where a statistically significant enhancement over oxycodone-induced analgesia alone was evident. Additionally, oxycodone administration decreased lick frequencies - a measure of motor coordination of rhythmic movements - which too was magnified by co-administration of cannabidiol. Together these studies provide further support of an ability of cannabidiol to augment opioid effects, particularly analgesia, when administered by a route relevant to human pain management. As such, they encourage the notion that cannabidiol could find utility as an opioid-sparing approach to treating pain.

Preferential C-nociceptor stimulation facilitates peripheral axon reflex flare, but not secondary mechanical hyperalgesia

"Silent" C-nociceptors are crucial for inducing the axon reflex erythema in humans and may also contribute to spinal sensitization such as secondary hyperalgesia. Electrical slow depolarizing stimulation paradigms activate unmyelinated C-fibers [25 ms half-sine (HS) profile] whereas A-fibers are stimulated by 500 µs rectangular (R) pulses. We therefore expect to provoke larger areas of axon-reflex flare (silent nociceptor activation) and secondary hyperalgesia to HS stimuli. We compared axon-reflex erythema and secondary mechanical hyperalgesia areas induced by intracutaneous electrical HS and R stimuli using stimulation intensities that induced pain ratings of 3 and 6 on a numeric rating scale (NRS 0-10) in 24 healthy volunteers. Slowly depolarizing C-fiber stimulation was linked to lower current intensities required to induce pain (NRS 6: HS 3.6 vs. R 9.2 mA, p = 0.001) and resulted in larger axon reflex erythema for high stimulus intensities (AUCFlare: NRS 6, 320.7 vs. 234.1 cm2⋅min, p = 0.015; NRS 3, 79.1 vs. 51.0 cm2⋅min; p = 0.114). Preferential C-fiber stimulation indicated a correlation of axon-reflex erythema with the areas of secondary mechanical hyperalgesia (NRS 6: r = 0.21, p = 0.036; NRS 3: r = 0.48, p = 0.0016). In contrast, the mean area of secondary mechanical hyperalgesia did not differ between HS and R [AUCHyper: NRS 6, 1,555 (HS) vs. 1,585 cm2⋅min (R), p = 0.893; NRS 3, 590 (HS) vs. 449 cm2⋅min (R), p = 0.212] albeit it developed faster during HS. Our data confirm that silent nociceptors provoke the axon reflex erythema, but their role in secondary hyperalgesia appears to be less crucial. Clinical trial number: NCT0544026.

Cannabidiol restores hematopoietic stem cell stemness in mouse through Atf2-Lrp6 axis after acute irradiation

Bone marrow serves as the residence of hematopoietic stem cells and is recognized as one of the most radiosensitive tissues. Exposure to acute radiation leads to severe damage to bone marrow hematopoiesis which can be fatal, while few clinically applicable medication or specific therapeutic targets have been discovered. In this study, we found that the administration of cannabidiol significantly enhanced individual survival and restored the reconstitution capacity of bone marrow hematopoietic stem cells within 14 days after irradiation. Single-cell RNA sequencing analysis demonstrated that the expression levels of genes associated with stemness along with Wnt and BMP signaling pathways were restored by the cannabidiol treatment through the upregulation of Atf2, a transcription factor possessing multifunctional properties. Atf2 upregulation induced by cannabidiol treatment potentially upregulated the expression of Lrp6 to improve the stemness of hematopoietic stem cells. Further functional experiments validated the crucial role of Atf2 in regulating multilineage differentiation potential of bone marrow hematopoietic stem and progenitor cells. Overall, our findings provide evidence for a promising radioprotective function of cannabidiol and Atf2 as a candidate therapeutic target for acute radiation-induced hematopoietic injury, thereby paving the way for future research in the field.

Pharmacodynamic effects following co-administration of cannabinoids and opioids: a scoping review of human experimental studies

BACKGROUND

Cannabinoids are increasingly used in the management of chronic pain. Although analgesic potential has been demonstrated, cannabinoids interact with a range of bodily functions that are also influenced by chronic pain medications, including opioids.

OBJECTIVE

We performed a scoping review of literature on the pharmacodynamic effects following the co-administration of cannabinoids and opioids.

METHODS

We systematically searched EMBASE, PubMed, and PsycINFO for studies that experimentally investigated the co-effects of cannabinoids and opioids in human subjects. Available evidence was summarized by clinical population and organ system. A risk of bias assessment was performed.

RESULTS

A total of 16 studies met the inclusion criteria. Study populations included patients with chronic non-cancer and cancer pain on long-term opioid regimens and healthy young adults without prior exposure to opioids who were subject to experimental nociceptive stimuli. Commonly administered cannabinoid agents included Δ9-tetrahydrocannabinol and/or cannabidiol. Co-administration of cannabinoids and opioids did not consistently improve pain outcomes; however, sleep and mood benefits were observed in chronic pain patients. Increased somnolence, memory and attention impairment, dizziness, gait disturbance, and nauseousness and vomiting were noted with co-administration of cannabinoids and opioids. Cardiorespiratory effects following co-administration appeared to vary according to duration of exposure, population type, and prior exposure to cannabinoids and opioids.

CONCLUSIONS

The available evidence directly investigating the pharmacodynamic effects following co-administration of cannabinoids and opioids for non-analgesic outcomes is scarce and suffers from a lack of methodological reporting. As such, further research in this area with comprehensive methodologic reporting is warranted.

Cannabinoids for Acute Pain Management: Approaches and Rationale

PURPOSE OF THE REVIEW

Acute pain management remains a challenge and postoperative pain is often undermanaged despite many available treatment options, also including cannabinoids.

RECENT FINDINGS

In the light of the opioid epidemic, there has been growing interest in alternative care bundles for pain management, including cannabinoids as potential treatment to decrease opioid prescribing. Despite the lack of solid evidence on the efficacy of cannabinoids, their use among patients with pain, including those using opioids, is currently increasing. This use is supported by data suggesting that cannabinoids could potentially contribute to a better pain management and to a reduction in opioid doses while maintaining effective analgesia with minimum side effects. The scientific basis for supporting the use of cannabis is extensive, although it does not necessarily translate into relevant clinical outcomes. The use of cannabinoids in acute pain did not always consistently show statistically significant results in improving acute pain. Large randomized, controlled trials evaluating diverse cannabis extracts are needed in different clinical pain populations to determine safety and efficacy.

Cannabidiol (CBD) Products for Pain: Ineffective, Expensive, and With Potential Harms

Cannabidiol (CBD) attracts considerable attention for promoting good health and treating various conditions, predominantly pain, often in breach of advertising rules. Examination of available CBD products in North America and Europe demonstrates that CBD content can vary from none to much more than advertised and that potentially harmful other chemicals are often included. Serious harm is associated with chemicals found in CBD products and reported in children, adults, and the elderly. A 2021 International Association for the Study of Pain task force examined the evidence for cannabinoids and pain but found no trials of CBD. Sixteen CBD randomized trials using pharmaceutical-supplied CBD or making preparations from such a source and with pain as an outcome have been published subsequently. The trials were conducted in 12 different pain states, using 3 oral, topical, and buccal/sublingual administration, with CBD doses between 6 and 1,600 mg, and durations of treatment between a single dose and 12 weeks. Fifteen of the 16 showed no benefit of CBD over placebo. Small clinical trials using verified CBD suggest the drug to be largely benign; while large-scale evidence of safety is lacking, there is growing evidence linking CBD to increased rates of serious adverse events and hepatotoxicity. In January 2023, the Food and Drug Administration (FDA) announced that a new regulatory pathway for CBD was needed. Consumers and health care providers should rely on evidence-based sources of information on CBD, not just advertisements. Current evidence is that CBD for pain is expensive, ineffective, and possibly harmful. PERSPECTIVE: There is no good reason for thinking that CBD relieves pain, but there are good reasons for doubting the contents of CBD products in terms of CBD content and purity.

Pain Management in Burn Patients: Pharmacologic Management of Acute and Chronic Pain

Burn-related pain can contribute to decreased quality of life and long-term morbidity, limiting functional recovery. Burn-related pain should be assessed first by chronicity (acute or chronic), followed by type (nociceptive, neuropathic, nociplastic), to guide multimodal pharmacologic management in a stepwise algorithm approach. Combination therapies increase the efficacy and reduce toxicity by offering a multimodal approach that targets different receptors in the peripheral nervous system and central nervous system. When multimodal pharmacologic management is ineffective, etiologies of burn-related pain amenable to surgical interventions must be considered. It is important to know when to refer a patient to pain management.

Cannabidiol and Tetrahydrocannabinol Antinociceptive Activity is Mediated by Distinct Receptors in Caenorhabditis elegans

Cannabis has gained popularity in recent years as a substitute treatment for pain following the risks of typical treatments uncovered by the opioid crisis. The active ingredients frequently associated with pain-relieving effects are the phytocannabinoids Δ9-tetrahydrocannabinol (THC) and cannabidiol (CBD), but their effectiveness and mechanisms of action are still under research. In this study, we used Caenorhabditis elegans, an ideal model organism for the study of nociception that expresses mammal ortholog cannabinoid (NPR-19 and NPR-32) and vanilloid (OSM-9 and OCR-2) receptors. Here, we evaluated the antinociceptive activity of THC and CBD, identifying receptor targets and several metabolic pathways activated following exposure to these molecules. The thermal avoidance index was used to phenotype each tested C. elegans experimental group. The data revealed for the first time that THC and CBD decreases the nocifensive response of C. elegans to noxious heat (32-35 °C). The effect was reversed 6 h post- CBD exposure but not for THC. Further investigations using specific mutants revealed CBD and THC are targeting different systems, namely the vanilloid and cannabinoid systems, respectively. Proteomic analysis revealed differences following Reactome pathways and gene ontology biological process database enrichment analyses between CBD or THC-treated nematodes and provided insights into potential targets for future drug development.

Assessing Dose- and Sex-Dependent Antinociceptive Effects of Cannabidiol and Amitriptyline, Alone and in Combination, and Exploring Mechanism of Action Involving Serotonin 1A Receptors

Inflammatory pain is caused by tissue hypersensitization and is a component of rheumatic diseases, frequently causing chronic pain. Current guidelines use a multimodal approach to pain and sociocultural changes have renewed interest in cannabinoid use, particularly cannabidiol (CBD), for pain. The tricyclic antidepressant amitriptyline (AT) is approved for use in pain-related syndromes, alone and within a multimodal approach. Therefore, we investigated sex- and dose-dependent effects of CBD and AT antinociception in the 2.5% formalin inflammatory pain model. Male and female C57BL/6J mice were pretreated with either vehicle, CBD (0.3-100 mg/kg), or AT (0.1-30 mg/kg) prior to formalin testing. In the acute phase, CBD induced antinociception after administration of 30-100 mg/kg in males and 100 mg/kg in females and in the inflammatory phase at doses of 2.5-100 mg/kg in males and 10-100 mg/kg in females. In the acute phase, AT induced antinociception at 10 mg/kg for all mice, and at 0.3 mg/kg in males and 3 mg/kg in female mice in the inflammatory phase. Combining the calculated median effective doses of CBD and AT produced additive effects for all mice in the acute phase and for males only in the inflammatory phase. Use of selective serotonin 1A receptor antagonist N-[2-[4-(2-methoxyphenyl)-1 piperazinyl]ethyl]-N-2-pyridinylcyclohexanecarboxamide (WAY-100635) maleate (0.1 mg/kg) before co-administration of CBD and AT reversed antinociception in the acute and partially reversed antinociception in the inflammatory phase. Administration of AT was found to enhance cannabinoid receptor type 1mRNA expression only in female mice. These results suggest a role for serotonin and sex in mediating cannabidiol and amitriptyline-induced antinociception in inflammatory pain. SIGNIFICANCE STATEMENT: Inflammatory pain is an important component of both acute and chronic pain. We have found that cannabidiol (CBD) and amitriptyline (AT) show dose-dependent, and that AT additionally shows sex-dependent, antinociceptive effects in an inflammatory pain model. Additionally, the combination of CBD and AT was found to have enhanced antinociceptive effects that is partially reliant of serotonin 1A receptors and supports the use of CBD within a multimodal approach to pain.

An Overview of Cannabidiol

Cannabidiol (CBD) is one of the most interesting constituents of cannabis, garnering significant attention in the medical community in recent years due to its proven benefit for reducing refractory seizures in pediatric patients. Recent legislative changes in the United States have made CBD readily available to the general public, with up to 14% of adults in the United States having tried it in 2019. CBD is used to manage a myriad of symptoms, including anxiety, pain, and sleep disturbances, although rigorous evidence for these indications is lacking. A significant advantage of CBD over the other more well-known cannabinoid delta-9-tetrahydroncannabinol (THC) is that CBD does not produce a "high." As patients increasingly self-report its use to manage their medical conditions, and as the opioid epidemic continues to drive the quest for alternative pain management approaches, the aims of this narrative review are to provide a broad overview of the discovery, pharmacology, and molecular targets of CBD, its purported and approved neurologic indications, evidence for its analgesic potential, regulatory implications for patients and providers, and future research needs.

A Comprehensive Review on the Regulatory Action of TRP Channels: A Potential Therapeutic Target for Nociceptive Pain

The transient receptor potential (TRP) superfamily of ion channels in humans comprises voltage-gated, non-selective cation channels expressed both in excitable as well as non-excitable cells. Four TRP channel subunits associate to create functional homo- or heterotetramers that allow the influx of calcium, sodium, and/or potassium. These channels are highly abundant in the brain and kidney and are important mediators of diverse biological functions including thermosensation, vascular tone, flow sensing in the kidney and irritant stimuli sensing. Inherited or acquired dysfunction of TRP channels influences cellular functions and signaling pathways resulting in multifaceted disorders affecting skeletal, renal, cardiovascular, and nervous systems. Studies have demonstrated the involvement of these channels in the generation and transduction of pain. Based on the multifaceted role orchestrated by these TRP channels, modulation of the activity of these channels presents an important strategy to influence cellular function by regulating intracellular calcium levels as well as membrane excitability. Therefore, there has been a remarkable pharmaceutical inclination toward TRP channels as therapeutic interventions. Several candidate drugs influencing the activity of these channels are already in the clinical trials pipeline. The present review encompasses the current understanding of TRP channels and TRP modulators in pain and pain management.

Oral cannabidiol (CBD) as add-on to paracetamol for painful chronic osteoarthritis of the knee: a randomized, double-blind, placebo-controlled clinical trial

Background

Painful knee osteoarthritis (KOA) is common, pharmacological treatment, however, is often hampered by limited tolerability. Cannabidiol, which preclinically showed anti-inflammatory, analgesic activity, could supplement established analgesics, but robust clinical trials are lacking. The aim of our study was to investigate the effects of oral high-dose CBD administered over 8 weeks on pain, function and patient global assessment as an add-on to continued paracetamol in chronic symptomatic KOA.

Methods

Prospective, randomized, placebo-controlled, double-blind, parallel-group study. Single center, Outpatient Clinic, Department of Special Anaesthesia and Pain Therapy at Medical University of Vienna, Austria. Eligibility criteria included: age: 18-98 years; painful KOA; score ≥5 on the pain subscale of the Western Ontario and McMasters Universities Osteoarthritis (WOMAC) Index; KOA confirmed by imaging. Participants were on continued dosage of paracetamol 3 g/d and randomly assigned by web-based software 1:1 to oral cannabidiol 600 mg/d (n = 43) or placebo (n = 43). Study period: 8 weeks. Primary outcome: Change in WOMAC pain subscale scores (0 = no pain, 10 = worst possible pain) from baseline to week 8 of treatment. Trial Registration: ClinicalTrials.gov Identifier: NCT04607603. Trial is completed.

Findings

The trial was conducted from October 1, 2020 to March 29, 2022. 159 patients screened, 86 randomized. Among 86 participants (mean age, 62.8 [SD 20.3] years; 60 females [69.8%]), 58 (67.4%) completed the trial. Mean baseline WOMAC pain subscale was 6.0 ± 1.1. Analysis: Intention-to-treat principal. Mean reduction in WOMAC pain subscale was 2.5 (95% CI: 1.8-3.3) in the cannabidiol group and 2.4 (95% CI: 1.7-3.2) in the placebo group with no significant group difference (p = 0.80). Adverse events were significantly more frequent with cannabidiol (cannabidiol: 135 [56%]; placebo: 105 [44%]) (p = 0.008). Rise above baseline of liver aminotransferases and gamma-glutamyltransferase was significantly more common in the cannabidiol (n = 15) than the placebo group (n = 5) (p = 0.02).

Interpretation

In KOA patients, oral high-dose add-on cannabidiol had no additional analgesic effect compared to adding placebo to continued paracetamol. Our results do not support the use of cannabidiol as an analgesic supplement in KOA.

Funding

Trigal Pharma GmbH.

Developmental outcomes with perinatal exposure (DOPE) to prescription opioids

Researchers have found considerable evidence in the past 20 years that perinatal opioid exposure leads to an increased risk of developmental disorders in offspring that persist into adulthood. The use of opioids to treat pain concerning pregnancy, delivery, and postpartum complications has been rising. As a result, communities have reported a 300-400 % increase in Neonatal Opioid Withdrawal Syndrome (NOWS). NOWS represents the initial stage of several behavioral, phenotypic, and synaptic deficits. This review article summarizes the Developmental Outcomes of Perinatal Exposure (DOPE) to prescription opioids. Moreover, we also seek to connect these findings to clinical research that describes DOPE at multiple stages of life. Since specific mechanisms that underlie DOPE remain unclear, this article aims to provide a framework for conceptualizing across all ages and highlight the implications they may have for longevity.

Developing non-opioid therapeutics to alleviate pain among persons with opioid use disorder: a review of the human evidence

The opioid crisis remains a major public health concern, causing significant morbidity and mortality worldwide. Pain is frequently observed among individuals with opioid use disorder (OUD), and the current opioid agonist therapies (OAT) have limited efficacy in addressing the pain needs of this population. We reviewed the most promising non-opioid analgesic therapies for opioid-dependent individuals synthesising data from randomised controlled trials in the Medline database from December 2022 to March 2023. Ketamine, gabapentin, serotoninergic antidepressants, and GABAergic drugs were found to be the most extensively studied non-opioid analgesics with positive results. Additionally, we explored the potential of cannabinoids, glial activation inhibitors, psychedelics, cholecystokinin antagonists, alpha-2 adrenergic agonists, and cholinergic drugs. Methodological improvements are required to advance the development of novel analgesic strategies and establish their safety profile for opioid-dependent populations. We highlight the need for greater integration of experimental pain methods and abuse liability assessments, more granular assessments of prior opioid exposure, greater uniformity of pain types within study samples, and a particular focus on individuals with OUD receiving OAT. Finally, future research should investigate pharmacokinetic interactions between OAT and various non-opioid analgesics and perform reverse translation basic experiments, particularly with methadone and buprenorphine, which remain the standard OUD treatment.

Cannabidiol for the Treatment of Brain Disorders: Therapeutic Potential and Routes of Administration

The use of cannabidiol (CBD) for treating brain disorders has gained increasing interest. While the mechanism of action of CBD in these conditions is still under investigation, CBD has been shown to affect numerous different drug targets in the brain that are involved in brain disorders. Here we review the preclinical and clinical evidence on the potential therapeutic use of CBD in treating various brain disorders. Moreover, we also examine various drug delivery approaches that have been applied to CBD. Due to the slow absorption and low bioavailability with the current oral CBD therapy, more efficient routes of administration to bypass hepatic metabolism, particularly pulmonary delivery, should be considered. Comparison of pharmacokinetic studies of different delivery routes highlight the advantages of intranasal and inhalation drug delivery over other routes of administration (oral, injection, sublingual, buccal, and transdermal) for treating brain disorders. These two routes of delivery, being non-invasive and able to achieve fast absorption and increase bioavailability, are attracting increasing interest for CBD applications, with more research and development expected in the near future.

Medicinal cannabis products for the treatment of acute pain

For thousands of years, medicinal cannabis has been used for pain treatment, but its use for pain management is still controversial. Meta-analysis of the literature has shown contrasting results on the addition of cannabinoids to opioids compared with placebo/other active agents to reduce pain. Clinical studies are mainly focused on medicinal cannabis use in chronic pain management, for which the analgesic effect has been proven in many studies. This review focuses on the potential use of medical cannabis for acute pain management in preclinical studies, studies on healthy subjects and the few pioneering studies in the clinical setting.