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Cannabinoids in Urology. Which Benign Conditions Might They Be Appropriate to Treat: A Systematic Review
Abstract
here is growing evidence suggesting cannabinoids may provide suitable alternatives to conventional treatments in anincreasing number of clinical settings. This review evaluates how cannabinoids are used to treat certain benign urologicalpathologies and to clarify the clinical value of this data. This review includes 62 papers and was undertaken per PRIS-MA’s guidelines, it evidences the therapeutic potential of cannabinoids in the management of specific benign urologicaldiseases, most notably neurogenic bladder dysfunction (clinical studies), renal disease (animal studies), and interstitialcystitis (animal studies). However, whilst cannabinoids are increasingly used, they cannot be considered reliable alterna-tives to more recognised treatment
... Effects mediated by cannabinoids have been studied both in isolated tissues and in experimental in vivo models of normal micturition and bladder dysfunction [83,93,94]. Anandamide is known to also activate TRPV1 receptors, potentially via the release of CGRP, which makes it difficult to evaluate its effects [95]. ...
... In a systematic review, Taylor and Birch [94] evaluated cannabinoids used to treat certain benign urological pathologies and tried to clarify the clinical value of this data. They concluded that cannabinoids have a therapeutic potential in the management of specific benign urological diseases, most notably neurogenic bladder dysfunction (clinical studies), renal disease (animal studies), and interstitial cystitis (animal studies). ...
Introduction
. Current drug treatment of lower urinary tract disorders, e.g., overactive bladder syndrome and lower urinary tract symptoms associated with benign prostatic hyperplasia, is moderately effective, has a low treatment persistence and some short- and long-term adverse events. Even if combination therapy with approved drugs may offer advantages in some patients, there is still a need for new agents.
Areas covered
New b3-adrenoceptor agonists, antimuscarinics, the naked Maxi-K channel gene, a novel 5HT/NA reuptake inhibitor and soluble guanylate cyclase activators are discussed. Focus is given to P2X3 receptor antagonists, small molecule blockers of TRP channels, the roles of cannabis on incontinence in patients with multiple sclerosis, and of drugs acting directly on CB1 and CB2 receptor or indirectly via endocannabinoids by inhibition of fatty acid aminohydrolase.
Expert opinion
New potential alternatives to currently used drugs/drug principles are emerging, but further clinical testing is required before they can be evaluated as therapeutic alternatives. It seems that for the near future individualized treatment with approved drugs and their combinations will be the prevailing therapeutic approach.
... tratamiento con gabapentinoides, antidepresivos tricíclicos e inhibidores selectivos de la recaptación de serotonina debe titularse para evitar efectos adversos intolerables, y debe individualizarse debido a las importantes diferencias interindividuales (3). Es en este contexto en el que los medicamentos a base de cannabis pueden tener su sitio para el tratamiento del dolor visceral crónico refractario (2). ...
... Se encontraron dos revisiones sistemáticas publicadas en el año 2020, una de ellas de moderada calidad (84) y una de baja calidad (108). Los resultados de la revisión de mayor calidad fueron tomados para este resumen de evidencia. ...
Este resumen de evidencia pretende sintetizar la información sobre los límites de control empleados en otras jurisdicciones, y la evidencia sobre la efectividad y seguridad de los medicamentos a base de cannabis. Aunque el énfasis de este resumen de evidencia se centra en cannabis medicinal, también consideramos información de otros productos terminados, cuando los resultados de la búsqueda presentaron evidencia al respecto.
Purpose of Review
Physical and psychological symptom burden in patients with advanced chronic kidney disease (CKD) is significantly debilitating; yet, it is often inadequately treated. Legalization of cannabis in Canada may attract increasing interest from patients for its medical use in refractory symptom management, but its indications and long-term adverse health impacts are poorly established, creating a challenge for clinicians to support its use. In this review, we summarize key clinical studies and the level of evidence for nonsynthetic cannabinoids in the treatment of common symptoms encountered in advanced stages of CKD, including chronic pain, nausea and vomiting, anorexia, pruritus, and insomnia.
Sources of Information
Medline and Embase
Methods
A search was conducted in MEDLINE and EMBASE (inception to March 1, 2018) on cannabis and CKD symptoms of interest, complemented with a manual review of bibliographies. Studies that examined synthetic cannabinoids that are manufactured to mimic the effects of ∆9-tetrahydrocannabinol such as dronabinol, levonantradol, nabilone, and ajulemic acid were excluded. We focused on studies with higher level of evidence where available, and quality of studies was graded based on the Oxford Centre for Evidence-based Medicine Levels of Evidence (1a to 5).
Findings
Based on studies conducted in patients without renal impairment, those treated with nonsynthetic cannabinoids were 43% to 300% more likely to report a ≥30% reduction in chronic neuropathic pain compared with placebo. However, there is currently insufficient evidence to recommend nonsynthetic cannabinoids for other medical indications, although preliminary investigation into topical endocannabinoids for uremia-induced pruritus in end-stage renal disease is promising. Finally, any benefits of cannabis may be offset by potential harms in the form of cognitive impairment, increased risk of mortality post-myocardial infarction, orthostatic hypotension, respiratory irritation, and malignancies (with smoked cannabis).
Limitations
Nonsynthetic cannabinoid preparations were highly variable between studies, sample sizes were small, and study durations were short. Due to an absence of studies conducted in CKD, recommendations were primarily extrapolated from the general population.
Implications
Until further studies are conducted, the role of nonsynthetic cannabinoids for symptom management in patients with CKD should be limited to the treatment of chronic neuropathic pain. Clinicians need to be cognizant that nonsynthetic cannabinoid preparations, particularly smoked cannabis, can pose significant health risks and these must be cautiously weighed against the limited substantiated therapeutic benefits of cannabis in patients with CKD.
Diabetic nephropathy (DN), a distinct manifestation of diabetic kidney disease, affects approximately 30% of patients with diabetes. While most attention has been focused on glomerular changes related to DN, there is growing evidence that tubulopathy is a key feature in the pathogenesis of this disease. The renal proximal tubule cells (RPTCs) are particularly sensitive to the deleterious effect of chronic hy-perglycemia. However, the cellular changes that control the dysfunction of the RPTCs are not fully understood. Controlling glucose reabsorption in the proximal tubules via inhibition of glucose transporters (GLUT) has emerged as a promising therapeutic in ameliorating DN. Overactivation of the renal endocannabinoid (eCB) system via the cannabinoid-1 receptor (CB 1 R) contributes to the development of DN, and its blockade by globally acting or peripherally restricted CB 1 R antagonists has been shown to ameliorate renal dys-function in different murine models for diabetes. Recently, we have utilized various pharmacological and genetic tools to show that the eCB/CB 1 R system contributes to the development of DN via regulating the expression, translocation, and activity of the facilitative GLUT2 located in the RPTCs. These findings have the potential to be translated into therapy , and support the rationale for the preclinical development of novel renal-specific CB 1 R and/or GLUT2 inhibitors for the treatment of DN.
Importance
Cannabinoids have antispastic and analgesic effects; however, their role in the treatment of multiple sclerosis (MS) symptoms is not well defined.
Objective
To conduct a systematic review and meta-analysis to assess the efficacy and tolerability of medicinal cannabinoids compared with placebo in the symptomatic treatment of patients with MS.
Data Sources
MEDLINE and the Cochrane Library Plus up to July 26, 2016. No restrictions were applied. The search was completed with information from ClinicalTrials.gov.
Study Selection
Randomized, double-blind, and placebo-controlled trials evaluating the effect of medicinal cannabinoids by oral or oromucosal route of administration on the symptoms of spasticity, pain, or bladder dysfunction in adult patients with MS.
Data Extraction and Synthesis
The Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) reporting guidelines were followed. Effect sizes were calculated as standardized mean difference (SMD) for efficacy, and rate ratio (RR) for tolerability. Within each study, those SMDs evaluating the same outcome were combined before the meta-analysis to obtain a single value per outcome and study. Pooling of the studies was performed on an intention-to-treat basis by means of random-effect meta-analysis.
Main Outcomes and Measures
Spasticity (on the Ashworth and Modified Ashworth scales and subjective), pain, bladder dysfunction, adverse events, and withdrawals due to adverse events.
Results
Seventeen selected trials including 3161 patients were analyzed. Significant findings for the efficacy of cannabinoids vs placebo were SMD = −0.25 SD (95% CI, −0.38 to −0.13 SD) for spasticity (subjective patient assessment data), −0.17 SD (95% CI, −0.31 to −0.03 SD) for pain, and −0.11 SD (95% CI, −0.22 to −0.0008 SD) for bladder dysfunction. Results favored cannabinoids. Findings for tolerability were RR = 1.72 patient-years (95% CI, 1.46-2.02 patient-years) in the total adverse events analysis and 2.95 patient-years (95% CI, 2.14-4.07 patient-years) in withdrawals due to adverse events. Results described a higher risk for cannabinoids. The serious adverse events meta-analysis showed no statistical significance.
Conclusions and Relevance
The results suggest a limited efficacy of cannabinoids for the treatment of spasticity, pain, and bladder dysfunction in patients with MS. Therapy using these drugs can be considered as safe.
Trial Registration
PROSPERO Identifier: CRD42014015391
Bladder-related pain is one of the most common forms of visceral pain, and visceral pain is among the most common complaints for which patients seek physician consultation. Despite extensive studies of visceral innervation and treatment of visceral pain, opioids remain a mainstay for management of bladder pain. Side effects associated with opioid therapy can profoundly diminish quality of life, and improved options for treatment of bladder pain remain a high priority. Endocannabinoids, primarily anandamide (AEA) and 2-arachidonoylglycerol (2-AG), are endogenously-produced fatty acid ethanolamides with that induce analgesia. Animal experiments have demonstrated that inhibition of enzymes that degrade AEA or 2-AG have the potential to prevent development of visceral and somatic pain. Although experimental results in animal models have been promising, clinical application of this approach has proven difficult. In addition to fatty acid amide hydrolase (FAAH; degrades AEA) and monacylglycerol lipase (MAGL; degrades 2-AG), cyclooxygenase (COX) acts to metabolize endocannabinoids. Another potential limitation of this strategy is that AEA activates pro-nociceptive transient receptor potential vanilloid 1 (TRPV1) channels. Dual inhibitors of FAAH and TRPV1 or FAAH and COX have been synthesized and are currently undergoing preclinical testing for efficacy in providing analgesia. Local inhibition of FAAH or MAGL within the bladder may be viable options to reduce pain associated with cystitis with fewer systemic side effects, but this has not been explored. Further investigation is required before manipulation of the endocannabinoid system can be proven as an efficacious alternative for management of bladder pain.
The therapeutic application of Cannabis is attracting substantial public and clinical interest. The Cannabis plant has been described as a veritable ‘treasure trove’, producing more than a hundred different cannabinoids, although the focus to date has been on the psychoactive molecule delta‐9‐tetraydrocannabinol (THC) and cannabidiol (CBD). Other numerous secondary metabolites of Cannabis the terpenes, some of which share the common intermediary geranyl diphosphate (GPP) with the cannabinoids, are hypothesised to contribute synergistically to their therapeutic benefits, an attribute that has been described as the ‘entourage effect’. The effective delivery of such a complex multicomponent pharmaceutical relies upon the stable genetic background and standardised growth of the plant material, particularly if the raw botanical product in the form of the dried pistillate inflorescence (flos) is the source. Following supercritical CO2 extraction of the inflorescence (and possibly bracts), the secondary metabolites can be blended to provide a specific ratio of major cannabinoids (THC:CBD) or individual cannabinoids can be isolated, purified and supplied as the pharmaceutical. Intensive breeding strategies will provide novel cultivars of Cannabis possessing elevated levels of specific cannabinoids or other secondary metabolites.
The biological effects of cannabinoids, the major constituents of the ancient medicinal plantCannabis sativa(marijuana) are mediated by two members of the G-protein coupled receptor family, cannabinoid receptors 1 (CB1R) and 2. The CB1R is the prominent subtype in the central nervous system (CNS) and has drawn great attention as a potential therapeutic avenue in several pathological conditions, including neuropsychological disorders and neurodegenerative diseases. Furthermore, cannabinoids also modulate signal transduction pathways and exert profound effects at peripheral sites. Although cannabinoids have therapeutic potential, their psychoactive effects have largely limited their use in clinical practice. In this review, we briefly summarized our knowledge of cannabinoids and the endocannabinoid system, focusing on the CB1R and the CNS, with emphasis on recent breakthroughs in the field. We aim to define several potential roles of cannabinoid receptors in the modulation of signaling pathways and in association with several pathophysiological conditions. We believe that the therapeutic significance of cannabinoids is masked by the adverse effects and here alternative strategies are discussed to take therapeutic advantage of cannabinoids.
Purpose of review:
Pharmaceutical cannabinoids such as nabiximols, nabilone and dronabinol, and plant-based cannabinoids have been investigated for their therapeutic potential in treating multiple sclerosis (MS) symptoms. This review of reviews aimed to synthesise findings from high quality systematic reviews that examined the safety and effectiveness of cannabinoids in multiple sclerosis. We examined the outcomes of disability and disability progression, pain, spasticity, bladder function, tremor/ataxia, quality of life and adverse effects.
Recent findings:
We identified 11 eligible systematic reviews providing data from 32 studies, including 10 moderate to high quality RCTs. Five reviews concluded that there was sufficient evidence that cannabinoids may be effective for symptoms of pain and/or spasticity in MS. Few reviews reported conclusions for other symptoms. Recent high quality reviews find cannabinoids may have modest effects in MS for pain or spasticity. Future research should include studies with non-cannabinoid comparators; this is an important gap in the evidence.
The authors review the historical use of medicinal cannabis and discuss the agent’s pharmacology and pharmacokinetics, select evidence on medicinal uses, and the implications of evolving regulations on the acute care hospital setting.
Chronic prostatitis/chronic pelvic pain syndrome (CP/CPPS) is a chronic pelvic pain condition largely refractory to treatment. Cannabis (marijuana) use has been reported for a wide variety of chronic pain conditions, but no study has examined prevalence of cannabis use, symptom benefit or side effects, or frequency in CP/CPPS.
Participants were recruited from an outpatient CP/CPPS urology clinic (n = 98) and online through the Prostatitis Foundation website (n = 244). Participants completed questionnaires (demographics, CP/CPPS, depression, cannabis).
The clinic sample included Canadian patients and the online sample included primarily American patients. Due to differences, groups were examined separately. Almost 50% of respondents reported using cannabis (clinic n = 49; online n = 89). Of the cannabis users, 36.8% of clinic and 75% of online respondents reported that it improved their symptoms. Most of the respondents (from the clinic and online groups) reported that cannabis improved their mood, pain, muscle spasms, and sleep. However, they did not note any improvements for weakness, fatigue, numbness, ambulation, and urination. Overall, the effectiveness of cannabis for CP/CPPS was "somewhat/very effective" (57% clinic; 63% online). There were no differences between side effects or choice of consumption and most reported using cannabis rarely.
These are the first estimates in men suffering from CP/CPPS and suggest that while cannabis use is prevalent, its medical use and benefit are unknown. This is an understudied area and the benefit or hazard for cannabis use awaits further study.
As marijuana use becomes legal in some states, the dominant public opinion is that marijuana is a harmless source of mood alteration. Although the harms associated with marijuana use have not been well studied, enough information is available to cause concern.
2-Arachidonoyl-glycerol (2-Ara-Gl) has been isolated from various tissues and identified as an endogenous ligand for both cannabinoid receptors, CB1 and CB2. Here we report that in spleen, as in brain and gut, 2-Ara-Gl is accompanied by several 2-acyl-glycerol esters, two major ones being 2-linoleoyl-glycerol (2-Lino-Gl) and 2-palmitoyl-glycerol (2-Palm-Gl). These two esters do not bind to the cannabinoid receptors, nor do they inhibit adenylyl cyclase via either CB1 or CB2; however, they significantly potentiate the apparent binding of 2-Ara-Gl and its apparent capacity to inhibit adenylyl cyclase. Together these esters also significantly potentiate 2-Ara-Gl inhibition of motor behavior, immobility on a ring, analgesia on a hot plate and hypothermia caused by 2-Ara-Gl in mice. 2-Lino-Gl, but not 2-Palm-Gl, significantly inhibits the inactivation of 2-Ara-Gl by neuronal and basophilic cells. These data indicate that the biological activity of 2-Ara-Gl can be increased by related, endogenous 2-acyl-glycerols, which alone show no significant activity in any of the tests employed. This effect (`entourage effect') may represent a novel route for molecular regulation of endogenous cannabinoid activity.
Systemic administration of cannabinoid agonists is known to reduce pain induced by bladder inflammation and to modulate cystometric parameters in vivo. We have previously reported that intravesical administration of a cannabinoid agonist reduces the electrical activity of bladder afferents under normal conditions. However, the effects of local activation of bladder cannabinoid receptors on afferent activity during inflammation are unknown. This study was aimed to assess the effects of intravesical administration of a cannabinoid agonist on the discharges of afferent fibers in inflamed bladders ex vivo. We also characterized the expression of CB1 receptors in the bladder and their localization and co-expression with TRPV1, a marker of nociceptive afferents.
Compared to untreated animals, afferent fiber activity in inflamed bladders was increased for intravesical pressures between 10 and 40 mmHg. Local treatment with a non selective cannabinoid agonist (AZ12646915) significantly reduced the afferent activity at intravesical pressures above 20 mmHg. This effect was blocked by AM251 but not by AM630 (selective for CB1 and CB2 respectively). Finally, CB1 was co-expressed with TRPV1 in control and inflamed bladders.
These results demonstrate that sensitization of bladder afferents induced by inflammation is partly suppressed by intravesical activation of cannabinoid receptors, an effect that appears to be mediated by CB1 receptors. Also, TRPV1 positive fibers were found to co-express CB1, supporting the hypothesis of a direct action of the cannabinoid agonist on nociceptive afferents. Taken together, these results indicate a peripheral modulation by the cannabinoid system of bladder hypersensitivity during inflammation.
Cannabinoids, the active components of Cannabis sativa (maijuana), and their derivatives produce a wide spectrum of central and peripheral effects, some of which may have clinical applications. The discovery of specific cannabinoid receptors and a family of endogenous ligands of those receptors has attracted much attention to the general cannabinoid pharmacology. In recent years, studies on the functional role of cannabinoid receptors in bladder have been motivated by the therapeutic effects of cannabinoids on voiding dysfunction in multiple sclerosis patients. In this review, we shall summarize the literature on the expression of cannabinoid receptors in urinary bladder and the peripheral influence of locally and systemically administered cannabinoids in the bladder. The ongoing search for cannabinoid-based therapeutic strategies devoid of psychotropic effects can be complemented with local delivery into bladder by the intravesical route. A greater understanding of the role of the peripheral CB(1) and CB(2) receptor system in lower urinary tract is necessary to allow the development of new treatment for pelvic disorders.
The cannabinoid receptor 1 (CB(1)) and CB(2) cannabinoid receptors, associated with drugs of abuse, may provide a means to treat pain, mood, and addiction disorders affecting widespread segments of society. Whether the orphan G-protein coupled receptor GPR55 is also a cannabinoid receptor remains unclear as a result of conflicting pharmacological studies. GPR55 has been reported to be activated by exogenous and endogenous cannabinoid compounds but surprisingly also by the endogenous non-cannabinoid mediator lysophosphatidylinositol (LPI). We examined the effects of a representative panel of cannabinoid ligands and LPI on GPR55 using a beta-arrestin-green fluorescent protein biosensor as a direct readout of agonist-mediated receptor activation. Our data demonstrate that AM251 and SR141716A (rimonabant), which are cannabinoid antagonists, and the lipid LPI, which is not a cannabinoid receptor ligand, are GPR55 agonists. They possess comparable efficacy in inducing beta-arrestin trafficking and, moreover, activate the G-protein-dependent signaling of protein kinase CbetaII. Conversely, the potent synthetic cannabinoid agonist CP55,940 acts as a GPR55 antagonist/partial agonist. CP55,940 blocks GPR55 internalization, the formation of beta-arrestin GPR55 complexes, and the phosphorylation of ERK1/2; CP55,940 produces only a slight amount of protein kinase CbetaII membrane recruitment but does not stimulate membrane remodeling like LPI, AM251, or rimonabant. Our studies provide a paradigm for measuring the responsiveness of GPR55 to a variety of ligand scaffolds comprising cannabinoid and novel compounds and suggest that at best GPR55 is an atypical cannabinoid responder. The activation of GPR55 by rimonabant may be responsible for some of the off-target effects that led to its removal as a potential obesity therapy.
The CNS contains a putative cannabinergic neurotransmitter and an abundance of G-protein-coupled cannabinoid receptors. However, little is known about the function of this novel neurochemical system. Cannabinold agonists produce antinociception in behavioral tests, suggesting the possibility that this system serves in part to modulate pain sensitivity. To explore this possibility, the effects of the cannabinoid agonist WIN 55,212-2 on nociceptive neurons in the ventroposterolateral (VPL) nucleus of the thalamus were examined in urethane-anesthetized rats. After identification of a nociresponsive neuron, a computer-controlled device delivered graded pressure stimuli to the contralateral hindpaw. WIN 55,212-2 (0.0625, 0.125, and 0.25 mg/kg, i.v.) suppressed noxious stimulus-evoked activity of VPL neurons in a dose-dependent and reversible manner. Noxious stimulus-evoked firing was affected more than spontaneous firing. These effects were apparently mediated by cannabinoid receptors, because the cannabinoid receptor-inactive enantiomer of the drug (WIN 55,212-3, 0.25 mg/kg) failed to alter the activity of this population of cells. Administration of morphine (0.5 mg/kg, i.v.) produced effects that were very similar to those produced by the cannabinoid. WIN 55,212-2 (0.25 mg/kg, i.v.) failed to alter the responses of non-nociceptive low-threshold mechanosensitive neurons in the VPL WIN 55,212-2 produced antinociceptive effects with a potency and time course similar to that observed in the electrophysiological experiments, despite the differences in the anesthetic states of the animals used in these experiments. The antinociceptive and electrophysiological effects on VPL neurons outlasted the motor effects of the drug. Furthermore, the changes in nociceptive responding could not be attributed to changes in skin temperature. Taken together, these findings suggest that cannabinoids decrease nociceptive neurotransmission at the level of the thalamus and that one function of endogenous cannabinoids may be to modulate pain sensitivity.
was seen only in the presence of GTP and was sensi- tive to pertussis toxin pre-treatment, indicating a response mediated by Gi/Go G-protein, 46 48 fu rther indication of the presence of a cannabinoid receptor. The low potency and high lipophilicity of the cannabinoids led to the search for synthetic com- pounds with cannabamimetic activity.
Dronabinol (Delta 9-tetrahydocannabinol, THC), the main source of the pharmacological effects caused by the use of cannabis, is an agonist to both the CB1 and the CB2 subtype of cannabinoid receptors. It is available on prescription in several countries. The non-psychotropic cannabidiol (CBD), some analogues of natural cannabinoids and their metabolites, antagonists at the cannabinoid receptors and modulators of the endogenous cannabinoid system are also promising candidates for clinical research and therapeutic uses. Cannabinoid receptors are distributed in the central nervous system and many peripheral tissues including spleen, leukocytes; reproductive, urinary and gastrointestinal tracts; endocrine glands, arteries and heart. Five endogenous cannabinoids have been detected so far, of whom anandamide and 2-arachidonylglycerol are best characterized. There is evidence that besides the two cannabinoid receptor subtypes cloned so far additional cannabinoid receptor subtypes and vanilloid receptors are involved in the complex physiological functions of the cannabinoid system that include motor coordination, memory procession, control of appetite, pain modulation and neuroprotection. Strategies to modulate their activity include inhibition of re-uptake into cells and inhibition of their degradation to increase concentration and duration of action. Properties of cannabinoids that might be of therapeutic use include analgesia, muscle relaxation, immunosuppression, anti-inflammation, anti-allergic effects, sedation, improvement of mood, stimulation of appetite, anti-emesis, lowering of intraocular pressure, bronchodilation, neuroprotection and antineoplastic effects.
Olvanil (N-9-Z-octadecenoyl-vanillamide) is an agonist of transient receptor potential vanilloid type 1 (TRPV1) channels that lack the pungency of capsaicin and was developed as an oral analgesic. Vanillamides are unmatched in terms of structural simplicity, straightforward synthesis, and safety compared with the more powerful TRPV1 agonists, like the structurally complex phorboid compound resiniferatoxin. We have modified the fatty acyl chain of olvanil to obtain ultra-potent analogs. The insertion of a hydroxyl group at C-12 yielded a compound named rinvanil, after ricinoleic acid, significantly less potent than olvanil (EC(50) = 6 versus 0.7 nM), but more versatile in terms of structural modifications because of the presence of an additional functional group. Acetylation and phenylacetylation of rinvanil re-established and dramatically enhanced, respectively, its potency at hTRPV1. With a two-digit picomolar EC(50) (90 pM), phenylacetylrinvanil (PhAR, IDN5890) is the most potent vanillamide ever described with potency comparable with that of resiniferatoxin (EC(50), 11 pM). Benzoyl- and phenylpropionylrinvanil were as potent and less potent than PhAR, respectively, whereas configurational inversion to ent-PhAR and cyclopropanation (but not hydrogenation or epoxidation) of the double bond were tolerated. Finally, iodination of the aromatic hydroxyl caused a dramatic switch in functional activity, generating compounds that behaved as TRPV1 antagonists rather than agonists. Since the potency of PhAR was maintained in rat dorsal root ganglion neurons and, particularly, in the rat urinary bladder, this compound was investigated in an in vivo rat model of urinary incontinence and proved as effective as resiniferatoxin at reducing bladder detrusor overactivity.
The role of anandamide in the development of inflammatory hyperalgesia and visceral hyperreflexia was studied in the rat urinary bladder. Animals were given intraperitoneal cyclophosphamide injection, which evokes painful hemorrhagic cystitis accompanied by increased bladder reflex activity. The vanilloid receptor 1 [transient receptor potential vanilloid 1 (TRPV1)] antagonist capsazepine, applied onto the serosal surface of bladders, significantly reduced the hyperreflexia. Mass spectrometric analysis revealed that cyclophosphamide injection significantly and persistently increased the anandamide content of bladder tissues. The increase in the anandamide content paralleled the development of reflex hyperactivity. Anandamide (1-100 microm), applied onto the serosal surface of naive bladders, increased the reflex activity in a concentration-dependent manner. Repeated anandamide applications did not produce desensitization of the response. The anandamide-evoked effect was blocked by capsazepine or by instillation of resiniferatoxin, the ultrapotent TRPV1 agonist, into the bladders 24 hr before the anandamide challenge. The cannabinoid 1 receptor antagonist SR141716A [N-piperidino-5-(4-chlorophenyl)-1-(2,4-dichlorophenyl)-4-methylpyrazole-3-carboxamide] significantly increased the potency of anandamide in enhancing bladder reflex activity in naive but not in cyclophosphamide-injected animals. Application of the fatty acid amide hydrolyze inhibitor palmitoylisopropylamine onto the serosal surface of bladders also increased the reflex activity both in naive and cyclophosphamide-injected rats. This latter effect in naive animals was blocked by capsazepine and by resiniferatoxin pretreatment. Finally, intravesical instillation of anandamide (50 microm) increased c-fos expression in the spinal cord, which was reduced by capsazepine or by resiniferatoxin pretreatment. These results suggest that anandamide, through activating TRPV1, contributes to the development of hyperreflexia and hyperalgesia during cystitis.
To test whether cannabinoids reduce urge incontinence episodes without affecting voiding in patients with multiple sclerosis. This was part of the multicentre trial of the Cannabinoids in Multiple Sclerosis (CAMS) study.
The CAMS study randomised 630 patients to receive oral administration of cannabis extract, Delta(9)-tetrahydrocannabinol (THC) or matched placebo. For this substudy subjects completed incontinence diaries.
All three groups showed a significant reduction, p<0.01, in adjusted episode rate (i.e. correcting for baseline imbalance) from baseline to the end of treatment: cannabis extract, 38%; THC, 33%; and placebo, 18%. Both active treatments showed significant effects over placebo (cannabis extract, p=0.005; THC, p=0.039).
The findings are suggestive of a clinical effect of cannabis on incontinence episodes in patients with MS. This is in contrast to the negative finding of the CAMS study, where no difference was seen in the primary outcome of spasticity.
Cannabinoids are a class of pharmacologic compounds that offer potential applications as antitumor drugs, based on the ability of some members of this class to limit inflammation, cell proliferation, and cell survival. In particular, emerging evidence suggests that agonists of cannabinoid receptors expressed by tumor cells may offer a novel strategy to treat cancer. Here, we review recent work that raises interest in the development and exploration of potent, nontoxic, and nonhabit forming cannabinoids for cancer therapy.
The Cannabis plant has been used for many of years as a medicinal agent in the relief of pain and seizures. It contains approximately 540 natural compounds including more than 100 that have been identified as phytocannabinoids due to their shared chemical structure. The predominant psychotropic component is Δ⁹-tetrahydrocannabinol (Δ⁹-THC), while the major non-psychoactive ingredient is cannabidiol (CBD). These compounds have been shown to be partial agonists or antagonists at the prototypical cannabinoid receptors, CB1 and CB2. The therapeutic actions of Δ⁹-THC and CBD include an ability to act as analgesics, anti-emetics, anti-inflammatory agents, anti-seizure compounds and as protective agents in neurodegeneration. However, there is a lack of well-controlled, double blind, randomized clinical trials to provide clarity on the efficacy of either Δ⁹-THC or CBD as therapeutics. Moreover, the safety concerns regarding the unwanted side effects of Δ⁹-THC as a psychoactive agent preclude its widespread use in the clinic. The legalization of cannabis for medicinal purposes and for recreational use in some regions will allow for much needed research on the pharmacokinetics and pharmocology of medical cannabis. This brief review focuses on the use of cannabis as a medicinal agent in the treatment of pain, epilepsy and neurodegenerative diseases. Despite the paucity of information, attention is paid to the mechanisms by which medical cannabis may act to relieve pain and seizures.
INTRODUCTION
Chronic pelvic pain (CPP) is a prevalent but difficult entity to treat. Cannabis has been shown to significantly improve pain in several populations. There have been no studies on cannabis use among women with CPP. We aim to examine the prevalence of cannabis use in patients with CPP and hypothesize that CPP patients report an improvement in their pain symptoms with cannabis use.
METHODS
Patients were identified via a medical record query of commonly used CPT codes for pelvic pain. Patients were contacted via phone then emailed an anonymous online survey. Setting: Tertiary care academic medical center.
RESULTS
114 patients who screened positive for CPP over the phone were emailed; 89 responded for a response rate of 78.1%. The prevalence of current use was 16.9% (14/83). Nine of fourteen (64.3%) current users reported using cannabis for CPP while 8/24 (33.3%) of previous users reported using cannabis for CPP; all 17 (100%) reported that it was helpful. The users who reported using cannabis for CPP reported an average reduction in pain by 5.9 points (P<.0001) and those who did not report using cannabis for CPP also reported a reduction in pain by 2.9 points (P=.0012). 71/82 (86.6%) respondents would consider being in a clinical trial of medical cannabis to treat CPP.
CONCLUSION
This study demonstrates that patients with CPP are self-treating with cannabis and finding this to be an effective intervention. Cannabis may serve as a future treatment option for females with CPP if found to be safe and effective. Clinical trials are needed.
Cannabinoid receptors, endocannabinoids and the enzymes responsible for their biosynthesis and degradation constitute the endocannabinoid system. In recent decades, the endocannabinoid system has attracted considerable interest as a potential therapeutic target in numerous pathological conditions. Its involvement in several physiological processes is well known, such as in energy balance, appetite stimulation, blood pressure, pain modulation, embryogenesis, nausea and vomiting control, memory, learning and immune response, among others, as well as in pathological conditions where it exerts a protective role in the development of certain disorders. As a result, it has been reported that changes in endocannabinoid levels may be related to neurological diseases such as Parkinson’s disease, Huntington’s disease, Alzheimer’s disease and multiple sclerosis, as well as anorexia and irritable bowel syndrome. Alterations in the endocannabinoid system have also been associated with cancer, affecting the growth, migration and invasion of some tumours. Cannabinoids have been tested in several cancer types, including brain, breast and prostate cancers. Cannabinoids have shown promise as analgesics for the treatment of both inflammatory and neuropathic pain. There is also evidence for a role of the endocannabinoid system in the control of emotional states, and cannabinoids could prove useful in decreasing and palliating post-traumatic stress disorder symptoms and anxiolytic disorders. The role of the endocannabinoid system in addictions has also been examined, and cannabinoids have been postulated as alternative and co-adjuvant treatments in some abuse syndromes, mainly in ethanol and opioid abuses. The expression of the endocannabinoid system in the eye suggests that it could be a potential therapeutic target for eye diseases. Considering the importance of the endocannabinoid system and the therapeutic potential of cannabinoids in this vast number of medical conditions, several clinical studies with cannabinoid-based medications are ongoing. In addition, some cannabinoid-based medications have already been approved in various countries, including nabilone and dronabinol capsules for the treatment of nausea and vomiting associated with chemotherapy, dronabinol capsules for anorexia, an oral solution of dronabinol for both vomiting associated with chemotherapy and anorexia, a Δ⁹-tetrahydrocannabinol/cannabidiol oromucosal spray for pain related to cancer and for spasticity and pain associated with multiple sclerosis, and an oral solution of cannabidiol for Dravet and Lennox–Gastaut syndromes. Here, we review the available efficacy, safety and tolerability data for cannabinoids in a range of medical conditions.
Aberrant activation of toll-like receptor (TLR)s results in persistent and prolonged neuroinflammation and has been implicated in the pathogenesis and exacerbation of psychiatric and neurodegenerative disorders. TLR3 coordinates the innate immune response to viral infection and recent data have demonstrated that inhibiting fatty acid amide hydrolase (FAAH), the enzyme that primarily metabolizes anandamide, modulates TLR3-mediated neuroinflammation. However, the physiological and behavioural consequences of such modulation are unknown. The present study examined the effect of URB597, a selective FAAH inhibitor, on neuroinflammation, physiological and behavioural alterations following administration of the TLR3 agonist and viral mimetic poly I:C to female rats. URB597 attenuated TLR3-mediated fever, mechanical and cold allodynia, and anxiety-like behaviour in the elevated plus maze and open field arena. There was no effect of URB597 on TLR3-mediated decreases in body weight and no effect in the sucrose preference or forced swim tests. URB597 attenuated the TLR3-mediated increase in the expression of CD11b and CD68, markers of microglia/macrophage activation. In summary, these data demonstrate that enhancing FAAH substrate levels suppresses TLR3-mediated microglia/macrophage activation and associated changes in fever, nociceptive responding and anxiety-related behaviour. These data provide further support for FAAH as a novel therapeutic target for neuroinflammatory disorders.
The endogenous cannabinoids anandamide and 2-arachidonoylglycerol bind to the cannabinoid receptors of type 1 and 2. These receptors are also the binding sites for exogenous, both natural and synthetic, cannabinoids that are used for recreation purposes. Until recently, cannabinoids and cannabinoid receptors have attracted little interest among nephrologists; however, a full endocannabinoid system (ECS) is present in the kidney and it has recently emerged as an important player in the pathogenesis of diabetic nephropathy, drug nephrotoxicity, and progressive chronic kidney disease. This newly established role of the ECS in the kidney might have therapeutic relevance, as pharmacological modulation of the ECS has renoprotective effects in experimental animals, raising hope for future potential applications in humans. In addition, over the last years, there has been a number of reported cases of acute kidney injury (AKI) associated with the use of synthetic cannabinoids that appear to have higher potency and rate of toxicity than natural Cannabis. This poorly recognized cause of renal injury should be considered in the differential diagnosis of AKI, particularly in young people. In this review we provide an overview of preclinical evidence indicating a role of the ECS in renal disease and discuss potential future therapeutic applications. Moreover, we give a critical update of synthetic cannabinoid-induced AKI.
Significance:
Redox imbalance may lead to overproduction of reactive oxygen and nitrogen species (ROS/RNS) and subsequent oxidative tissue damage which is a critical event in the course of neurodegenerative diseases. It is still not fully elucidated, however, whether oxidative stress is the primary trigger or a consequence in process of neurodegeneration. Recent Advances: Increasing evidence suggests that oxidative stress is involved in the propagation of neuronal injury and consequent inflammatory response, which in concert promote development of pathological alterations characteristic of most common neurodegenerative diseases. Critical Issue: Accumulating recent evidence also suggests that there is an important interplay between the lipid endocannabinoid system (ECS; comprising of the main cannabinoid 1 and 2 receptors (CB1 and CB2), endocannabinoids and their synthetic and metabolizing enzymes) and various key inflammatory and redox-dependent processes.
Future directions:
Targeting the ECS in order to modulate redox state-dependent cell death, and to decrease consequent or preceding inflammatory response holds therapeutic potential in multitude of oxidative stress-related acute or chronic neurodegenerative disorders from stroke and traumatic brain injury to Alzheimer`s and Parkinson`s diseases, and multiple sclerosis, just to name a few, which will be discussed in this overview.
Objectives:
To examine the effect of a peripherally active fatty acid amide hydrolase (FAAH-) inhibitor ASP3652 on safety and efficacy outcomes in Chronic Prostatitis/Chronic Pelvic Pain Syndrome (CP/CPPS). Inhibition of FAAH is hypothesized to reduce the excitability of urinary tract afferents including nociceptors.
Methods:
In this adaptive, randomized, double-blind, placebo-controlled study adult male patients with moderate to severe CP/CPPS were treated for 12 weeks with an oral dose of ASP3652 (25, 75, 150 or 300mg twice daily [BID], or 300mg once daily) or placebo. A Bayesian model was used for adaptive prospective modeling of randomization, study continuation decisions and analysis of the efficacy variables.
Results:
The study was stopped for futility at pre-planned interim analysis when 239 patients were randomized (226 were included in the intention-to-treat set): the 25mg group showed the largest reduction of the primary endpoint NIH-CPSI total score (7.0 points), but the placebo group showed a mean reduction of 7.3 points (difference: 0.3 [95% confidence interval: -1.9 to 2.6]). Micturition outcomes improved compared to placebo in all ASP3652 groups, e.g., in the 300mg bis in die (BID, twice daily) group voiding frequency decreased by -1.10 (95% CI -2.0 to -0.2) voids/24hr vs. placebo. Safety outcomes were comparable across the treatment groups.
Conclusions:
ASP3652 was generally safe and well-tolerated. It did not show efficacy on pain symptoms in patients with CP/CPPS. However, results indicate that FAAH-inhibition may attenuate lower urinary tract symptoms. Dedicated studies in patients with lower urinary tract dysfunction are needed to confirm this.
In the last decades, a number of new antimuscarinic drugs have been introduced for treatment of the overactive bladder (OAB), defined symptomatically (OAB syndrome) or urodynamically (detrusor overactivity). Recently, three new drug principles have been approved for clinical use, the β3 -adrenoceptor agonist, mirabegron, the phosphodiesterase 5-inhibitor, tadalafil, and the blocker of afferent and efferent nerves, botulinum toxin. However, new alternatives are continuously being explored. OAB is a filling disorder, and ATP is involved in the generation of afferent impulses. One way of blocking the ATP afferent pathway is through the use of P2X3 receptor antagonists. In animal models, this strategy appears to work very well, but whether it translates effectively to man remains to be established. Evidence suggests that components of the endocannabinoid system are involved in regulation of bladder function. Clinical studies of cannabinoid extracts on LUTS are scarce and essentially restricted to MS patients, and the results have so far not been convincing. Amplification of endocannabinoid activity by inhibiting their degradation via fatty acid amide hydrolase inhibitors may be an attractive approach, but no clinical experiences in OAB have been reported. Studies of the lower urinary tract have indicated that several transient receptor potential (TRP) channels, including TRPV1, TRPV2, TRPV4, TRPM8 and TRPA1, are expressed in the bladder and may act as sensors of stretch and/or chemical irritation. Animal studies have shown that inhibition of these pathways can be effective for the reduction of bladder activity. However, the roles of these channels for normal function and in pathological states have not been established, and so far adverse effects (hyperthermia) have hampered development of antagonists. This article is protected by copyright. All rights reserved.
Endocannabinoids, such as N-arachidonoylethanolamine (AEA, also called anandamide), exert potent analgesic and anti-inflammatory effects. Fatty acid amide hydrolase (FAAH) is primarily responsible for degradation of AEA, and deletion of FAAH increases AEA content in various tissues. Since FAAH has been shown to be present in the bladder of various species, we compared bladder function, severity of experimental cystitis, and cystitis-associated referred hyperalgesia in male wild-type (WT) and FAAH knock-out (KO) mice. Basal concentrations of AEA were greater, and the severity of cyclophosphamide (CYP)-induced cystitis was reduced in bladders from FAAH KO compared to WT mice. Cystitis-associated increased peripheral sensitivity to mechanical stimuli and enhanced bladder activity (as reflected by increased voiding frequency) were attenuated in FAAH KO compared to WT mice. Further, abundances of mRNA for several pro-inflammatory compounds were increased in the bladder mucosa after CYP treatment of WT mice, and this increase was inhibited in FAAH KO mice. These data indicate that endogenous substrates of FAAH, including the cannabinoid AEA, play an inhibitory role in bladder inflammation and subsequent changes in pain perception. Therefore, FAAH could be a therapeutic target to treat clinical symptoms of painful inflammatory bladder diseases.
To determine the efficacy of medical marijuana in several neurologic conditions.
We performed a systematic review of medical marijuana (1948-November 2013) to address treatment of symptoms of multiple sclerosis (MS), epilepsy, and movement disorders. We graded the studies according to the American Academy of Neurology classification scheme for therapeutic articles.
Thirty-four studies met inclusion criteria; 8 were rated as Class I.
The following were studied in patients with MS: (1) Spasticity: oral cannabis extract (OCE) is effective, and nabiximols and tetrahydrocannabinol (THC) are probably effective, for reducing patient-centered measures; it is possible both OCE and THC are effective for reducing both patient-centered and objective measures at 1 year. (2) Central pain or painful spasms (including spasticity-related pain, excluding neuropathic pain): OCE is effective; THC and nabiximols are probably effective. (3) Urinary dysfunction: nabiximols is probably effective for reducing bladder voids/day; THC and OCE are probably ineffective for reducing bladder complaints. (4) Tremor: THC and OCE are probably ineffective; nabiximols is possibly ineffective. (5) Other neurologic conditions: OCE is probably ineffective for treating levodopa-induced dyskinesias in patients with Parkinson disease. Oral cannabinoids are of unknown efficacy in non-chorea-related symptoms of Huntington disease, Tourette syndrome, cervical dystonia, and epilepsy. The risks and benefits of medical marijuana should be weighed carefully. Risk of serious adverse psychopathologic effects was nearly 1%. Comparative effectiveness of medical marijuana vs other therapies is unknown for these indications.
Fatty acid amide hydrolase (FAAH) degrades endocannabinoids and fatty acid amides. FAAH inhibition reduces micturition frequency and counteracts bladder overactivity in rats. We aimed to study the effects of a peripherally active selective FAAH inhibitor (URB937), and CB1- and CB2-receptor antagonist (rimonabant and SR144528) on single-unit afferent activities (SAAs) of the primary bladder afferents in rats.
Female Sprague-Dawley rats were anesthetized. SAAs of Aδ- or C-fibers from the L6 dorsal roots were recorded during bladder filling before and after URB937-administration with or without rimonabant or SR144528. Drugs were given intravenously (1mg/kg). Expressions of FAAH, CB1, or CB2, and the sensory marker CGRP in the L6 dorsal root ganglion (DRG) were compared by immunofluorescence.
One-hundred and two single afferent fibers (Aδ-fibers: n=48, C-fibers: n=54) were isolated from 57 rats. URB937 decreased C-fiber SAAs to 78 ± 9% and Aδ-fiber SAAs to 67 ± 7%, and increased bladder compliance to 116 ± 3 %. The effects of URB937 on SAAs and bladder compliance were counteracted by rimonabant or SR144528. Rimonabant increased SAAs of both fibers, while SR144528 only SAAs of Aδ-fibers. CGRP-positive L6 DRG neurons expressed strong FAAH, CB1 and CB2 stainings.
We show for the first time that inhibition of peripheral FAAH depresses Aδ- and C-fiber activities of primary bladder afferents via CB1- and CB2-receptors. CB antagonists alone exert facilitatory effects on SAAs during bladder filling in rats. The endocannabinoid system may be involved in the physiological control of micturition as regulators of afferent signals.
To review knowledge on cannabinoids and the endocannabinoid system in lower urinary tract function and dysfunction.
Review of MEDLINE using defined search terms, and manual analysis. Articles published in English were included.
Components of the endocannabinoid system-cannabinoid (CB) receptor types 1 and 2, anandamide, and fatty acid amide hydrolase (FAAH), which degrades anandamide and related fatty-acid amides-have been located to lower urinary tract tissues of mice, rats, monkeys, and humans. Studies have located CB receptors in urothelium and sensory nerves and FAAH in the urothelium. CB receptor- and FAAH-related activities have also been reported in the lumbosacral spinal cord. Data on supraspinal CB functions in relation to micturition are lacking. Cannabinoids are reported to reduce sensory activity of isolated tissues, cause antihyperalgesia in animal studies of bladder inflammation, affect urodynamics parameters reflecting sensory functions in animals models, and appear to have effects on storage symptoms in humans. FAAH inhibitors have affected sensory bladder functions and reduced bladder overactivity in rat models. Cannabinoids may modify nerve-mediated functions of isolated lower urinary tract tissues.
Evidence suggests components of the endocannabinoid system are involved in regulation of bladder function, possibly at several levels of the micturition pathway. It is unclear if either CB receptor has a dominant role in modification of sensory signals or if differences exist at peripheral and central nervous sites. Amplification of endocannabinoid activity by FAAH inhibitors may be an attractive drug target in specific pathways involved in LUTS. Neurourol. Urodynam. 9999:XX-XX, 2013. © 2013 Wiley Periodicals, Inc.
The endocannabinoid system is implicated in a variety of physiological and pathological conditions (inflammation, immunomodulation, analgesia, cancer and others). The main active ingredient of cannabis, Δ ⁹ ‐tetrahydrocannabinol (Δ ⁹ ‐THC), produces its effects through activation of CB 1 and CB 2 receptors. CB 1 receptors are expressed at high levels in the central nervous system (CNS), whereas CB 2 receptors are concentrated predominantly, although not exclusively, in cells of the immune system. Endocannabinoids are endogenous lipid‐signalling molecules that are generated in the cell membrane from phospholipid precursors. The two best characterized endocannabinoids identified to date are anandamide (AEA) and 2‐arachidonoylglycerol (2‐AG). Here we review the relationship between the endocannabinoid system and anti‐tumour actions (inhibition of cell proliferation and migration, induction of apoptosis, reduction of tumour growth) of the cannabinoids in different types of cancer. This review will focus on examining how activation of the endocannabinoid system impacts breast, prostate and bone cancers in both in vitro and in vivo systems. The therapeutic potential of cannabinoids for cancer, as identified in clinical trials, is also discussed. Identification of safe and effective treatments to manage and improve cancer therapy is critical to improve quality of life and reduce unnecessary suffering in cancer patients. In this regard, cannabis‐like compounds offer therapeutic potential for the treatment of breast, prostate and bone cancer in patients. Further basic research on anti‐cancer properties of cannabinoids as well as clinical trials of cannabinoid therapeutic efficacy in breast, prostate and bone cancer is therefore warranted.
LINKED ARTICLES This article is part of a themed issue on Cannabinoids in Biology and Medicine. To view the other articles in this issue visit http://dx.doi.org/10.1111/bph.2011.163.issue‐7
Referred hyperalgesia to a somatopically appropriate superficial site is a cardinal symptom of visceral inflammatory pain and has been demonstrated after turpentine-induced urinary bladder inflammation in the rat. The authors examined the effect of the endocannabinoids anandamide and palmitoylethanolamide on the referred hyperalgesia associated with this model.
After measurement of baseline limb withdrawal latencies to a noxious heat stimulus, the bladders of 50 female Wistar rats were inflamed by intravesical administration of 0.5 ml 50% turpentine. Ten or 25 mg/kg of anandamide or palmitoylethanolamide or vehicle were administered immediately before introduction of turpentine. Antagonists to both the cannabinoid CB1 and CB2 receptors were coadministered with the higher dose of endocannabinoids. Latencies were recorded 2, 4, 6, 8, and 24 h after removal of turpentine. The difference between forelimb and hind limb withdrawal latencies was plotted against time, and areas under these curves were compared.
Inflammation of the urinary bladder was associated with a relative thermal hyperalgesia referred to the hind limb. Anandamide and palmitoylethanolamide attenuated this referred hyperalgesia at doses of 10 and 25 mg/kg. The CB1 receptor antagonist SR141716A reduced the antihyperalgesic effect of anandamide, but the CB2 antagonist SR144528 did not. Coadministration of SR141716A with palmitoylethanolamide did not affect the antihyperalgesic effect but was reduced by SR144528.
Anandamide (via CB1 receptors) and palmitoylethanolamide (putatively via CB2 receptors) attenuated a referred hyperalgesia in a dose-dependent fashion. CB1 and CB2 receptors are strategically situated to influence the nerve growth factor-driven referred hyperalgesia associated with inflammation of the urinary bladder. These data implicate cannabinoids as a novel treatment for vesical pain.
There are at least two types of cannabinoid receptors, CB1 and CB2, both coupled to G proteins. CB1 receptors exist primarily on central and peripheral neurons, one of their functions being to modulate neurotransmitter release. CB2 receptors are present mainly on immune cells. Their roles are proving more difficult to establish but seem to include the modulation of cytokine release. Endogenous agonists for cannabinoid receptors (endocannabinoids) have also been discovered, the most important being arachidonoyl ethanolamide (anandamide), 2-arachidonoyl glycerol and 2-arachidonyl glyceryl ether. Other endocannabinoids and cannabinoid receptor types may also exist. Although anandamide can act through CB1 and CB2 receptors, it is also a vanilloid receptor agonist and some of its metabolites may possess yet other important modes of action. The discovery of the system of cannabinoid receptors and endocannabinoids that constitutes the ‘endocannabinoid system’ has prompted the development of CB1- and CB2-selective agonists and antagonists/inverse agonists. CB1/CB2 agonists are already used clinically, as anti-emetics or to stimulate appetite. Potential therapeutic uses of cannabinoid receptor agonists include the management of multiple sclerosis/spinal cord injury, pain, inflammatory disorders, glaucoma, bronchial asthma, vasodilation that accompanies advanced cirrhosis, and cancer. Following their release onto cannabinoid receptors, endocannabinoids are removed from the extracellular space by membrane transport and then degraded by intracellular enzymic hydrolysis. Inhibitors of both these processes have been developed. Such inhibitors have therapeutic potential as animal data suggest that released endocannabinoids mediate reductions both in inflammatory pain and in the spasticity and tremor of multiple sclerosis. So too have CB1 receptor antagonists, for example for the suppression of appetite and the management of cognitive dysfunction or schizophrenia.
Contemporary medicine is characterized by sophisticated specialization of the individual physician. The specialist in urological surgery may undertake one of the most important and primary medical tasks, the mitigation and therapy of pain. This review aims to provide an overview of the concepts of pain therapy in urology. Most patients benefit from basic concepts of analgesia, including measuring and documenting pain scores at the bedside by the nursing staff. Patients undergoing very painful operative procedures require more potent techniques of analgesia, e.g. intravenous patient-controlled analgesia and epidural analgesia. These techniques need adequate supervision by an acute pain service, but their implementation improves the outcome in some situations. Pain in acute renal obstruction varies in intensity and duration; hence, analgesic therapy has to be tailored to the individual patient. Pain syndromes from cancer can be more complex than those after surgery. Neuropathic pain is probably the most difficult to manage and requires consultation with a pain-management specialist. In the case of neuropathic pain, treatment only with opioids is of limited efficacy and combination with co-analgesics is necessary. In addition, invasive analgesic therapies should sometimes be considered.
Urinary incontinence and overactive bladder are important and common conditions that have received little general medical attention. We reviewed the magnitude and impact of these conditions, and discuss pharmacotherapy as well as new drugs under investigation.
The main emphasis of this review is pharmacological therapy for the bladder. We discuss currently available agents, drugs under development and pharmacological targets that would be suitable targets for treating overactive bladder. Drugs such as duloxetine that target not bladder smooth muscle, but rather central nervous system control of the micturition reflex are undergoing clinical trials. We also discuss intravesical therapy and alternative drug delivery methods, such as intravesical capsaicin and botulinum toxin, with special emphasis on approaches to modulate bladder afferent nerve function for preventing overactive bladder.
There are many advantages to advanced drug delivery systems, including long-term therapeutic efficacy, decreased side effects and improved patient compliance. Future speculation such as gene therapy holds great promise for overactive bladder because it is possible to access all genitourinary organs via endoscopy and other minimally invasive techniques that are ideally suited for gene therapy.
Traditional anticholinergic therapies are limited in their effectiveness. There is great hope for future research regarding voiding dysfunction and urinary incontinence through a focus on afferent nerve intervention for preventing overactive bladder.
Chronic prostatitis/chronic pelvic pain syndrome (CP/CPPS) is a common condition, affecting men of all ages. Since mortality and serious complications are extremely uncommon, CP/CPPS is primarily a quality-of-life disease, and, therefore, the patient's perspective is of paramount importance. As with other non-life threatening diseases, the goal of treatment is to maximize quality not quantity of life. Scientifically validated methods to measure patients' health related quality of life have been applied in other urological diseases such as benign prostatic hyperplasia and interstitial cystitis; the same process is now underway in the study of CP/CPPS. Recent studies have shown that CP/CPPS takes a substantial toll on physical and mental health. In addition to examining the health related quality of life of patients with CP/CPPS, future studies should address additional patient-centered outcomes, such as satisfaction with care and the economic burden of the illness, in order to allow a more comprehensive understanding of the impact of this condition on patients.
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.
Cannabis has been known as a medicine for several thousand years across many cultures. It reached a position of prominence within Western medicine in the nineteenth century but became mired in disrepute and legal controls early in the twentieth century. Despite unremitting world-wide suppression, recreational cannabis exploded into popular culture in the 1960s and has remained easily obtainable on the black market in most countries ever since. This ready availability has allowed many thousands of patients to rediscover the apparent power of the drug to alleviate symptoms of some of the most cruel and refractory diseases known to humankind. Pioneering clinical research in the last quarter of the twentieth century has given some support to these anecdotal reports, but the methodological challenges to human research involving a pariah drug are formidable. Studies have tended to be small, imperfectly controlled, and have often incorporated unsatisfactory synthetic cannabinoid analogues or smoked herbal material of uncertain composition and irregular bioavailability. As a result, the scientific evaluation of medicinal cannabis in humans is still in its infancy. New possibilities in human research have been opened up by the discovery of the endocannabinoid system, a rapidly expanding knowledge of cannabinoid pharmacology, and a more sympathetic political environment in several countries. More and more scientists and clinicians are becoming interested in exploring the potential of cannabis-based medicines. Future targets will extend beyond symptom relief into disease modification, and already cannabinoids seem to offer particular promise in the treatment of certain inflammatory and neurodegenerative conditions. This chapter will begin with an outline of the development and current status of legal controls pertaining to cannabis, following which the existing human research will be reviewed. Some key safety issues will then be considered, and the chapter will conclude with some suggestions as to future directions for human research.
The transient receptor potential vanilloid subfamily 1 (TRPV1) is an ion channel activated by capsaicin, heat, protons and endogenous ligands such as anandamide. It is largely expressed in the urinary tract of mammals. Structures in which the receptor expression is firmly established include sensory fibers and urothelial cells, although the presence of TRPV1 in other cell types has been reported. As in other systems, pain perception was the first role attributed to TRPV1 in the urinary tract. However, it is now increasingly clear that TRPV1 also regulates the frequency of bladder reflex contractions, either through direct excitation of sensory fibers or through urothelial-sensory fiber cross talk involving the release of neuromediators from the epithelial cells. In addition, the recent identification of the receptor in urothelial and prostatic cancer cells raise the exciting hypothesis that TRPV1 is involved in cell differentiation. Desensitization of the receptor by capsaicin and resiniferatoxin has been investigated for therapeutic purposes. For the moment, lower urinary tract dysfunctions in which some benefit was obtained include painful bladder syndrome and overactive bladder of neurogenic and non-neurogenic origin. However, desensitization may become obsolete when non-toxic, potent TRPV1 antagonists become available.
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Broyd N. Avoid many common treatments for chronic pain. Medscape: NICE. 2020;1:1-2.
Cannabinoid receptors and their ligands. Research Support, Non-U.S. Gov't Research Support, U.S. Gov't, P.H.S. Review
- Pertwee
Medical use of cannabinoids. Review
- Fraguas-Sanchez
Cannabinoids and the endocannabinoid system in lower urinary tract function and dysfunction. Review
- Hedlund
Pharmacology and potential therapeutic uses of cannabis. Review
- Hirst