Pharmacokinetics, metabolism and drug-abuse potential of nabilone

The State of Synthetic Cannabinoid Medications for the Treatment of Pain

Synthetic cannabinoids are compounds made in the laboratory to structurally and functionally mimic phytocannabinoids from the Cannabis sativa L. plant, including delta-9-tetrahydrocannabinol (THC). Synthetic cannabinoids (SCs) can signal via the classical endogenous cannabinoid system (ECS) and the greater endocannabidiome network, highlighting their signalling complexity and far-reaching effects. Dronabinol and nabilone, which mimic THC signalling, have been approved by the Food and Drug Administration (FDA) for treating nausea associated with cancer chemotherapy and/or acquired immunodeficiency syndrome (AIDS). However, there is ongoing interest in these two drugs as potential analgesics for a variety of other clinical conditions, including neuropathic pain, spasticity-related pain, and nociplastic pain syndromes including fibromyalgia, osteoarthritis, and postoperative pain, among others. In this review, we highlight the signalling mechanisms of FDA-approved synthetic cannabinoids, discuss key clinical trials that investigate their analgesic potential, and illustrate challenges faced when bringing synthetic cannabinoids to the clinic.

Metabolic, toxicological, chemical, and commercial perspectives on esterification of dietary polyphenols: a review

Molecular modifications have been practiced for more than a century and nowadays they are widely applied in food, pharmaceutical, or other industries to manipulate the physicochemical, bioactivity, metabolic/catabolic, and pharmacokinetic properties. Among various structural modifications, the esterification/O-acylation has been well-established in altering lipophilicity and bioactivity of parent bioactive compounds, especially natural polyphenolics, while maintaining their high biocompatibility. Meanwhile, various classic chemical and enzymatic protocols and other recently emerged cell factory technology are being employed as viable esterification strategies. In this contribution, the main motivations of phenolic esterification, including the tendency to replace synthetic alkyl phenolics with safer alternatives in the food industry to improve the bioavailability of phenolics as dietary supplements/pharmaceuticals, are discussed. In addition, the toxicity, metabolism, and commercial application of synthetic and natural phenolics are briefly introduced. Under these contexts, the mechanisms and reaction features of several most prevalent chemical and enzymatic esterification pathways are demonstrated. In addition, insights into the studies of esterification modification of natural phenolic compounds and specific pros/cons of various reaction systems with regard to their practical application are provided.

Long-term safety and efficacy of open-label nabilone on sleep and pain in Parkinson´s Disease

The synthetic tetrahydrocannabinol-analog nabilone improved non-motor symptoms (NMS) in Parkinson's disease (PD) patients in a placebo-controlled, double-blind, parallel-group, randomized withdrawal trial with enriched enrollment (NMS-Nab-study). This was a single-center open-label extension study to assess the long-term safety and efficacy of nabilone for NMS in PD. To be eligible for this study, patients had to be treatment responders during the previous NMS-Nab-trial and complete its double-blind phase without experiencing a drug-related serious/severe/moderate adverse event (AE). Patients were re-introduced to nabilone during an up-titration phase until their overall NMS burden improved. Nabilone was continued for six months with clinic visits every 3 months. Evaluation of AEs was based on self-report and clinical assessment. Twenty-two patients participated in the NMS-Nab2-study (age-median 68.33 y, 52% females, disease duration-median 7.42 y). Nabilone was well tolerated with concentration difficulties as the most common treatment-related AE (possibly/not related n = 1 each). One in two drop-outs discontinued because of an AE for which a prohibited concomitant medication needed to be introduced (night-time sleep problems). Efficacy evaluation showed a significant and lasting improvement in NMS burden according to the CGI-I (79% at V3). Nabilone improved overall sleep (NMSS Domain-2: -8.26 points; 95%CI -13.82 to -2.71; p = 0.004; ES = -0.72), night-time sleep problems (MDS-UPDRS-1.7: -1.42 points; 95 CI -2.16 to -0.68; p = 0.002; ES = -0.92), and overall pain (KPPS Total Score: -8.00 points; 95%CI -15.05 to -0.95; p = 0.046; ES -0.55 and MDS-UPDRS-1.9: -0.74 points; 95%CI -1.21 to -0.26; p = 0.008; ES = -0.74). This study demonstrates continuous long-term safety and efficacy in PD patients responding early to nabilone without intolerable side effects.

Toxicological properties of Δ9-tetrahydrocannabinol and cannabidiol

Cannabis sativa L. contains more than 100 phytocannabinoids that can interact with cannabinoid receptors CB1 and CB2. None of the cannabinoid receptor ligands is entirely CB1- or CB2-specific. The effects of cannabinoids therefore differ not just because of different potency at cannabinoid receptors but also because they can interact with other non-CB1 and non-CB2 targets, such as TRPV1, GPR55, and GPR119. The most studied phytocannabinoid is Δ9-tetrahydrocannabinol (THC). THC is a partial agonist at both cannabinoid receptors, but its psychotomimetic effect is produced primarily via activation of the CB1 receptor, which is strongly expressed in the central nervous system, with the noteworthy exception of the brain stem. Although acute cognitive and other effects of THC are well known, the risk of irreversible neuropsychological effects of THC needs further research to elucidate the association. Unlike THC, phytocannabinoid cannabidiol (CBD) does not appear to have psychotomimetic effects but may interact with some of the effects of THC if taken concomitantly. CBD administered orally has recently undergone well-controlled clinical trials to assess its safety in the treatment of paediatric epilepsy syndromes. Their findings point to increased transaminase levels as a safety issue that calls for postmarketing surveillance for liver toxicity. The aim of this review is to summarise what is known about acute and chronic toxicological effects of both compounds and address the gaps in knowledge about the safety of exogenous cannabinoids that are still open.

Cannabinoid Signalling in Immune-Reproductive Crosstalk during Human Pregnancy

Despite the intricate involvement of the endocannabinoid system in various physiological processes, it remains one of the most under-studied biological systems of the human body. The scope of endocannabinoid signalling is widespread, ranging from modulation of immune responses in innate and adaptive immunity to gestational processes in female physiology. Cannabinoid receptors are ubiquitously distributed in reproductive tissues and are thought to play a role in regulating the immune-reproductive interactions required for successful pregnancy, specifically among uterine natural killer cells and placental extravillous trophoblasts. The use of cannabis during pregnancy, however, can perturb endocannabinoid homeostasis through effects mediated by its major constituents, Δ-9-tetrahydrocannabinol and cannabidiol. Decidualization of the endometrium, invasion, and angiogenesis may be impaired as a consequence, leading to clinical complications such as miscarriage and preeclampsia. In this review, the crosstalk between endocannabinoid signalling in uterine natural killer cells and placental extravillous trophoblasts will be examined in healthy and complicated pregnancies. This lays a foundation for discussing the potential of targeting the endocannabinoid system for therapeutic benefit, particularly with regard to the emerging field of synthetic cannabinoids.

Non-Motor Symptoms in Parkinson's Disease are Reduced by Nabilone

OBJECTIVE

The objective of this study was to assess the efficacy and safety of nabilone, a synthetic tetrahydrocannabinol analogue, as a treatment for non-motor symptoms (NMS) in Parkinson's disease (PD).

METHODS

This was a phase II placebo-controlled, double-blind, parallel-group, enriched enrollment randomized withdrawal trial conducted at the Medical University Innsbruck. A random sample of 47 patients with PD with stable motor disease and disturbing NMS defined by a score of ≥4 points on the Movement Disorder Society - Unified PD Rating Scale-I (MDS-UPDRS-I) underwent open-label nabilone titration (0.25 mg once daily to 1 mg twice daily, phase I). Responders were randomized 1:1 to continue with nabilone or switch to placebo for 4 weeks (phase II). The primary efficacy criterion was the change of the MDS-UPDRS-I between randomization and week 4. Safety was analyzed in all patients who received at least one nabilone dose.

RESULTS

Between October 2017 and July 2019, 19 patients received either nabilone (median dose = 0.75 mg) or placebo. At week 4, mean change of the MDS-UPDRS-I was 2.63 (95% confidence interval [CI] 1.53 to 3.74, p = 0.002, effect size = 1.15) in the placebo versus 1.00 (95% CI -0.16 to 2.16, p = 0.280, effect size = 0.42) in the nabilone-group (difference: 1.63, 95% CI 0.09 to 3.18, p = 0.030, effect size = 0.66). Seventy-seven percent of patients had adverse events (AEs) during open-label titration, most of them were transient. In the double-blind phase, similar proportions of patients in each group had AEs (42% in the placebo group and 32% in the nabilone group). There were no serious AEs.

INTERPRETATION

Our results highlight the potential efficacy of nabilone for patients with PD with disturbing NMS, which appears to be driven by positive effects on anxious mood and night-time sleep problems.

TRIAL REGISTRY

ClinicalTrials.gov (NCT03769896) and EudraCT (2017-000192-86). ANN NEUROL 2020;88:712-722.

Targeting the Endocannabinoid CB1 Receptor to Treat Body Weight Disorders: A Preclinical and Clinical Review of the Therapeutic Potential of Past and Present CB1 Drugs

Obesity rates are increasing worldwide and there is a need for novel therapeutic treatment options. The endocannabinoid system has been linked to homeostatic processes, including metabolism, food intake, and the regulation of body weight. Rimonabant, an inverse agonist for the cannabinoid CB1 receptor, was effective at producing weight loss in obese subjects. However, due to adverse psychiatric side effects, rimonabant was removed from the market. More recently, we reported an inverse relationship between cannabis use and BMI, which has now been duplicated by several groups. As those results may appear contradictory, we review here preclinical and clinical studies that have studied the impact on body weight of various cannabinoid CB1 drugs. Notably, we will review the impact of CB1 inverse agonists, agonists, partial agonists, and neutral antagonists. Those findings clearly point out the cannabinoid CB1 as a potential effective target for the treatment of obesity. Recent preclinical studies suggest that ligands targeting the CB1 may retain the therapeutic potential of rimonabant without the negative side effect profile. Such approaches should be tested in clinical trials for validation.

Cannabinoids for the Neuropsychiatric Symptoms of Dementia: A Systematic Review and Meta-Analysis

BACKGROUND

In 2016, the global number of individuals living with dementia was 43.8 million, representing a 117% increase from 1990-mainly due to increases in aging and population growth. Up to 90% of individuals with dementia experience neuropsychiatric symptoms (NPS). However, the limitations of current treatments for NPS have drivent he search for safer pharmacotherapies-including cannabinoids.

AIM

To assess the efficacy and acceptability of cannabinoids for the treatment of NPS in individuals with dementia.

DESIGN

Systematic review and meta-analysis of clinical trials.

SETTING AND PARTICIPANTS

Of 6,902 papers, 9 were eligible (n = 205, 44% female, 78 ± 7 years, 85% Alzheimer disease). Trials were in North America and Europe and explored tetrahydrocannabinol (n = 3), dronabinol (n = 5), or nabilone (n = 1).

MEASUREMENT

Titles/abstracts were independently screened by one reviewer and reviewed by a second. Full-text screening was by two reviewers with discrepancies resolved via a third reviewer. We extracted data on the standardized mean difference (SMD) for several NPS instruments, trial completion, and adverse events. Data were pooled using random-effects models.

FINDINGS

Cannabinoids led to significant improvements across NPS instruments, including the Cohen Mansfield Agitation Inventory (SMD = -0.80; 95% confidence interval [CI], -1.45 to -0.16), the Neuropsychiatric Inventory (SMD = -0.61; CI, -1.07 to -0.15), and nocturnal actigraphy (SMD = -1.05; CI, -1.56 to -0.54h). Cannabinoids were well-tolerated, with an overall trial completion rate of 93% (193/205) and no serious treatment-related adverse events. Treatment efficacy was associated with baseline dementia severity and dose, but not dementia subtype, age, or sex. The overall study quality was rated as low.

CONCLUSIONS

There is preliminary evidence for the efficacy and tolerability of cannabinoids as treatments for NPS. Population-based studies are needed to characterize their real-world effectiveness and acceptability.

Nabilone administration in refractory chronic diarrhea: a case series

Background

Daily cannabis assumption is currently associated with several physical and mental health problems, however in the past it was prescribed for a multitude of symptoms, including vomiting, abdominal pain and diarrhea. Through the years, the endocannabinoid system has been recognized in the homeostatic mechanisms of the gut, as well as in the physiological control of intestinal motility and secretion. Accordingly, cannabinoids may be a promising therapy against several gastrointestinal conditions, such as abdominal pain and motility-related disorders.

Case presentation

We retrospectively analysed the efficacy and safety of a CB1-receptor agonist administered in six patients with refractory chronic diarrhea, between April 2008 and July 2016. After three months of therapy, oral nabilone improved the health of nearly all patients, with visible improvements in reducing diarrheal symptoms and weight gain. Most of the benefits persisted through the three-month follow-up. Only one patient interrupted the treatment after one month, due to severe fatigue and mental confusion; the symptoms disappeared in the follow-up period.

Conclusions

These findings encourage the study of cannabinoids acting on CB1 receptors in chronic gastrointestinal disorders, especially in refractory chronic diarrhea, offering a chance for a substantial improvement in the quality of life of selected patients, with a reasonable safety profile.

Pharmaceutical cannabinoid use in Manitoba, 2004/05 to 2014/15: a population-based cross-sectional study

BACKGROUND

Pharmaceutically derived cannabinoids are used for several indications, particularly pain management. The extent of their use from a population perspective is unknown; hence, the aim of this study was to evaluate trends in pharmaceutical cannabinoid use in Manitoba.

METHODS

This was a retrospective population-based cross-sectional study using administrative data from the Manitoba Centre for Health Policy. Pharmaceutical cannabinoid users residing in Manitoba from Apr. 1, 2004, to Mar. 31, 2015 were identified. We assessed the annual prevalence and incidence of pharmaceutical cannabinoid use, and the sociodemographic characteristics and medical conditions of users.

RESULTS

We identified 5181 people who received at least 1 prescription for a pharmaceutical cannabinoid over the study period, 5033 of whom received their first prescription after Apr. 1, 2004. Nabilone accounted for 73 650 (96.0%) of all prescriptions dispensed; dronabinol was discontinued during the study period. The annual prevalence rate of use increased by 527.2%, from 21.5 (95% confidence interval [CI] 21.4-21.6) users per 100 000 people in 2004/05 to 134.9 (95% CI 134.7-135.1) users per 100 000 people in 2014/15. The annual incidence rate increased by 413.3%, from 12.1 (95% CI 12.1-12.2) users per 100 000 person-years in 2004/05 to 62.2 (95% CI 62.1-62.4) users per 100 000 person-years in 2014/15. The highest use was among older adults aged 46-64 years, females and urban area residents. One-third of incident users (1775 [35.3%]) had a diagnosis of fibromyalgia in a 2-year period before their first cannabinoid prescription. General practitioners initiated almost half (2350 [46.7%]) of first prescriptions, and anesthesiologists/pain specialists initiated one-quarter (1299 [25.8%]).

INTERPRETATION

The prevalence and incidence of pharmaceutical cannabinoid use increased over time. These findings provide insight into the use of cannabinoids before the introduction of recreational marijuana, which may affect this trend.

Current evidence of cannabinoid-based analgesia obtained in preclinical and human experimental settings

Cannabinoids have a long record of recreational and medical use and become increasingly approved for pain therapy. This development is based on preclinical and human experimental research summarized in this review. Cannabinoid CB₁ receptors are widely expressed throughout the nociceptive system. Their activation by endogenous or exogenous cannabinoids modulates the release of neurotransmitters. This is reflected in antinociceptive effects of cannabinoids in preclinical models of inflammatory, cancer and neuropathic pain, and by nociceptive hypersensitivity of cannabinoid receptor-deficient mice. Cannabis-based medications available for humans mainly comprise Δ⁹ -tetrahydrocannabinol (THC), cannabidiol (CBD) and nabilone. During the last 10 years, six controlled studies assessing analgesic effects of cannabinoid-based drugs in human experimental settings were reported. An effect on nociceptive processing could be translated to the human setting in functional magnetic resonance imaging studies that pointed at a reduced connectivity within the pain matrix of the brain. However, cannabinoid-based drugs heterogeneously influenced the perception of experimentally induced pain including a reduction in only the affective but not the sensory perception of pain, only moderate analgesic effects, or occasional hyperalgesic effects. This extends to the clinical setting. While controlled studies showed a lack of robust analgesic effects, cannabis was nearly always associated with analgesia in open-label or retrospective reports, possibly indicating an effect on well-being or mood, rather than on sensory pain. Thus, while preclinical evidence supports cannabinoid-based analgesics, human evidence presently provides only reluctant support for a broad clinical use of cannabinoid-based medications in pain therapy.

SIGNIFICANCE

Cannabinoids consistently produced antinociceptive effects in preclinical models, whereas they heterogeneously influenced the perception of experimentally induced pain in humans and did not provide robust clinical analgesia, which jeopardizes the translation of preclinical research on cannabinoid-mediated antinociception into the human setting.

The endocannabinoid system as a target for addiction treatment: Trials and tribulations

Addiction remains a major public health concern, and while pharmacotherapies can be effective, clinicians are limited by the paucity of existing interventions. Endocannabinoid signaling is involved in reward and addiction, which raises the possibility that drugs targeting this system could be used to treat substance use disorders. This review discusses findings from randomized controlled trials evaluating cannabinergic medications for addiction. Current evidence suggests that pharmacotherapies containing delta-9-tetrahydrocannabinol, such as dronabinol and nabiximols, are effective for cannabis withdrawal. Dronabinol may also reduce symptoms of opioid withdrawal. The cannabinoid receptor 1 (CB1) inverse agonist rimonabant showed promising effects for smoking cessation but also caused psychiatric side effects and currently lacks regulatory approval. Few trials have investigated cannabinergic medications for alcohol use disorder. Overall, the endocannabinoid system remains a promising target for addiction treatment. Development of novel medications such as fatty acid amide hydrolase inhibitors and neutral CB1 antagonists promises to extend the range of available interventions. This article is part of the Special Issue entitled "A New Dawn in Cannabinoid Neurobiology".

Medical cannabis - the Canadian perspective

Cannabis has been widely used as a medicinal agent in Eastern medicine with earliest evidence in ancient Chinese practice dating back to 2700 BC. Over time, the use of medical cannabis has been increasingly adopted by Western medicine and is thus a rapidly emerging field that all pain physicians need to be aware of. Several randomized controlled trials have shown a significant and dose-dependent relationship between neuropathic pain relief and tetrahydrocannabinol – the principal psychoactive component of cannabis. Despite this, barriers exist to use from both the patient perspective (cost, addiction, social stigma, lack of understanding regarding safe administration) and the physician perspective (credibility, criminality, clinical evidence, patient addiction, and policy from the governing medical colleges). This review addresses these barriers and draws attention to key concerns in the Canadian medical system, providing updated treatment approaches to help clinicians work with their patients in achieving adequate pain control, reduced narcotic medication use, and enhanced quality of life. This review also includes case studies demonstrating the use of medical marijuana by patients with neuropathic low-back pain, neuropathic pain in fibromyalgia, and neuropathic pain in multiple sclerosis. While significant preclinical data have demonstrated the potential therapeutic benefits of cannabis for treating pain in osteoarthritis, rheumatoid arthritis, fibromyalgia, and cancer, further studies are needed with randomized controlled trials and larger study populations to identify the specific strains and concentrations that will work best with selected cohorts.

Effects of zolpidem alone and in combination with nabilone on cannabis withdrawal and a laboratory model of relapse in cannabis users

RATIONALE

Each year, over 300,000 individuals in the USA enter treatment for cannabis use disorder (CUD). The development of effective pharmacotherapy for CUD is a priority.

OBJECTIVE

This placebo-controlled study examined the effects of zolpidem alone and in combination with nabilone on cannabis withdrawal and a laboratory measure of relapse.

METHODS

Eleven daily, non-treatment-seeking cannabis users completed three, 8-day inpatient phases; each phase tested a different medication condition in counter-balanced order. On the first day of each phase, participants were administered placebo capsules t.i.d. and smoked experimenter-administered active cannabis (5.6 % Δ(9)-tetrahydrocannabinol (THC)). On days 2-8, the participants were administered capsules containing either placebo (0 mg at 0900, 1800, and 2300 hours), zolpidem (0 mg at 0900 and 1800, and 12.5 mg at 2300), or zolpidem (12.5 mg at 2300) and nabilone (3 mg at 0900 and 1800). Cannabis withdrawal, subjective capsule effects, and cognitive performance were examined on days 3-4, when only inactive cannabis (0.0 % THC) was available for self-administration. "Relapse" was measured on days 5-8, when participants could self-administer active cannabis.

RESULTS

Both medication conditions decreased withdrawal-related disruptions in sleep, but only zolpidem in combination with nabilone decreased withdrawal-related disruptions in mood and food intake relative to placebo. Zolpidem in combination with nabilone, but not zolpidem alone, decreased self-administration of active cannabis. Zolpidem in combination with nabilone also produced small increases in certain abuse-related subjective capsule ratings, while zolpidem alone did not. Neither medication condition altered cognitive performance.

CONCLUSIONS

Clinical testing of nabilone, either alone, or in combination with zolpidem is warranted.

Dronabinol and lofexidine for cannabis use disorder: A randomized, double-blind, placebo-controlled trial

BACKGROUND

Cannabis use disorder is associated with substantial morbidity and, after alcohol, is the most common drug bringing adolescents and adults into treatment. At present, there are no FDA-approved medications for cannabis use disorder. Combined pharmacologic interventions might be particularly useful in mitigating withdrawal symptoms and promoting abstinence.

OBJECTIVE

The purpose of this study was to evaluate the safety and efficacy of dronabinol, a synthetic form of delta-9-tetrahydrocannabinol, a naturally occurring pharmacologically active component of marijuana, and lofexidine, an alpha-2 agonist, in treating cannabis dependence.

METHODS

One hundred fifty six cannabis-dependent adults were enrolled and following a 1-week placebo lead-in phase 122 were randomized in a double-blind, placebo-controlled, 11-week trial. Participants were randomized to receive dronabinol 20mg three times a day and lofexidine 0.6 mg three times a day or placebo. Medications were maintained until the end of week eight, were then tapered over two weeks and patients were monitored off medications during the last study week. All participants received weekly motivational enhancement and relapse prevention therapy. Marijuana use was assessed using the timeline follow-back method.

RESULTS

There was no significant difference between treatment groups in the proportion of participants who achieved 3 weeks of abstinence during the maintenance phase of the trial (27.9% for the medication group and 29.5% for the placebo group), although both groups showed a reduction over time.

CONCLUSIONS

Based on this treatment study, the combined intervention did not show promise as a treatment for cannabis use disorder.

Cannabinoids in Medical Practice

Many patients with chronic medical illnesses use cannabinoids. There are two FDA-approved cannabinoid products, whereas medical marijuana purchased at legal dispensaries is not FDA regulated and may contain uncertain concentrations of various compounds. Cannabinoids have shown efficacy in treating chemotherapy-related nausea and vomiting, poor appetite in advanced HIV, some pain states, and multiple sclerosis-associated spasticity. Recreational cannabinoid use has many known potential serious harms. Physicians should be knowledgeable about cannabinoids and should inquire with their patients about cannabinoid use. Practical suggestions for clinical approaches are included.

Subjective, cognitive and cardiovascular dose-effect profile of nabilone and dronabinol in marijuana smokers

Marijuana dependence is a substantial public health problem, with existing treatments showing limited efficacy. In laboratory and clinical studies, the cannabinoid receptor 1 agonist oral Δ9tetrahydrocannabinol (THC; dronabinol) has been shown to decrease marijuana withdrawal but not relapse. Dronabinol has poor bioavailability, potentially contributing to its failure to decrease relapse. The synthetic THC analogue, nabilone, has better bioavailability than dronabinol. We therefore aimed to characterize nabilone's behavioral and physiological effects across a range of acute doses in current marijuana smokers and compare these with dronabinol's effects. Participants (4 female; 10 male) smoking marijuana 6.6 (standard deviation = 0.7) days/week completed this outpatient, within-subjects, double-blind, randomized protocol. Over seven sessions, the time-dependent subjective, cognitive and cardiovascular effects of nabilone (2, 4, 6, 8 mg), dronabinol (10, 20 mg) and placebo were assessed. Nabilone (4, 6, 8 mg) and dronabinol (10, 20 mg) increased ratings of feeling a good effect, a strong effect and/or 'high' relative to placebo; nabilone had a slower onset of peak subjective effects than dronabinol. Nabilone (6, 8 mg) modestly lowered psychomotor speed relative to placebo and dronabinol. There were dose-dependent increases in heart rate after nabilone, and nabilone (2 mg) and dronabinol (10 mg) decreased systolic blood pressure. Thus, nabilone produced sustained, dose-related increases in positive mood, few cognitive decrements and lawful cardiovascular alterations. It had a longer time to peak effects than dronabinol, and effects were more dose-related, suggesting improved bioavailability. Nabilone was well tolerated by marijuana smokers, supporting further testing as a potential medication for marijuana dependence.

Nabilone decreases marijuana withdrawal and a laboratory measure of marijuana relapse

Few individuals seeking treatment for marijuana use achieve sustained abstinence. The cannabinoid receptor agonist, Δ(9)-tetrahydrocannabinol (THC; dronabinol), decreases marijuana withdrawal symptoms, yet does not decrease marijuana use in the laboratory or clinic. Dronabinol has poor bioavailability, which may contribute to its poor efficacy. The FDA-approved synthetic analog of THC, nabilone, has higher bioavailability and clearer dose-linearity than dronabinol. This study tested whether nabilone administration would decrease marijuana withdrawal symptoms and a laboratory measure of marijuana relapse relative to placebo. Daily, nontreatment-seeking marijuana smokers (8 men and 3 women), who reported smoking 8.3±3.1 marijuana cigarettes/day completed this within-subject study comprising three, 8-day inpatient phases; each phase tested a different nabilone dose (0, 6, 8 mg/day, administered in counter-balanced order on days 2-8). On the first inpatient day, participants took placebo capsules and smoked active marijuana (5.6% THC) at six timepoints. For the next 3 days, they had the opportunity to self-administer placebo marijuana (0.0% THC; withdrawal), followed by 4 days in which active marijuana was available for self-administration (5.6% THC; relapse). Both nabilone dose conditions decreased marijuana relapse and reversed withdrawal-related irritability and disruptions in sleep and food intake (p<0.05). Nabilone (8 mg/day) modestly worsened psychomotor task performance. Neither dose condition increased ratings of capsule 'liking' or desire to take the capsules relative to placebo. Thus, nabilone maintenance produced a robust attenuation of marijuana withdrawal symptoms and a laboratory measure of relapse even with once per day dosing. These data support testing of nabilone for patients seeking marijuana treatment.

Separate and combined effects of the cannabinoid agonists nabilone and Δ⁹-THC in humans discriminating Δ⁹-THC

BACKGROUND

Agonist replacement treatment is a promising strategy to manage cannabis-use disorders. The aim of this study was to assess the combined effects of the synthetic cannabinoid agonist nabilone and Δ⁹-tetrahydrocannabinol (Δ⁹-THC) using drug-discrimination procedures, which are sensitive to drug interactions. Testing the concurrent administration of nabilone and Δ⁹-THC was also conducted to provide initial safety and tolerability data, which is important because cannabis users will likely lapse during treatment.

METHODS

Six cannabis users learned to discriminate 30 mg oral Δ⁹-THC from placebo and then received nabilone (0, 1 and 3mg) and Δ⁹-THC (0, 5, 15 and 30 mg), alone and in combination. Subjects completed the multiple-choice procedure to assess drug reinforcement, and self-report, task performance and physiological measures were collected.

RESULTS

Δ⁹-THC and nabilone alone shared discriminative-stimulus effects with the training dose of Δ⁹-THC, increased crossover point on the multiple-choice procedure, produced overlapping subject ratings and decreased skin temperature. Nabilone alone also elevated heart rate. In combination, nabilone shifted the discriminative-stimulus effects of Δ⁹-THC leftward/upward and enhanced Δ⁹-THC effects on the other outcome measures.

CONCLUSIONS

These results replicate a previous study demonstrating that nabilone shares agonist effects with the active constituent of cannabis in cannabis users, and contribute further by indicating that nabilone would likely be safe and well tolerated when combined with cannabis. These data support the conduct of future studies to determine if nabilone treatment would produce cross-tolerance to the abuse-related effects of cannabis and reduce cannabis use.

The abuse potential of the synthetic cannabinoid nabilone

AIM

Nabilone is a synthetic cannabinoid prescription drug approved in Canada since 1981 to treat chemotherapy-induced nausea and vomiting. In recent years, off-label use of nabilone for chronic pain management has increased, and physicians have begun to express concerns about nabilone becoming a drug of abuse. This study evaluates the evidence for abuse of nabilone, which is currently ill-defined.

STUDY DESIGN

Scientific literature, popular press and internet databases were searched extensively for evidence of nabilone abuse. Focused interviews with medical professionals and law enforcement agencies across Canada were also conducted.

FINDINGS

The scientific literature and popular press reviews found very little reference to nabilone abuse. Nabilone is perceived to produce more undesirable side effects, to have a longer onset of action and to be more expensive than smoked cannabis. The internet review revealed rare and isolated instances of recreational use of nabilone. The database review yielded little evidence of nabilone abuse, although nabilone seizures and thefts have occurred in Canada in the past few years, especially in Ontario. Most law enforcement officers reported no instances of nabilone abuse or diversion, and the drug has no known street value. Medical professionals reported that nabilone is not perceived to be a matter of concern with respect to its abuse potential.

CONCLUSIONS

Reports of nabilone abuse are extremely rare. However, follow-up of patients using nabilone for therapeutic purposes is prudent and should include assessment of tolerance and dependence. Prospective studies are also needed to definitively address the issue of nabilone abuse.

Cannabinoids in the management of difficult to treat pain

This article reviews recent research on cannabinoid analgesia via the endocannabinoid system and non-receptor mechanisms, as well as randomized clinical trials employing cannabinoids in pain treatment. Tetrahydrocannabinol (THC, Marinol((R))) and nabilone (Cesamet((R))) are currently approved in the United States and other countries, but not for pain indications. Other synthetic cannabinoids, such as ajulemic acid, are in development. Crude herbal cannabis remains illegal in most jurisdictions but is also under investigation. Sativex((R)), a cannabis derived oromucosal spray containing equal proportions of THC (partial CB(1) receptor agonist ) and cannabidiol (CBD, a non-euphoriant, anti-inflammatory analgesic with CB(1) receptor antagonist and endocannabinoid modulating effects) was approved in Canada in 2005 for treatment of central neuropathic pain in multiple sclerosis, and in 2007 for intractable cancer pain. Numerous randomized clinical trials have demonstrated safety and efficacy for Sativex in central and peripheral neuropathic pain, rheumatoid arthritis and cancer pain. An Investigational New Drug application to conduct advanced clinical trials for cancer pain was approved by the US FDA in January 2006. Cannabinoid analgesics have generally been well tolerated in clinical trials with acceptable adverse event profiles. Their adjunctive addition to the pharmacological armamentarium for treatment of pain shows great promise.

Experience with the Synthetic Cannabinoid Nabilone in Chronic Noncancer Pain

Chronic noncancer pain includes a heterogeneous group of disorders and is often refractory to treatment. Cannabis products have historically been used for chronic pain and are attracting renewed pharmaceutical interest. Nabilone is a synthetic cannabinoid licensed in Canada for the treatment of severe nausea and vomiting associated with cancer chemotherapy. We have used nabilone off-label for the treatment of chronic noncancer pain since 1999. In this article, we review our clinical experience of 20 adult patients with chronic noncancer pain who had been treated with nabilone and followed up for an average of 1.5 years. Prior to nabilone therapy, patients had used a wide range of therapies, including 11 who had used cannabis. Fifteen patients reported subjective overall improvement with nabilone, and nine reported reduced pain intensity. Beneficial effects on sleep and nausea were the main reasons for continuing use. Intolerable side effects were experienced in three patients (palpitations, urinary retention, dry mouth). Nabilone may be a useful addition to pain management and should be further evaluated in randomized controlled trials.

Postural syncope after marijuana: a transcranial Doppler study of the hemodynamics

Twenty-nine volunteers participated in a randomized, double-blind, placebo-controlled study. Cerebral blood velocity (CBV), pulse rate, blood pressure (BP), skin perfusion (SP) on forehead and plasma delta9 tetrahydrocannabinol (THC) levels were quantified during reclining and standing for 10 min before and after THC infusions and marijuana smoking. Both THC and marijuana induced postural dizziness, with 28% reporting severe symptoms. Intoxication and dizziness peaked immediately after drug. The severe dizziness group showed the most marked postural drop in CBV and BP and showed a drop in pulse rate after an initial increase during standing. Postural dizziness was unrelated to plasma levels of THC and other indices.

Effect of the synthetic cannabinoid nabilone on spermatogenesis in mice

Chronic treatment of mice with the synthetic cannabinoid nabilone (50 mg/kg, 3 times per week) reduced the number of pachytene spermatocytes. Nabilone did not affect other cell types in the testis or the sex organ weights. Nabilone tended to increase the number of abnormal spermatozoa, but this did not reach statistical significance. It is concluded that nabilone causes less testicular toxicity than the natural cannabinoids.

Therapeutic management of nausea and vomiting

1. The aim of this study is to review the mechanisms implicated in nausea and vomiting and the treatment of these symptoms. 2. Metoclopramide, a benzamide, is the drug most frequently used to alleviate or abolish the majority of nausea and vomiting of different origin. Domperidone, which scarcely penetrates the central nervous system (CNS), is less used. 3. The treatment of vomiting induced by cytotoxic drugs is necessary to use a combination (two or more) of antiemetic drugs (metoclopramide, glucocorticoids, antihistamines, butyrophenones, anticholinergics, cannabinoids). Recently, antagonists of serotonergic (5-HT) receptors of the subtype 5-HT3 appear to possess interesting antiemetic properties and they have a promising future in this field. 4. Antagonists of dopamine receptors (benzamides, phenotiazines, butyrophenones and domperidone) induce adverse reactions in CNS (mainly extrapyramidal disorders), which are scarce with metoclopramide and practically absent with domperidone. These disorders must not suppress antiemetic therapy when it is needed.

An EEG investigation on nabilone, a synthetic cannabinoid, in rabbits

In this paper, the electroencephalographic (EEG) and behavioural effects of nabilone, a derivative compound from delta 9-tetrahydrocannabinol (delta 9-THC), are studied in comparison with those of delta 8-tetrahydrocannabinol (delta 8-THC) in rabbits. The results show that nabilone requires lower doses than delta 8-THC to elicit cortical spike-and-wave complexes, but higher doses to disrupt hippocampal theta rhythm. These data are discussed in connection with the clinical actions of nabilone in man.

Nabilone: an alternative antiemetic for cancer chemotherapy

A prospective randomised double blind crossover trial was conducted comparing the new synthetic cannabinoid nabilone with oral domperidone in a group of children receiving repeated identical courses of emetogenic chemotherapy for a variety of malignant diseases. Eighteen of 23 consecutive eligible children, aged 10 months to 17 years, completed the trial. When taking nabilone they experienced significantly fewer vomiting episodes and less nausea, and two thirds expressed a preference for the drug. The most common side effects of treatment with nabilone were somnolence and dizziness, with one patient being disturbed by hallucinations. The results indicate that nabilone is an effective antiemetic for children having chemotherapy, even for young children. It seems to be superior in this respect to domperidone, and although it has a higher incidence of side effects, these are mostly acceptable to patients. It can be recommended as an alternative to conventional antiemetic treatment throughout childhood.

Advances in anti-emetic therapy

Evaluation of the activity of anti-emetic drugs in randomized controlled trials has, in most cases, demonstrated the superiority of treatment over placebo administration for the control of chemotherapy-induced emesis (see Table 15). The degree of control of emesis relates both to the intensity of the emetogenic stimulus and to the effectiveness of the anti-emetic agent employed. Prochlorperazine is a relatively weak anti-emetic. The drug exhibits modest activity in the treatment of emesis produced by mild emetogenic stimuli, but is relatively ineffective in the treatment of patients on moderate to severely emetogenic drugs. Domperidone has demonstrated activity against moderately emetogenic stimuli but has not been evaluated in cisplatin-treated patients. The cannabinoids have proved efficacious in the treatment of emesis induced by more severe emetogenic stimuli. THC therapy, however, has been limited in some studies by toxicity. High-dose metoclopramide has demonstrated efficacy in small series of patients in the treatment of cisplatin-induced vomiting. Dexamethasone activity as a single agent is in doubt but the drug may improve the efficacy of metoclopramide when used in combination. For the future, the use of combinations of anti-emetics with differing sites of action and non-overlapping toxicities, may lead to further improvement in efficacy. Combinations of centrally-acting drugs such as the cannabinoids plus dopamine antagonists such as metoclopramide or domperidone, are worth evaluating. The control of anticipatory nausea and vomiting is another major area of interest which has, as yet, not been studied in any depth. A single comparative trial has been reported in the literature (50) and in this study, behavioural therapy rather than drug therapy was evaluated. There may be a place for the evaluation of behavioural therapy in combination with drugs exhibiting anxiolytic properties such as the benzodiazepines and the cannabinoids. Finally, new anti-emetic drugs with an improved therapeutic index will be welcomed by the patient.