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This literature survey aims to extend the comprehensive survey performed by Bergamaschi et al. Apart from updating the literature, this article focuses on clinical studies and CBD potential interactions with other drugs. In general, the often described favorable safety profile of CBD in humans was confirmed and extended by the reviewed research.
The majority of studies were performed for treatment of epilepsy and psychotic disorders. In comparison with other drugs, used for the treatment of these medical conditions, CBD has a better side effect profile.
This could improve patients' compliance and adherence to treatment. CBD is often used as adjunct therapy. Therefore, more clinical research is warranted on CBD action on hepatic enzymes, drug transporters, and interactions with other drugs and to see if this mainly leads to positive or negative effects, for example, reducing the needed clobazam doses in epilepsy and therefore clobazam's side effects.
This review also illustrates that some important toxicological parameters are yet to be studied, for example, if CBD has an effect on hormones. Additionally, more clinical trials with a greater number of participants and longer chronic CBD administration are still lacking. The most prominent of those is cannabidiol CBD.
For instance, it is anxiolytic, anti-inflammatory, antiemetic, and antipsychotic. Moreover, neuroprotective properties have been shown. At lower doses, it has physiological effects that promote and maintain health, including antioxidative, anti-inflammatory, and neuroprotection effects. For instance, CBD is more effective than vitamin C and E as a neuroprotective antioxidant and can ameliorate skin conditions such as acne.
The comprehensive review of original studies by Bergamaschi et al. Moreover, psychological and psychomotor functions are not adversely affected. The same holds true for gastrointestinal transit, food intake, and absence of toxicity for nontransformed cells. Nonetheless, some side effects have been reported for CBD, but mainly in vitro or in animal studies. They include alterations of cell viability, reduced fertilization capacity, and inhibition of hepatic drug metabolism and drug transporters e.
In these studies, a large enough number of subjects have to be enrolled to analyze long-term safety aspects and CBD possible interactions with other substances. This review will build on the clinical studies mentioned by Bergamaschi et al. Before we discuss relevant animal research on CBD possible effects on various parameters, several important differences between route of administration and pharmacokinetics between human and animal studies have to be mentioned.
First, CBD has been studied in humans using oral administration or inhalation. Administration in rodents often occures either via intraperitoneal injection or via the oral route. Second, the plasma levels reached via oral administration in rodents and humans can differ. Both these observations can lead to differing active blood concentrations of CBD. In addition, it is possible that CBD targets differ between humans and animals.
Therefore, the same blood concentration might still lead to different effects. Even if the targets, to which CBD binds, are the same in both studied animals and humans, for example, the affinity or duration of CBD binding to its targets might differ and consequently alter its effects.
The following study, which showed a positive effect of CBD on obsessive compulsive behavior in mice and reported no side effects, exemplifies the existing pharmacokinetic differences.
This higher bioavailability, in turn, can cause larger CBD effects. This calculation was performed assuming the pharmacokinetics of a hydrophilic compound, for simplicity's sake. We are aware that the actual levels of the lipophilic CBD will vary. A second caveat of preclinical studies is that supraphysiological concentrations of compounds are often used. This means that the observed effects, for instance, are not caused by a specific binding of CBD to one of its receptors but are due to unspecific binding following the high compound concentration, which can inactivate the receptor or transporter.
The following example and calculations will demonstrate this. This can have several implications because various anticancer drugs also bind to these membrane-bound, energy-dependent efflux transporters.
The rationale behind suggesting these concentrations is that studies summarized by Bih et al. It also seems warranted to assume that the mean plasma concentration exerts the total of observed CBD effects, compared to using peak plasma levels, which only prevail for a short amount of time. This paragraph describes CBD interaction with general drug -metabolizing enzymes, such as those belonging to the cytochrome P family. This might have an effect for coadministration of CBD with other drugs.
Various drugs such as ketoconazol, itraconazol, ritonavir, and clarithromycin inhibit this enzyme. It has to be pointed out though, that the in vitro studies used supraphysiological CBD concentrations. Studies in mice have shown that CBD inactivates cytochrome P isozymes in the short term, but can induce them after repeated administration. This is similar to their induction by phenobarbital, thereby implying the 2b subfamily of isozymes. Hexobarbital is a CYP2C19 substrate, which is an enzyme that can be inhibited by CBD and can consequently increase hexobarbital availability in the organism.
Recorcinol was also found to be involved in CYP induction. CYP1A1 can be found in the intestine and CBD-induced higher activity could therefore prevent absorption of cancerogenic substances into the bloodstream and thereby help to protect DNA. This means that they do not reduce CBD transport to the brain.
The same goes for gefitinib inhibition of Bcrp. These proteins are also expressed at the blood—brain barrier, where they can pump out drugs such as risperidone. This is hypothesized to be a cause of treatment resistance. Nicardipine was used as the BCRP substrate in the in vitro studies, where the Jar cell line showed the largest increase in BCRP expression correlating with the highest level of transport. The ex vivo study used the antidiabetic drug and BCRP substrate glyburide.
In this study, a dose—response curve should be established in male and female subjects CBD absorption was shown to be higher in women because the concentrations used here are usually not reached by oral or inhaled CBD administration.
Nonetheless, CBD could accumulate in organs physiologically restricted via a blood barrier. Some studies indicate that under certain circumstances, CBD acute anxiolytic effects in rats were reversed after repeated day administration of CBD.
Nonetheless, the behavioral tests for OBX-induced hyperactivity and anhedonia related to depression and open field test for anxiety in the CBD-treated OBX animals showed an improved emotional response. Using microdialysis, the researchers could also show elevated 5-HT and glutamate levels in the prefrontal cortex of OBX animals only.
This area was previously described to be involved in maladaptive behavioral regulation in depressed patients and is a feature of the OBX animal model of depression. The fact that serotonin levels were only elevated in the OBX mice is similar to CBD differential action under physiological and pathological conditions.
A similar effect was previously described in anxiety experiments, where CBD proved to be only anxiolytic in subjects where stress had been induced before CBD administration. Elevated glutamate levels have been proposed to be responsible for ketamine's fast antidepressant function and its dysregulation has been described in OBX mice and depressed patients.
Chronic CBD treatment did not elicit behavioral changes in the nonoperated mice. No adverse effects were reported in this study. Various studies on CBD and psychosis have been conducted. The two higher CBD doses had beneficial effects comparable to the atypical antipsychotic drug clozapine and also attenuated the MK effects on the three markers mentioned above. The publication did not record any side effects. One of the theories trying to explain the etiology of bipolar disorder BD is that oxidative stress is crucial in its development.
Whereas CBD did not have an effect on locomotion, it did increase brain-derived neurotrophic factor BDNF levels and could protect against amphetamine-induced oxidative damage in proteins of the hippocampus and striatum. No adverse effects were recorded in this study. Another model for BD and schizophrenia is PPI of the startle reflex both in humans and animals, which is disrupted in these diseases. CBD, which is nonhedonic, can reduce heroin-seeking behavior after, for example, cue-induced reinstatement.
In addition, the described study was able to replicate previous findings showing no CBD side effects on locomotor behavior. There are various mechanisms underlying neuroprotection, for example, energy metabolism whose alteration has been implied in several psychiatric disorders and proper mitochondrial functioning.
A study comparing acute and chronic CBD administration in rats suggests an additional mechanism of CBD neuroprotection: Mitochondrial activity was measured in the striatum, hippocampus, and the prefrontal cortex. Since the mitochondrial complexes I and II have been implied in various neurodegenerative diseases and also altered ROS reactive oxygen species levels, which have also been shown to be altered by CBD, this might be an additional mechanism of CBD-mediated neuroprotection.
In healthy cells, this can be interpreted as a way to protect against the higher ROS levels resulting from more mitochondrial activity. Another publication studied the difference of acute and chronic administration of two doses of CBD in nonstressed mice on anxiety. Already an acute i. Fifteen days of repeated i. However, the higher dose caused a decrease in neurogenesis and cell proliferation, indicating dissociation of behavioral and proliferative effects of chronic CBD treatment. The study does not mention adverse effects.
Numerous studies show the CBD immunomodulatory role in various diseases such as multiple sclerosis, arthritis, and diabetes. These animal and human ex vivo studies have been reviewed extensively elsewhere, but studies with pure CBD are still lacking. It would be especially interesting to study when CBD is proinflammatory and under which circumstances it is anti-inflammatory and whether this leads to side effects Burstein, Table 1 shows a summary of its anti-inflammatory actions; McAllister et al.
In case of Alzheimer's disease AD , studies in mice and rats showed reduced amyloid beta neuroinflammation linked to reduced interleukin [IL]-6 and microglial activation after CBD treatment.
This led to amelioration of learning effects in a pharmacological model of AD. The chronic study we want to describe in more detail here used a transgenic mouse model of AD, where 2.
CBD was able to prevent the development of a social recognition deficit in the AD transgenic mice. Using statistical analysis by analysis of variance, this was shown to be only a trend. This might have been caused by the high variation in the transgenic mouse group, though. This was probably due to already elevated cholesterol in the transgenic mice.
The study observed no side effects. After CBD treatment was stopped, observation continued until the mice were 24 weeks old. CBD increased IL levels, which is thought to act as an anti-inflammatory cytokine in this context. After inducing arthritis in rats using Freund's adjuvant, various CBD doses 0. CBD reduced joint swelling, immune cell infiltration. CBD was shown to be able to influence migratory behavior in cancer, which is also an important aspect of embryogenesis.
Helix-loop-helix Id proteins play a role in embryogenesis and normal development via regulation of cell differentiation. High Id1-levels were also found in breast, prostate, brain, and head and neck tumor cells, which were highly aggressive. In contrast, Id1 expression was low in noninvasive tumor cells. Id1 seems to influence the tumor cell phenotype by regulation of invasion, epithelial to mesenchymal transition, angiogenesis, and cell proliferation. There only seems to exist one study that could not show an adverse CBD effect on embryogenesis.
An in vitro study could show that the development of two-cell embryos was not arrested at CBD concentrations of 6. Various studies have been performed to study CBD anticancer effects. CBD every 3 days for a total of 28 weeks, almost completely reduced the development of metastatic nodules caused by injection of human lung carcinoma cells A in nude mice. The typical side effects of traditional anticancer medication, emesis, and collateral toxicity were not described in these studies.
Consequently, CBD could be an alternative to other MMP1 inhibitors such as marimastat and prinomastat, which have shown disappointing clinical results due to these drugs' adverse muscoskeletal effects. Two studies showed in various cell lines and in tumor-bearing mice that CBD was able to reduce tumor metastasis. CBD downregulated Id1 at promoter level and reduced tumor aggressiveness.
Moreover, to carry out these experiments, animals are often immunologically compromised, to avoid immunogenic reactions as a result to implantation of human cells into the animals, which in turn can also affect the results. Another approach was chosen by Aviello et al. After 3 months, the number of aberrant crypt foci, polyps, and tumors was analyzed. The high CBD concentration led to a significant decrease in polyps and a return to near-normal levels of phosphorylated Akt elevation caused by the carcinogen.
Animal studies summarized by Bergamaschi et al. Chronic administration 14 days, 2. This effect could be inhibited by coadministration of a CB2R antagonist.
The positive effects of CBD on hyperglycemia seem to be mainly mediated via CBD anti-inflammatory and antioxidant effects. In addition, treatment increased adiponectin and liver glycogen concentrations. CBD showed inhibition of testosterone oxidation in the liver. Motor function was also tested on a rotarod, which was also not affected by CBD administration. Static beam performance, as an indicator of sensorimotor coordination, showed more footslips in the CBD group, but CBD treatment did not interfere with the animals' speed and ability to complete the test.
Compared to other anticonvulsant drugs, this effect was minimal. CBD did not lead to adverse effects. In addition, psychomotor function and psychological functions were not disturbed. Interestingly, the CYP2C19 inhibitor omeprazole, used to treat gastroesophageal reflux, could not significantly affect the pharmacokinetics of CBD. Unfortunately, it was not mentioned whether this effect was mediated via the cytochrome P complex.
Another aspect, which has not been thoroughly looked at, to our knowledge, is that several cytochrome isozymes are not only expressed in the liver but also in the brain. It might be interesting to research organ-specific differences in the level of CBD inhibition of various isozymes.
Apart from altering the bioavailability in the overall plasma of the patient, this interaction might alter therapeutic outcomes on another level.
Generally, more human studies, which monitor CBD-drug interactions, are needed. In a double-blind, placebo-controlled crossover study, CBD was coadministered with intravenous fentanyl to a total of 17 subjects. This was followed by a single 0. This extensive tool tests, for example, 78 adverse effects divided into 23 categories corresponding to organ systems or body parts. No respiratory depression or cardiovascular complications were recorded during any test session.
The results of the evaluation of pharmacokinetics, to see if interaction between the drugs occurred, were as follows. No effect was evident for urinary CBD and metabolite excretion except at the higher fentanyl dose, in which CBD clearance was reduced. Importantly, fentanyl coadministration did not produce respiratory depression or cardiovascular complications during the test sessions and CBD did not potentiate fentanyl's effects.
No correlation was found between CBD dose and plasma cortisol levels. CBD did not worsen the adverse effects e. Coadministration was safe and well tolerated, paving the way to use CBD as a potential treatment for opioid addiction. A Dutch study compared subjective adverse effects of three different strains of medicinal cannabis, distributed via pharmacies, using VAS.
The 12 adjectives used for this study were as follows: This strain showed significantly lower levels of anxiety and dejection.
Moreover, appetite increased less in the high CBD strain. The review by Bergamaschi et al. This holds especially true for the extrapyramidal motor side effects elicited by classical antipsychotic medication. Order of drug administration was pseudorandomized across subjects, so that an equal number of subjects received any of the drugs during the first, second, or third session in a double-blind, repeated-measures, within-subject design.
This effect was caused by opposite neural activation of relevant brain areas. In addition, no effects on peripheral cardiovascular measures such as heart rate and blood pressure were measured.
A randomized, double-blind, crossover, placebo-controlled trial was conducted in 16 healthy nonanxious subjects using a within-subject design. The doses were selected to only evoke neurocognitive effects without causing severe toxic, physical, or psychiatric reactions. The physiological parameters, heart rate and blood pressure, were also monitored and no significant difference between the placebo and the CBD group was observed. A case study describes a patient treated for cannabis withdrawal according to the following CBD regimen: Hepatic enzymes were also measured daily, but no effect was reported.
Naturalistic studies with smokers inhaling cannabis with varying amounts of CBD showed that the CBD levels were not altering psychomimetic symptoms. CBD might work to alleviate disorders of addiction, by altering the attentive salience of drug cues. The study did not further measure side effects. CBD can also reduce heroin-seeking behaviors e. This was shown in the preclinical data mentioned earlier and was also replicated in a small double-blind pilot study with individuals addicted to opioids, who have been abstinent for 7 days.
One hour after the video session, subjective craving was already reduced after a single CBD administration. The effect persisted for 7 days after the last CBD treatment. Interestingly, anxiety measures were also reduced after treatment, whereas no adverse effects were described. A pilot study with 24 subjects was conducted in a randomized, double-blind, placebo-controlled design to evaluate the impact of the ad hoc use of CBD in smokers, who wished to stop smoking.
Pre- and post-testing for mood and craving of the participants was executed. Craving was assessed using the Tiffany Craving Questionnaire On day 1 and 7, exhaled CO was measured to test smoking status. Sedation, depression, and anxiety were evaluated with the MRS. At day 7, the anxiety levels for placebo and CBD group did not differ. CBD did not increase depression in contrast to the selective CB1 antagonist rimonabant. CBD might weaken the attentional bias to smoking cues or could have disrupted reconsolidation, thereby destabilizing drug-related memories.
To the best of our knowledge, no acute studies were performed that solely concentrated on CBD glycemic effects. Moreover, the only acute study that also measured CBD effect on appetite was the study we described above, comparing different cannabis strains. Growth hormone and prolactin levels were unchanged. Cannabis flavonoids in whole cannabis extracts may also contribute useful activity McPartland and Russo Cannflavin A, a flavone unique to cannabis, inhibits PGE-2 thirty times more potently than aspirin Barrett et al , but has not been subsequently investigated.
Very few randomized controlled trials RCTs have been conducted using smoked cannabis Campbell et al despite many anecdotal claims Grinspoon and Bakalar A recent brief trial of smoked cannabis 3. This short clinical trial also demonstrated prominent adverse events associated with intoxication. In Canada, 21 subjects with chronic pain sequentially smoked single inhalations of 25 mg of cannabis 0, 2. Even after political and legal considerations, it remains extremely unlikely that crude cannabis could ever be approved by the FDA as a prescription medicine as outlined in the FDA Botanical Guidance document Food and Drug Administration ; Russo b , due to a lack of rigorous standardization of the drug, an absence of Phase III clinical trials, and pulmonary sequelae bronchial irritation and cough associated with smoking Tashkin Although cannabis vaporizers reduce potentially carcinogenic polyaromatic hydrocarbons, they have not been totally eliminated by this technology Gieringer et al ; Hazekamp et al Two open label studies in France of oral dronabinol for chronic neuropathic pain in 7 subjects Clermont-Gnamien et al and 8 subjects Attal et al , respectively, failed to show significant benefit on pain or other parameters, and showed adverse event frequently requiring discontinuation with doses averaging 15— Dronabinol did demonstrate positive results in a clinical trial of multiple sclerosis pain in two measures Svendsen et al , but negative results in post-operative pain Buggy et al Table 1.
Another uncontrolled case report in three subjects noted relief of intractable pruritus associated with cholestatic jaundice employing oral dronabinol Neff et al Some authors have noted patient preference for whole cannabis preparations over oral THC Joy et al , and the contribution of other components beyond THC to therapeutic benefits McPartland and Russo THC absorption orally is slow and erratic with peak serum levels in 45— minutes or longer.
Systemic bioavailability is also quite low due to rapid hepatic metabolism on first pass to hydroxy-THC. A rectal suppository of THC-hemisuccinate is under investigation Broom et al , as are transdermal delivery techniques Challapalli and Stinchcomb The terminal half-life of THC is quite prolonged due to storage in body lipids Grotenhermen Nabilone Cesamet Figure 1 , is a synthetic dimethylheptyl analogue of THC British Medical Association that displays greater potency and prolonged half-life.
Serum levels peak in 1—4 hours Lemberger et al It was also primarily developed as an anti-emetic in chemotherapy, and was recently re-approved for this indication in the USA. Prior case reports have noted analgesic effects in case reports in neuropathic pain Notcutt et al and other pain disorders Berlach et al Sedation and dysphoria were prominent sequelae. An RCT of nabilone in 41 post-operative subjects actually documented exacerbation of pain scores after thrice daily dosing Beaulieu Table 1.
An abstract of a study of 82 cancer patients on nabilone claimed improvement in pain levels after varying periods of follow-up compared to patients treated without this agent Maida However, 17 subjects dropped out, and the study was neither randomized nor controlled, and therefore is not included in Table 1. Part of its analgesic activity may relate to binding to intracellular peroxisome proliferator-activator receptor gamma Liu et al Peak plasma concentrations have generally been attained in 1—2 hours, but with delays up to 4—5 hours is some subjects Karst et al Debate surrounds the degree of psychoactivity associated with the drug Dyson et al Current research is confined to the indication of interstitial cystitis.
CBD ratios reviewed in Russo and Guy , generally approximately 2: Two pharmacokinetic studies on possibly related material have been reported Nadulski et al a ; Nadulski et al b. Both Marinol and Cannador produced reductions in pain scores in long-term follow-up Zajicek et al Cannador was assayed in postherpetic neuralgia in 65 subjects with no observed benefit Ernst et al Table 1 , and in 30 post-operative pain subjects CANPOP without opiates, with slight benefits, but prominent psychoactive sequelae Holdcroft et al Table 1.
It was approved by Health Canada in June for prescription for central neuropathic pain in multiple sclerosis, and in August , it was additionally approved for treatment of cancer pain unresponsive to optimized opioid therapy. Sativex effects commence in 15—40 minutes, an interval that permits symptomatic dose titration.
A very favorable adverse event profile has been observed in over patient years of exposure in over experimental subjects. Patients most often ascertain an individual stable dosage within 7—10 days that provides therapeutic relief without unwanted psychotropic effects often in the range of 8—10 sprays per day. In a Phase II double-blind crossover study of intractable chronic pain Notcutt et al in 24 subjects, visual analogue scales VAS were 5. During that time, there was no escalation of dose indicating an absence of tolerance to the preparation.
Similarly, no withdrawal effects were noted in a subset of patients who voluntarily stopped the medicine abruptly. Upon resumption, benefits resumed at the prior established dosages. In a Phase II double-blind, randomized, placebo-controlled, 5-week study of 56 rheumatoid arthritis patients with Sativex Blake et al , employed nocturnal treatment only to a maximum of 6 sprays per evening In a study of spinal injury pain, NRS of pain were not statistically different from placebo, probably due to the short duration of the trial, but secondary endpoints were clearly positive Table 1.
Finally, in an RCT of intractable lower urinary tract symptoms in MS, accompanying pain in affected patients was prominently alleviated Table 1. Common adverse events AE of Sativex acutely in RCTs have included complaints of bad taste, oral stinging, dry mouth, dizziness, nausea or fatigue, but do not generally necessitate discontinuation, and prove less common over time.
While there have been no head-to-head comparative RCTs of Sativex with other cannabinoid agents, certain contrasts can be drawn. Sativex Rog et al and Marinol Svendsen et al have both been examined in treatment of central neuropathic pain in MS, with comparable results Table 1. However, adverse events were comparable or greater with Marinol than with Sativex employing THC dosages some 2.
Similarly, while Sativex and smoked cannabis have not been employed in the same clinical trial, comparisons of side effect profiles can be made on the basis of SAFEX studies of Sativex for over a year and up to several years in MS and other types of neuropathic pain Russo b ; Wade et al , and government-approved research programs employing standardized herbal cannabis from Canada for chronic pain Lynch et al and the Netherlands for general conditions Janse et al ; Gorter et al over a period of several months or more.
As is evident in Figure 2 Figure 2 , all adverse events are more frequently reported with herbal cannabis, except for nausea and dizziness, both early and usually transiently reported with Sativex see Russo b for additional discussion. Comparison of adverse events AE encountered with long term therapeutic use of herbal cannabis in the Netherlands Janse et al ; Gorter et al and Canada Lynch et al , vs that observed in safety-extension SAFEX studies of Sativex oromucosal spray Russo ; Wade et al Phytocannabinoids are lipid soluble with slow and erratic oral absorption.
While cannabis users claim that the smoking of cannabis allows easy dose titration as a function of rapid onset, high serum levels in a short interval inevitably result. This quick onset is desirable for recreational purposes, wherein intoxication is the ultimate goal, but aside from paroxysmal disorders eg, episodic trigeminal neuralgia or cluster headache attack , such rapid onset of activity is not usually necessary for therapeutic purposes in chronic pain states.
The vast majority of subjects in Sativex clinical trials do not experience psychotropic effects outside of initial dose titration intervals Figure 2 and most often report subjective intoxication levels on visual analogue scales that are indistinguishable from placebo, in the single digits out of Wade et al Thus, it is now longer tenable to claim that psychoactive effects are a necessary prerequisite to symptom relief in the therapeutic setting with a standardized intermediate onset cannabis-based preparation.
Intoxication has remained a persistent issue in Marinol usage Calhoun et al , in contrast. Recent controversies have arisen in relation to non-steroidal anti-inflammatory drugs NSAID , with concerns that COX-1 agents may provoke gastrointestinal ulceration and bleeding, and COX-2 drugs may increase incidents of myocardial infarction and cerebrovascular accidents Fitzgerald ; Topol Frequent questions have been raised as to whether psychoactive drugs may be adequately blinded masked in randomized clinical trials.
Internal review and outside analysis have confirmed that blinding in Sativex spasticity studies has been effective Clark and Altman ; Wright Sativex and its placebo are prepared to appear identical in taste and color. Great public concern attends recreational cannabis usage and risks of dependency.
The addictive potential of a drug is assessed on the basis of five elements: Drug abuse liability DAL is also assessed by examining a drug's rates of abuse and diversion. US Congress placed cannabis in Schedule I of the Controlled Substances Act in , with drugs categorized as addictive, dangerous, possessing severe abuse potential and no recognized medical value.
Marinol was placed in Schedule II, the category for drugs with high abuse potential and liability to produce dependency, but certain recognized medical uses, after its FDA approval in Marinol was reassigned to Schedule III in , a category denoting a lesser potential for abuse or lower dependency risk after documentation that little abuse or diversion Calhoun et al had occurred.
Nabilone was placed and has remained in Schedule II since The degree to which a drug is reinforcing is determined partly by the by the rate of its delivery to the brain Samaha and Robinson Sativex has effect onset in 15—40 minutes, peaking in a few hours, quite a bit slower than drugs of high abuse potential.
It has been claimed that inclusion of CBD diminishes psychoactive effects of THC, and may lower potential drug abuse liability of the preparation see Russo b for discussion. Prior studies from Sativex clinical trials do not support the presence reinforcement or euphoria as problems in administration Wade et al Certain facets of acute cannabinoid exposure, including tachycardia, hypothermia, orthostatic hypotension, dry mouth, ocular injection, intraocular pressure decreases, etc.
No dose tolerance to the therapeutic effects of Sativex has been observed in clinical trials in over patient-years of administration. Additionally, therapeutic efficacy has been sustained for several years in a wide variety of symptoms; SAFEX studies in MS and peripheral neuropathic pain, confirm that Sativex doses remain stable or even decreased after prolonged usage Wade et al , with maintenance of therapeutic benefit and even continued improvement.
Debate continues as to the existence of a clinically significant cannabis withdrawal syndrome with proponents Budney et al , and questioners Smith While symptoms recurred after 7—10 days of abstinence from Sativex, prior levels of symptom control were readily re-established upon re-titration of the agent Wade et al Overall, Sativex appears to pose less risk of dependency than smoked cannabis based on its slower onset, lower dosage utilized in therapy, almost total absence of intoxication in regular usage, and minimal withdrawal symptomatology even after chronic administration.
No known abuse or diversion incidents have been reported with Sativex to date as of November Cognitive effects of cannabis have been reviewed Russo et al ; Fride and Russo , but less study has occurred in therapeutic contexts. Effects of chronic heavy recreational cannabis usage on memory abate without sequelae after a few weeks of abstinence Pope et al Studies of components of the Halstead-Reitan battery with Sativex in neuropathic pain with allodynia have revealed no changes vs placebo Nurmikko et al , and in central neuropathic pain in MS Rog et al , 4 of 5 tests showed no significant differences.
While the Selective Reminding Test did not change significantly on Sativex, placebo patients displayed unexpected improvement. Slight improvements were observed in Hospital Anxiety and Depression Scales depression and anxiety scores were noted with Sativex in MS patients with central neuropathic pain Rog et al , although not quite statistically significant.
No long-term mood disorders have been associated with Sativex administration. Debate continues with regard to the relationship between cannabis usage and schizophrenia reviewed Fride and Russo An etiological relationship is not supported by epidemiological data Degenhardt et al , but if present, should bear relation to dose and length of high exposure.
It is likely that lower serum levels of Sativex in therapeutic usage, in conjunction with anti-psychotic properties of CBD Zuardi and Guimaraes , would minimize risks. Children and adolescents have been excluded from Sativex RCTs to date. SAFEX studies of Sativex have yielded few incidents of thought disorder, paranoia or related complaints. Adverse effects of cannabinoids on immune function have been observed in experimental animals at doses 50— times the psychoactive level Cabral In four patients using herbal cannabis therapeutically for over 20 years, no abnormalities were observed in leukocyte, CD4 or CD8 cell counts Russo et al Investigation of MS patients on Cannador revealed no major immune changes Katona et al , and similarly, none occurred with smoked cannabis in a short-term study of HIV patients Abrams et al Hematological measures have been normal in all Sativex RCTs without clinical signs of immune dysfunction.
Concerns are frequently noted with new drug-drug interactions, but few have resulted in Sativex RCTs despite its adjunctive use with opiates, many other psychoactive analgesic, antidepressant and anticonvulsant drugs Russo a , possibly due to CBD ability to counteract sedative effects of THC Nicholson et al Thus, Sativex should be safe to use in conjunction with other drugs metabolized via this pathway.
The Sativex product monograph in Canada http: Given that THC is the most active component affecting such abilities, and the low serum levels produced in Sativex therapy vide supra , it would be logical that that patients may be able to safely engage in such activities after early dose titration and according to individual circumstances, much as suggested for oral dronabinol.
This is particularly the case in view of a report by an expert panel Grotenhermen et al that comprehensively analyzed cannabinoids and driving. Prior studies document that 4 rapid oromucosal sprays of Sativex greater than the average single dose employed in therapy produced serum levels well below this threshold Russo b.
Sativex is now well established as a cannabinoid agent with minimal psychotropic effect. These include anti-emetic effects, well established with THC, but additionally demonstrated for CBD Pertwee , the ability of THC and CBD to produce apoptosis in malignant cells and inhibit cancer-induced angiogenesis Kogan ; Ligresti et al , as well as the neuroprotective antioxidant properties of the two substances Hampson et al , and improvements in symptomatic insomnia Russo et al The degree to which cannabinoid analgesics will be adopted into adjunctive pain management practices currently remains to be determined.
Given their multi-modality effects upon various nociceptive pathways, their adjunctive side benefits, the efficacy and safety profiles to date of specific preparations in advanced clinical trials, and the complementary mechanisms and advantages of their combination with opioid therapy, the future for cannabinoid therapeutics appears very bright, indeed.
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Abstract 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. Introduction Chronic pain represents an emerging public health issue of massive proportions, particularly in view of aging populations in industrialized nations.
Cannabinoids and analgesic mechanisms Cannabinoids are divided into three groups. Open in a separate window. Molecular structures of four cannabinoids employed in pain treatment.
Available cannabinoid analgesic agents and those in development Very few randomized controlled trials RCTs have been conducted using smoked cannabis Campbell et al despite many anecdotal claims Grinspoon and Bakalar Table 1 Results RCTs of cannabinoids in treatment of pain syndromes. Practical issues with cannabinoid medicines Phytocannabinoids are lipid soluble with slow and erratic oral absorption. Broad experience with pain sparks search for relief [online] Short-term effects of cannabinoids in patients with HIV-1 infection.
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Cannabinoids in the management of difficult to treat pain
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