Model‐Based Analysis of Cannabidiol Dose‐Exposure Relationship and Bioavailability

Advances and Challenges in Modeling Cannabidiol Pharmacokinetics and Hepatotoxicity

Cannabidiol (CBD) is a pharmacologically active metabolite of cannabis that is US Food and Drug Administration approved to treat seizures associated with Lennox-Gastaut syndrome, Dravet syndrome, and tuberous sclerosis complex in children aged 1 year and older. During clinical trials, CBD caused dose-dependent hepatocellular toxicity at therapeutic doses. The risk for toxicity was increased in patients taking valproate, another hepatotoxic antiepileptic drug, through an unknown mechanism. With the growing popularity of CBD in the consumer market, an improved understanding of the safety risks associated with CBD is needed to ensure public health. This review details current efforts to describe CBD pharmacokinetics and mechanisms of hepatotoxicity using both pharmacokinetic models and in vitro models of the liver. In addition, current evidence and knowledge gaps related to intracellular mechanisms of CBD-induced hepatotoxicity are described. The authors propose future directions that combine systems-based models with markers of CBD-induced hepatotoxicity to understand how CBD pharmacokinetics may influence the adverse effect profile and risk of liver injury for those taking CBD. SIGNIFICANCE STATEMENT: This review describes current pharmacokinetic modeling approaches to capture the metabolic clearance and safety profile of cannabidiol (CBD). CBD is an increasingly popular natural product and US Food and Drug Administration-approved antiepileptic drug known to cause clinically significant enzyme-mediated drug interactions and hepatotoxicity at therapeutic doses. CBD metabolism, pharmacokinetics, and putative mechanisms of CBD-induced liver injury are summarized from available preclinical data to inform future modeling efforts for understanding CBD toxicity.

Cannabidiol Bioavailability Is Nonmonotonic with a Long Terminal Elimination Half-Life: A Pharmacokinetic Modeling-Based Analysis

Background: Oral and inhalation-based cannabidiol (CBD) administration has been clinically evaluated for various therapeutic indications, alongside widespread off-label use. However, the long-term exposure kinetics and varied bioavailability have not been fully characterized. Methods: Human CBD plasma concentration-time profiles from six studies evaluating the oral administration of Epidiolex® and three studies evaluating inhalation-based delivery were obtained. A four-compartment pharmacokinetic (PK) model with Weibull-based oral absorption kinetics was employed to describe the long-term PKs of CBD. Furthermore, a Cedergreen-Ritz-Streibig model was applied to evaluate nonmonotonic oral bioavailability. Results: CBD was extensively distributed into tissue compartments with varied kinetics resulting in a long plasma terminal elimination half-life of >134 h in humans. For once-a-day oral dosing, the plasma trough concentrations require >70 days to reach a steady state. The oral bioavailability of CBD for different doses administered in fasted state follows a nonmonotonic pattern with an inverted U-shaped profile. Oral administration of CBD under fed state or subjects with hepatic impairment yields higher oral bioavailability with varied exposure. In contrast, inhalation-based delivery of CBD, while delivering a similar systemic delivered dose compared with oral dosing due to high device losses, bypasses first-pass metabolism and can be efficient. Conclusion: CBD PKs vary across different doses due to nonmonotonic oral bioavailability, and inhalation-based delivery could minimize such variability in humans. The delayed attainment of steady state and prolonged terminal half-life, resulting from differential but extensive tissue distribution, needs to be considered when dosing CBD in the long term. These fundamental findings are critical for establishing dose-exposure relationship for further clinical evaluation of novel CBD-based therapies.

Strategies to Improve Cannabidiol Bioavailability and Drug Delivery

The poor physicochemical properties of cannabidiol (CBD) hamper its clinical development. The aim of this review was to examine the literature to identify novel oral products and delivery strategies for CBD, while assessing their clinical implications and translatability. Evaluation of the published literature revealed that oral CBD strategies are primarily focused on lipid-based and emulsion solutions or encapsulations, which improve the overall pharmacokinetics (PK) of CBD. Some emulsion formulations demonstrate more rapid systemic delivery. Variability in the PK effects of different oral CBD products is apparent across species. Several novel administration routes exist for CBD delivery that may offer promise for specific indications. For example, intranasal administration and inhalation allow quick delivery of CBD to the plasma and the brain, whereas transdermal and transmucosal administration routes deliver CBD systemically more slowly. There are limited but promising data on novel delivery routes such as intramuscular and subcutaneous. Very limited data show that CBD is generally well distributed across tissues and that some CBD products enable increased delivery of CBD to different brain regions. However, evidence is limited regarding whether changes in CBD PK profiles and tissue distribution equate to superior therapeutic efficacy across indications and whether specific CBD products might be suited to particular indications.

Subtype-specific modulation of human KV 7 channels by the anticonvulsant cannabidiol through a lipid-exposed pore-domain site

BACKGROUND AND PURPOSE

Cannabidiol (CBD) is used clinically as an anticonvulsant. Its precise mechanism of action has remained unclear. CBD was recently demonstrated to enhance the activity of the neuronal KV 7.2/7.3 channel, which may be one important contributor to CBD anticonvulsant effect. Curiously, CBD inhibits the closely related cardiac KV 7.1/KCNE1 channel. Whether and how CBD affects other KV 7 subtypes remains uninvestigated and the CBD interaction sites mediating these diverse effects remain unknown.

EXPERIMENTAL APPROACH

Here, we used electrophysiology, molecular dynamics simulations, molecular docking and site-directed mutagenesis to address these questions.

KEY RESULTS

We found that CBD modulates the activity of all human KV 7 subtypes and that the effects are subtype dependent. CBD enhanced the activity of KV 7.2-7.5 subtypes, seen as a V50 shift towards more negative voltages or increased maximum conductance. In contrast, CBD inhibited the KV 7.1 and KV 7.1/KCNE1 channels, seen as a V50 shift towards more positive voltages and reduced conductance. In KV 7.2 and KV 7.4, we propose a CBD interaction site at the subunit interface in the pore domain that overlaps with the interaction site of other compounds, notably the anticonvulsant retigabine. However, CBD relies on other residues for its effects than the conserved tryptophan that is critical for retigabine effects. We propose a similar, though not identical CBD site in KV 7.1, with a non-conserved phenylalanine being important.

CONCLUSIONS AND IMPLICATIONS

We identify novel targets of CBD, contributing to a better understanding of CBD clinical effects and provide mechanistic insights into how CBD modulates different KV 7 subtypes.

Pharmacokinetics and oral bioavailability of cannabidiol in horses after intravenous and oral administration with oil and micellar formulations

BACKGROUND

Intravenous pharmacokinetics and oral bioavailability of cannabidiol (CBD) with different formulations have not been investigated in horses and may represent a starting point for clinical studies.

OBJECTIVES

To describe pharmacokinetics after intravenous and oral administrations with oil and micellar formulations and simulate different treatments.

STUDY DESIGN

Single intravenous experiment and two-way randomised oral experiments, Latin-square design.

METHODS

Eight healthy horses received intravenous CBD at 1.00 mg/kg dose, oral CBD in sesame oil and in micellar formulation, both at 10.00 mg/kg. Concentrations were measured using LC-MS/MS and fitted by nonlinear mixed effect modelling. Parameters obtained were used to simulate single and multiple treatments at steady state.

RESULTS

Intravenous and oral concentrations were simultaneously fitted using a three-compartment model. Final estimates indicate that CBD has a volume of distribution of 36 L/kg associated with a systemic clearance of 1.46 L/h/kg and half-lives ranged between 24 and 34 h. Oral bioavailability was close to 14% for both oral administrations. Simulated dose regimen of CBD every 12 and 24 h predicted similar percentages to reach effective plasma concentration with both oral formulation at 10.00 mg/kg.

MAIN LIMITATIONS

A small horse population was used (8 horses per trial).

CONCLUSIONS AND CLINICAL IMPORTANCE

Oral bioavailability was low at the doses studied but fell within the range described for horse and other species. CBD had a high steady-state volume of distribution, a high clearance and long half-lives. No adverse reactions were detected at any dose or route. The micellar formulation showed a faster absorption and higher concentration peak, while the oil formulation presented lower levels, but more maintained over time. Simulations predicted that both could be useful in multiple oral dose treatments. These results indicated that CBD could be of interest, but further studies are needed to evaluate its clinical use in horses.

Population Pharmacokinetics of Oral-Based Administration of Cannabidiol in Healthy Adults: Implications for Drug Development

Background and Objectives: Cannabidiol (CBD) is increasingly being studied as a therapeutic option for a range of health conditions; however, the pharmacokinetics of CBD is not well understood. This study characterized CBD pharmacokinetics in healthy adults using a population pharmacokinetic approach, informing drug development of oral-based dose forms of CBD. Materials and Methods: CBD concentration-time data were obtained from a phase I, randomized, open-label, four-way crossover study (n=12) and modeled using Phoenix NLME. Monte Carlo simulations were conducted to estimate CBD exposure with chronic dosing as intended for clinical use (50 mg b.i.d.). Results: A three-compartment pharmacokinetic model with a chain of absorption transit compartments and first-order elimination most adequately described CBD pharmacokinetics. Substantial variability in population pharmacokinetic parameters was identified (up to 60%CV), which could not be accounted for by any covariates. Simulations indicated a 3.6-fold difference in drug exposure at steady state with multiple dosing (AUCτ 95% prediction interval: 65.5-138 ng·h/mL), and variability in the time to reach steady state, which was predicted to be up to ∼3 weeks in some individuals (95% prediction interval: 18.6-297 h). Conclusions: The findings of this study have important implications for drug development. The lack of a clear dose-response relationship, due to large pharmacokinetic variability, indicates that a one-size-fits-all approach to CBD dosing may not be feasible, at least with current dosing approaches. Furthermore, an extended time to reach steady state means that the full effect of a selected dose level is not truly observed for some time and requires careful consideration in trial design.

Cannabidiol plasma determination and pharmacokinetics conducted at beginning, middle and end of long-term supplementation of a broad-spectrum hemp oil to healthy adult dogs

Introduction

Veterinary hemp products containing cannabidiol (CBD) and negligible psychoactive (THC) have increased popularity since hemp (with <0.3% THC) was removed from schedule 1 substances under the Controlled Substances Act in 2018. This was accompanied by increased CBD research, mostly on the short-term safety and efficacy for inflammatory and neurological conditions. It is imperative to understand how CBD is metabolized or accumulated in the body long-term, thus the goal of the present work was to determine monthly plasma CBD concentrations, as well as changes in pharmacokinetic (PK) parameters in chronically dosed dogs.

Methods

The study was a masked, placebo-controlled, randomized design. Six adult beagles were assigned to placebo, 5 and 10 mg/kg/day CBD treatment groups. Dogs received oral oil treatment once daily for 36 weeks. Blood was collected once every 4 weeks pre- and postprandially for CBD plasma determination (at 0 and 2 h). Pharmacokinetics were conducted at 0, 18 and 36 weeks. Pharmacokinetics and monthly CBD plasma data of dogs who received CBD were analyzed as repeated measures over time using a mixed model, with significance at α = 0.05.

Results

Average plasma CBD at 5 and 10 mg/kg were 97.3 ng/mL and 236.8 ng/mL pre-prandial, 341 ng/mL and 1,068 ng/mL postprandial, respectively. PK parameters suggested CBD accumulation over time, with significant increases in Cmax and AUC at both the 18 and 36-week timepoints. Cmax and AUC were dose proportional. Half-life demonstrated large inter-individual variations and increased (p < 0.05) at weeks 18 and 36 compared to baseline. Volume of distribution was not affected by time or treatment, while MRT increased, and clearance decreased over time (p < 0.05).

Conclusions and clinical importance

Chronic administration of CBD to healthy adult dogs led to a dose-proportional accumulation in the body for 36 weeks, which was confirmed by an increased half-life, total exposure, mean residence time and plasma peak. Our data also suggests that CBD plasma levels may have less daily variation if administered twice daily.

Cannabidiol Oil Ingested as Sublingual Drops or Within Gelatin Capsules Shows Similar Pharmacokinetic Profiles in Healthy Males

Introduction: Cannabidiol (CBD) is a nonintoxicating phytocannabinoid used in clinical treatments and sold widely in consumer products. CBD products may be designed for sublingual or oral delivery, but it is unclear whether either is advantageous for CBD absorption. This study compared CBD pharmacokinetics after providing CBD oil as sublingual drops and within orally ingested gelatin capsules, at a dose relevant to consumer products. Materials and Methods: Eight males completed three conditions in a participant-blinded, randomized crossover design. Participants received the following combinations of placebo and CBD-containing (69 mg/mL) hemp oil in capsules and as sublingual drops: placebo capsules/placebo drops (Placebo), CBD capsules/placebo drops (CBD-Caps), and placebo capsules/CBD drops (CBD-Drops). Blood samples, blood pressure, and subjective scales were obtained/completed hourly for 6 h and at 24 h. Discussion: Plasma CBD concentrations were not different between CBD-Caps and CBD-Drops (interaction effect p=0.76). Peak CBD concentration (28.0±15.6 vs. 24.0±22.2 ng/mL), time of peak CBD concentration (4±1 vs. 4±2 h), and area under the concentration curve (45.3±20.3 vs. 41.8±23.3 ng/mL·6 h) were not different between conditions (p≥0.25). Cardiometabolic outcomes (plasma glucose/triacylglycerol, heart rate, blood pressure), liver function (plasma alanine aminotransferase/aspartate aminotransferase), kidney function (plasma creatinine), and subjective feelings/symptoms were not different between conditions (p≥0.07). Conclusions: Plasma CBD profiles were comparable between CBD-Caps and CBD-Drops, suggesting that there were not meaningful differences in routes of CBD absorption between conditions. This implies that CBD oil delivered sublingually is swallowed before oral mucosal CBD absorption occurs, which may have implications for research design, CBD product design, and consumer product choice.

The Mechanism of Cannabichromene and Cannabidiol Alone Versus in Combination in the Alleviation of Arthritis-Related Inflammation

BACKGROUND

Patients suffering from arthritis have limited treatment options for nonoperative management. In search of pain relief, patients have been taking over-the-counter cannabinoids. Cannabidiol (CBD) and cannabichromene (CBC) are minor cannabinoids with reported analgesic and anti-inflammatory properties and have been implicated as potential therapeutics for arthritis-related pain. To this end, we utilized a murine model to investigate the effectiveness of and mechanism by which CBC alone, CBD alone, or CBD and CBC in combination may provide a reduction in arthritis-associated inflammation.

METHODS

Forty-eight mice were included in the study, which were separated into 4 groups: control group (n = 12), treatment with CBD alone (n = 12), treatment with CBC alone (n = 12), and treatment with CBD + CBC (n = 12). We induced inflammation in each mouse utilizing the collagen-induced arthritis model. At scheduled timepoints, mice were clinically assessed for weight gain, swelling, and arthritis severity. In addition, inflammation-associated serum cytokine levels were analyzed for each animal.

RESULTS

Thirty-five of 48 mice survived the duration of the study resulting in the following group numbers: control group (n = 8), treatment with CBD alone (n = 9), treatment with CBC alone (n = 9), and treatment with CBD + CBC (n = 9). Animals treated with CBC and CBD + CBC showed significant weight gain between 3 and 5 weeks. Irrespective of treatment, regression analysis comparing all cytokine measurement and physical outcomes found a significant positive correlation between levels of 5 individual cytokines and both arthritis scores and swelling. Animals treated with CBD + CBC showed a significant decrease in swelling between 3 and 5 weeks compared with the control group. Cannabinoid treatment selectively affected the gene expression of eotaxin and lipopolysaccharide-induced CXC chemokine with combined treatment of CBC + CBD.

CONCLUSION

Treatment with cannabinoids resulted in decreased clinical markers of inflammation. Further, the anti-inflammatory effect of CBC and CBD in conjunction was associated with a greater anti-inflammatory effect than either minor cannabinoid alone. Future work will elucidate the possibility of synergistic or entourage effects of minor cannabinoids used in combination for the treatment of arthritis-related pain and inflammation.

Verifying in vitro-determined enzyme contributions to cannabidiol clearance for exposure predictions in human through physiologically-based pharmacokinetic modeling

Cannabidiol (CBD) is approved for treatment of seizures associated with two forms of epilepsy that become apparent in infancy or early childhood. To consider an adult physiologically-based pharmacokinetic (PBPK) model for pediatric scaling, we assessed in vitro-derived cytochrome P450 (CYP) and uridine 5'-diphospho-glucuronosyltransferase (UGT) enzyme contributions to CBD clearance in human. An i.v. PBPK model was constructed using CBD physicochemical properties and knowledge of disposition. The i.v. datasets were used for model building and evaluation. Oral PBPK models for CBD administered in fasted and fed states were developed using single dose oral datasets and parameters optimized from the i.v. model and evaluated with multiple dose datasets. Relative contributions of CBD metabolizing enzymes were partitioned according to in vitro studies. Clinical drug-drug interaction (DDI) studies were simulated using CBD fed state, itraconazole, fluconazole, and rifampicin PBPK models. Linear mixed effect modeling was used to estimate area under the concentration-time curve from zero to infinity (AUC0-∞ ) perpetrator + CBD versus CBD alone. The i.v. and oral datasets used in model evaluation produced acceptable average fold error (AFE) of 1.28 and absolute AFE of 1.65. Relative contributions of drug-metabolizing enzymes to CBD clearance were proposed from in vitro data: UGT1A7 4%, UGT1A9 16%, UGT2B7 10%, CYP3A4 38%, CYP2C19 21%, and CYP2C9 11%. The simulated DDI studies using the in vitro-derived values produced AUC0-∞ treatment ratios comparable to observed: itraconazole 1.24 versus 1.07, fluconazole 1.45 versus 1.22, and rifampicin 0.49 versus 0.69. The constructed CBD PBPK models can predict adult exposures and have potential for use in pediatrics where exposure estimates are limited.

The effect of tetrahydrocannabinol:cannabidiol oromucosal spray on cognition: a systematic review

PURPOSE

Previous studies have shown that tetrahydrocannabinol (THC), the main psychoactive component of cannabis, can impair cognitive abilities. There is also some evidence that cannabidiol (CBD), the most abundant non-intoxicating constituent of cannabis, can attenuate these effects. The purpose of this study was to investigate the effects of THC:CBD oromucosal spray (with equal parts THC and CBD) on cognition compared with control conditions in human studies.

METHODS

A systematic literature search was performed on four major bibliographic databases. Studies were included in the present review if they evaluated the cognitive effects of THC:CBD oromucosal spray compared with a control condition.

RESULTS

Ten studies were identified (7 on patients with multiple sclerosis, 1 on those with Huntington, and 2 on healthy volunteers) with 510 participants in total. There was considerable heterogeneity among the studies in terms of dose and duration of administration. All studies have used an equal or nearly equal dose of THC and CBD.

CONCLUSIONS

Although the results across studies were somewhat inconsistent, most evidence revealed that there is no significant difference between THC:CBD oromucosal spray and control treatments in terms of cognitive outcomes. However, more trials are needed with longer follow-up periods, and dose considerations, particularly comparing lower and higher doses of the spray.

Non-psychotropic phytocannabinoid interactions with voltage-gated sodium channels: An update on cannabidiol and cannabigerol

Phytocannabinoids, found in the plant, Cannabis sativa, are an important class of natural compounds with physiological effects. These compounds can be generally divided into two classes: psychoactive and non-psychoactive. Those which do not impart psychoactivity are assumed to predominantly function via endocannabinoid receptor (CB) -independent pathways and molecular targets, including other receptors and ion channels. Among these targets, the voltage-gated sodium (Nav) channels are particularly interesting due to their well-established role in electrical signalling in the nervous system. The interactions between the main non-psychoactive phytocannabinoid, cannabidiol (CBD), and Nav channels were studied in detail. In addition to CBD, cannabigerol (CBG), is another non-psychoactive molecule implicated as a potential therapeutic for several conditions, including pain via interactions with Nav channels. In this mini review, we provide an update on the interactions of Nav channels with CBD and CBG.

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

ABSTRACT

Opioids in general and remifentanil in particular can induce hyperalgesia. Preclinical data suggest that cannabidiol might have the capacity to reduce opioid-induced hyperalgesia (OIH). Thus, we investigated the effect of oral cannabidiol on OIH in healthy volunteers using an established pain model. Twenty-four healthy participants were included in this randomized, double-blinded, crossover study and received either a 1600-mg single-dose oral cannabidiol or placebo. Hyperalgesia, allodynia, and pain were induced by intracutaneous electrical stimulation. To provoke OIH, participants recieved an infusion of 0.1 µg/kg/min remifentanil over a time frame of 30 minutes, starting 100 minutes after oral cannabidiol ingestion. The primary outcome was the area of hyperalgesia (in square centimetres) up to 60 minutes after remifentanil administration. The area of allodynia (in square centimetres) and pain (numeric rating scale) were also assessed.Cannabidiol had no significant effect on hyperalgesia, allodynia, or pain at any time point of measurement compared with placebo. The area of hyperalgesia after remifentanil administration significantly increased compared with baseline (17.0 cm 2 [8.1-28.7] vs 25.3 cm 2 [15.1-39.6]; P = 0.013). Mean cannabidiol blood levels were 4.1 ± 3.0 µg/L (mean ± SD) at 130 minutes after ingestion and were 8.2 μg/L ± 6.9 µg/L (mean ± SD) at 200 minutes. Cannabidiol was well tolerated. We conclude that a high single-oral dose of 1600-mg cannabidiol is not effective in reducing OIH. Before excluding an effect of cannabidiol on OIH, research should focus on drug formulations enabling higher cannabidiol concentrations.

Pharmacokinetic Profile of ∆9-Tetrahydrocannabinol, Cannabidiol and Metabolites in Blood following Vaporization and Oral Ingestion of Cannabidiol Products

There is limited data on the comparative pharmacokinetics of cannabidiol (CBD) across oral and vaporized formulations. This within-subject, double-blind, double-dummy, placebo-controlled laboratory study analyzed the pharmacokinetic profile of CBD, ∆9-tetrahydrocannabinol (∆9-THC) and related metabolites in blood and oral fluid (OF) after participants (n = 18) administered 100 mg of CBD in each of the following formulations: (1) oral CBD, (2) vaporized CBD and (3) vaporized CBD-dominant cannabis containing 10.5% CBD and 0.39% ∆9-THC (3.7 mg); all participants also completed a placebo condition. Oral CBD was administered in three formulations: (1) encapsulated CBD, (2) CBD suspended in pharmacy-grade syrup and (3) Epidiolex, allowing for pharmacokinetic comparisons across oral formulations (n = 6 per condition). An optional fifth experimental condition was completed for six participants in which they fasted from all food for 12 h prior to oral ingestion of 100 mg of CBD. Blood and OF samples were collected immediately before and for 57-58 h after each drug administration. Immunoassay screening and LC-MS-MS confirmatory tests were performed, the limit of quantitation was 0.5 ng/mL for ∆9-THC and 1 ng/mL for CBD. The mean Cmax and range of CBD blood concentrations for each product were as follows: vaporized CBD-dominant cannabis, 171.1 ng/mL, 40.0-665.0 ng/mL, vaporized CBD 104.6 ng/mL, 19.0-312.0 ng/mL and oral CBD, 13.7 ng/mL, 0.0-50.0 ng/mL. Of the three oral formulations, Epidiolex produced the greatest peak concentration of CBD (20.5 ng/mL, 8.0-37.0 ng/mL) relative to the capsule (17.8 ng/mL, 2.0-50.0 ng/mL) and syrup (2.8 ng/mL, 0-7.0 ng/mL). ∆9-THC was detected in the blood of 12/18 participants after vaporized CBD-dominant cannabis use, but neither ∆9-THC nor its metabolite THC-COOH were detected in the blood of any participants after vaporized or oral CBD-only administration. These data demonstrate that different oral and vaporized formulations produce substantial variability in the pharmacokinetics of CBD and that CBD alone is unlikely to convert to ∆9-THC or produce positive drug tests for ∆9-THC or its metabolite.

Strategies for enhancing the oral bioavailability of cannabinoids

INTRODUCTION

Oral administration of cannabinoids is a convenient route of administration in many cases. To enhance the poor and variable bioavailability of cannabinoids, selected strategies utilizing proper delivery systems have been designed. Low solubility in the GI aqueous media is the first and most critical barrier. Thereafter, cannabinoids can reach the systemic blood circulation via the portal vein that is associated with significant hepatic first pass metabolism (FPM) or bypass it via lymphatic absorption.

AREAS COVERED

The solubility obstacle of cannabinoids is mainly addressed with lipid-based formulations such as self-nanoemulsifying drug delivery systems (SNEDDS). Certain lipids are used to overcome the solubility issue. Surfactants and other additives in the formulation have additional impact on several barriers, including dictating the degree of lymphatic bioavailability and hepatic FPM. Gastro-retentive formulation is also plausible.

EXPERT OPINION

Comparison of the role of the same SNEDDS formulation, cyclosporine vs. cannabinoids, when used to elevate the oral bioavailability of different compounds, is presented. It illustrates some similarities and major mechanistic differences obtained by the same SNEDDS. Thus, the different influence over the absorption pathway illuminates the importance of understanding the absorption mechanism and its barriers to properly select appropriate strategies to achieve enhanced oral bioavailability.

Lipid-Drug Conjugates and Nanoparticles for the Cutaneous Delivery of Cannabidiol

Lipid nanoparticles are currently used to deliver drugs to specific sites in the body, known as targeted therapy. Conjugates of lipids and drugs to produce drug-enriched phospholipid micelles have been proposed to increase the lipophilic character of drugs to overcome biological barriers. However, their applicability at the topical level is still minimal. Phospholipid micelles are amphiphilic colloidal systems of nanometric dimensions, composed of a lipophilic nucleus and a hydrophilic outer surface. They are currently used successfully as pharmaceutical vehicles for poorly water-soluble drugs. These micelles have high in vitro and in vivo stability and high biocompatibility. This review discusses the use of lipid-drug conjugates as biocompatible carriers for cutaneous application. This work provides a metadata analysis of publications concerning the conjugation of cannabidiol with lipids as a suitable approach and as a new delivery system for this drug.

Drug-drug interaction between cannabidiol and phenobarbital in healthy dogs

OBJECTIVE

To assess drug-drug interactions between cannabidiol (CBD) and phenobarbital (PB) when simultaneously administered to healthy dogs.

ANIMALS

9 healthy, purpose bred Beagles.

PROCEDURES

A 3-phase prospective, randomized pharmacokinetic (PK) interaction study of CBD and PB was performed as follows: phase 1, CBD PK determination and evaluation of CBD tolerability by 3 single-dose CBD (5 mg/kg, 10 mg/kg, and 20 mg/kg) protocols followed by 2-week CBD dosing; phase 2, a single-dose, 3-way, crossover PK study of CBD (10 mg/kg), PB (4 mg/kg), or CBD (10 mg/kg) administration plus PB (4 mg/kg); and phase 3, evaluation of chronic PB (4 mg/kg, q 30 d) administration followed by single-dose CBD (10 mg/kg) PK study.

RESULTS

Although there were variations in CBD PK variables in dogs receiving CBD alone or in conjunction with PB, significance differences in CBD PK variables were not found. No significant difference was observed in PB PK variables of dogs receiving PB alone or with CBD. During chronic CBD administration, mild gastrointestinal signs were observed in 5 dogs. At daily CBD doses of 10 to 20 mg/kg/d, hypoxia was observed in 5 dogs and increased serum alkaline phosphatase (ALP) activities (range, 301 to 978 U/L) was observed in 4 dogs. A significant increase in ALP activity was observed with chronic administration of CBD during phase 1 between day 0 and day 14.

CONCLUSIONS AND CLINICAL RELEVANCE

No significant PK interactions were found between CBD and PB. Dose escalation of CBD or adjustment of PB in dogs is not recommended on the basis of findings of this study.

Improved Bioavailability with Dry Powder Cannabidiol Inhalation: A Phase 1 Clinical Study

Oral cannabidiol (CBD) is approved by the Food and Drug Administration (FDA) to treat patients with Dravet and Lennox-Gastaut syndromes, and tuberous sclerosis complex. The therapeutic potential of oral CBD formulations is limited by extensive first-pass hepatic metabolism. Following oral administration, the inactive metabolite blood concentration is ∼40-fold higher than CBD. Inhalation bypasses the pharmacokinetic (PK) variability attributed to irregular gastrointestinal absorption and first-pass hepatic metabolism and may efficiently deliver CBD into systemic circulation. This phase 1 study compared the PK of a dry-powder inhaler (DPI) CBD formulation (10 mg; excipient containing 2.1 mg CBD) with an oral CBD solution (Epidiolex®, 50 mg) in healthy participants. Following a single dose of Epidiolex or DPI CBD (n=10 PK evaluable participants each), the maximum CBD concentration for the inhaled powder was 71-fold higher than that of Epidiolex while administering 24-fold less CBD. The mean time to reach maximum concentration was 3.8 minutes for the DPI CBD formulation compared with 122 minutes for Epidiolex. Both Epidiolex and DPI CBD were generally safe and well-tolerated. These data indicate that DPI CBD provided more rapid onset and increased bioavailability than oral CBD and support further investigations on the use of DPI CBD for acute indications.

The Effects of Cannabinoids on Pro- and Anti-Inflammatory Cytokines: A Systematic Review of In Vivo Studies

Introduction: Some cannabinoids have been identified as anti-inflammatory agents; however, their potential therapeutic or prophylactic applications remain controversial. The aim of this systematic review was to provide a timely and comprehensive insight into cannabinoid-mediated pro- and anti-inflammatory cytokine responses in preclinical in vivo studies. Methods and Materials: A systematic search was conducted using PubMed, Web of Science, EMBASE, and Scopus. Eligible studies where cannabinoids had been evaluated for their effect on inflammation in animal models were included in the analysis. Data were extracted from 26 of 4247 eligible full text articles, and risk of bias was assessed using the SYstematic Review Center for Laboratory animal Experimentation (SYRCLE) tool. Studies examined cannabidiol (CBD; n=20); cannabigerol (CBG; n=1); delta 9-tetrahydrocannabinol (THC; n=2); THC and CBD separately (n=1); and THC and CBD in combination (n=2). Results: Tumor necrosis factor alpha, interleukin (IL)-1β, IL-6, and interferon gamma were the most commonly studied pro-inflammatory cytokines and their levels were consistently reduced after treatment with CBD, CBG, or CBD+THC, but not with THC alone. The association between cannabinoid-induced anti-inflammatory response and disease severity was examined. In 22 studies where CBD, CBG, or CBD in combination with THC were administered, a reduction in the levels of at least one inflammatory cytokine was observed, and in 24 studies, some improvements in disease or disability were apparent. THC alone did not reduce pro-inflammatory cytokine levels (n=3), but resulted in improvements in neuropathic pain in one study. Conclusions: This review shows that CBD, CBG, and CBD+THC combination exert a predominantly anti-inflammatory effect in vivo, whereas THC alone does not reduce pro-inflammatory or increase anti-inflammatory cytokines. It is anticipated that this information could be used to inform human clinical trials of cannabinoids, focusing on CBD and CBG to reduce inflammation across a range of pathophysiological processes.

Toxicological properties of Δ9-tetrahydrocannabinol and cannabidiol

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

Cannabidiol and Sodium Channel Pharmacology: General Overview, Mechanism, and Clinical Implications

Voltage-gated sodium (Nav) channels initiate action potentials in excitable tissues. Altering these channels' function can lead to many pathophysiological conditions. Nav channels are composed of several functional and structural domains that could be targeted pharmacologically as potential therapeutic means against various neurological conditions. Mutations in Nav channels have been suggested to underlie various clinical syndromes in different tissues and in association with conditions ranging from epileptic to muscular problems. Treating those mutations that increase the excitability of Nav channels requires inhibitors that could effectively reduce channel firing. The main non-psychotropic constituent of the cannabis plant, cannabidiol (CBD), has recently gained interest as a viable compound to treat some of the conditions that are associated with Nav malfunctions. In this review, we discuss an overview of Nav channels followed by an in-depth description of the interactions of CBD and Nav channels. We conclude with some clinical implications of CBD use against Nav hyperexcitability based on a series of preclinical studies published to date, with a focus on Nav/CBD interactions.

Emulsion, hydrogel and emulgel systems and novel applications in cannabinoid delivery: a review

Emulsions, hydrogels and emulgels have attracted a high interest as tools for the delivery of poorly soluble hydrophobic nutraceuticals by enhancing their stability and bioavailability. This review provides an overview of these delivery systems, their unique qualities and their interactions with the human gastrointestinal system. The modulation of the various delivery systems to enhance the bioavailability and modify the release profile of bioactive encapsulates is highlighted. The application of the delivery systems in the delivery of cannabinoids is also discussed. With the recent increase of cannabis legalization across North America, there is much interest in developing cannabis edibles which can provide a consistent dose of cannabinoids per portion with a rapid time of onset. Indeed, the long time of onset of psychoactive effects and varied metabolic responses to these products result in a high risk of severe intoxication due to overconsumption. Sophisticated emulsion or hydrogel-based delivery systems are one potential tool to achieve this goal. To date, there is a lack of evidence linking specific classes of delivery systems with their pharmacokinetic profiles in humans. More research is needed to directly compare different classes of delivery systems for the gastrointestinal delivery of cannabinoids.

Pharmacokinetic and Safety Evaluation of Various Oral Doses of a Novel 1:20 THC:CBD Cannabis Herbal Extract in Dogs

Objective: To determine the pharmacokinetics (PK) and safety of various oral doses of a Cannabis herbal extract (CHE) containing a 1:20 ratio of Δ9-tetrahydrocannabinol (THC):cannabidiol (CBD) in 13 healthy Beagle-cross dogs.

Methods: Single-dose PK was assessed after oral administration of CHE at low, medium, or high doses [2, 5, or 10 mg CBD and 0.1, 0.25, or 0.5 mg THC per kg of body weight (bw), respectively; n = 6 per group]. Dogs were monitored for adverse events for up to 48 h post-dose. Evaluations of neurological signs, clinical laboratory abnormalities, and other adverse events were performed in two separate study phases: a multiple-dose phase with 12 dogs receiving five medium doses (5 mg CBD/kg bw) at 12 h intervals, and a single low-dose (2 mg CBD/kg bw), randomized, blinded, negative controlled study with 13 dogs.

Results: Cannabinoids CBD, THC, CBC, and metabolites 6-OH-CBD, 7-OH-CBD, 11-OH-THC, and THC-COOH were quantified in plasma. CBD and THC were rapidly absorbed (mean T_max of 1.9–2.3 h) and initially depleted rapidly (mean CBD T_1/2β of 2.3–2.6 h). A prolonged elimination phase (mean CBD T_1/2λ of 13.3–24.4 h) was observed. CBD and THC concentrations increased in a dose-dependent (non-linear) manner, with disproportionally greater cannabinoid exposure relative to the dose increase. Neurological signs (hyperesthesia or proprioceptive deficits) were noted in five of six dogs in the high-dose group, but only occasionally or rarely in the medium- and low-dose groups, respectively. Presence and severity of clinical signs correlated with plasma cannabinoid concentrations. Dogs appeared to develop a tolerance to cannabinoid effects after multiple CHE doses, with fewer neurological signs noted after the final (fifth) vs. first dose. No clinically meaningful changes in blood count or chemistry values occurred after multiple CHE doses.

Clinical Significance: Dogs tolerated the 1:20 THC:CBD formulation well at low and medium doses, but clinically meaningful neurological signs were observed at high doses. Because of non-proportional increases in plasma cannabinoid concentrations with increasing doses, as well as potential differences in CHE product composition and bioavailability, the possibility of adverse events and dose regimen consistency should be discussed with dog owners.