Comparative in vitro metabolism of the cannabinoids

Identification and Characterization of Cannabichromene's Major Metabolite Following Incubation with Human Liver Microsomes

Cannabichromene (CBC) is a minor cannabinoid within the array of over 120 cannabinoids identified in the Cannabis sativa plant. While CBC does not comprise a significant portion of whole plant material, it is available to the public in a purified and highly concentrated form. As minor cannabinoids become more popular due to their potential therapeutic properties, it becomes crucial to elucidate their metabolism in humans. Therefore, the goal of this was study to identify the major CBC phase I-oxidized metabolite generated in vitro following incubation with human liver microsomes. The novel metabolite structure was identified as 2'-hydroxycannabicitran using gas chromatography-mass spectrometry and nuclear magnetic resonance spectroscopy. Following the identification, in silico molecular modeling experiments were conducted and predicted 2'-hydroxycannabicitran to fit in the orthosteric site of both the CB1 and CB2 receptors. When tested in vitro utilizing a competitive binding assay, the metabolite did not show significant binding to either the CB1 or CB2 receptors. Further work necessitates the determination of potential activity of CBC and the here-identified phase I metabolite in other non-cannabinoid receptors.

Elucidating the Mechanism of Metabolism of Cannabichromene by Human Cytochrome P450s

Cannabichromene (CBC) is a nonpsychoactive phytocannabinoid well-known for its wide-ranging health advantages. However, there is limited knowledge regarding its human metabolism following CBC consumption. This research aimed to explore the metabolic pathways of CBC by various human liver cytochrome P450 (CYP) enzymes and support the outcomes using in vivo data from mice. The results unveiled two principal CBC metabolites generated by CYPs: 8'-hydroxy-CBC and 6',7'-epoxy-CBC, along with a minor quantity of 1″-hydroxy-CBC. Notably, among the examined CYPs, CYP2C9 demonstrated the highest efficiency in producing these metabolites. Moreover, through a molecular dynamics simulation spanning 1 μs, it was observed that CBC attains stability at the active site of CYP2J2 by forming hydrogen bonds with I487 and N379, facilitated by water molecules, which specifically promotes the hydroxy metabolite's formation. Additionally, the presence of cytochrome P450 reductase (CPR) amplified CBC's binding affinity to CYPs, particularly with CYP2C8 and CYP3A4. Furthermore, the metabolites derived from CBC reduced cytokine levels, such as IL6 and NO, by approximately 50% in microglia cells. This investigation offers valuable insights into the biotransformation of CBC, underscoring the physiological importance and the potential significance of these metabolites.

Δ9-tetrahydrocannabinol discrimination: Effects of route of administration in mice

Background

Route of administration is an important pharmacokinetic variable in development of translationally relevant preclinical models. Humans primarily administer cannabis through smoking, vaping, and edibles. In contrast, preclinical research has historically utilized injected Δ9-tetrahydrocannabinol (THC). The present study sought to examine how route of administration affected the potency and time course of THC's discriminative stimulus properties.

Methods

Adult female and male C57BL/6 mice were trained to discriminate intraperitoneal (i.p.) THC from vehicle in a drug discrimination procedure. After discrimination was acquired, a dose-effect curve was determined for i.p., oral (p.o.), subcutaneous (s.c.), and aerosolized THC. Subsequently, the time course of effects of each route of administration was determined.

Results

THC administered i.p., p.o., s.c., or via aerosolization fully substituted for i.p. THC. The potency of THC's psychoactive effects was similar for i.p., p.o., and s.c., except that THC was more potent when administered s.c. vs p.o. in females. All routes of administration had a similar potency in both sexes. The duration of THC's psychoactive effects was similar across i.p., s.c., and p.o. routes of administration, whereas aerosolized THC produced a faster onset and shorter duration of effects compared to the other routes.

Conclusion

THC administered via multiple routes of administration, including those commonly used in preclinical research (i.p. and s.c.) and more translationally relevant routes (aerosol and p.o.), produced THC-like discriminative stimulus effects in mice trained to discriminate i.p. THC. More precise predictions of THC's effects in humans may result from use of these translationally relevant routes of administration.

Evidence of 11-Hydroxy-hexahydrocannabinol and 11-Nor-9-carboxy-hexahydrocannabinol as Novel Human Metabolites of Δ9-Tetrahydrocannabinol

(-)-trans-Δ9-tetrahydrocannabinol (Δ9-THC) is the primary psychoactive compound in the Cannabis sativa plant. Δ9-THC undergoes extensive metabolism, with the main human phase I metabolites being 11-hydroxy-tetrahydrocannabinol (11-OH-THC) and 11-nor-9-carboxy-tetrahydrocannabinol (THC-COOH). Early animal studies have indicated that the 9-10 double bond may be reduced in vivo to yield 11-hydroxy-hexahydrocannabinol (11-OH-HHC) and 11-nor-9-carboxy-hexahydrocannabinol (HHC-COOH). These metabolites have not been confirmed in humans. In this study, we aimed to investigate whether this metabolic transformation occurs in humans. A range of cannabinoids and metabolites, including 11-OH-HHC and HHC-COOH, were measured in whole blood from 308 authentic forensic traffic cases, of which 222 were positive for Δ9-THC. HHC-COOH and 11-OH-HHC were detected in 84% and 15% of the Δ9-THC positive cases, respectively, and the estimated median concentration of HHC-COOH was 7%, relative to that of THC-COOH. To corroborate the in vivo findings, Δ9-THC and its metabolites 11-OH-THC and THC-COOH were incubated with pooled human liver microsomes. HHC-COOH was detected in both the Δ9-THC and 11-OH-THC incubations, while 11-OH-HHC was only detectable in the 11-OH-THC incubation. Hexahydrocannabinol was not detected in any of the incubations, indicating that it is 11-OH-THC or the corresponding aldehyde that undergoes double bond reduction with subsequent oxidation of the aliphatic alcohol to HHC-COOH. In summary, the presented data provide the first evidence of HHC-COOH and 11-OH-HHC being human phase I metabolites of Δ9-THC. These findings have implications for interpretation of analytical results from subjects exposed to Δ9-THC or HHC.

Hepatic biotransformation of non-psychotropic phytocannabinoids and activity screening on cytochromes P450 and UDP-glucuronosyltransferases

This study examined the biotransformation of phytocannabinoids in human hepatocytes. The susceptibility of the tested compounds to transformations in hepatocytes exhibited the following hierarchy: cannabinol (CBN) > cannabigerol (CBG) > cannabichromene (CBC) > cannabidiol (CBD). Biotransformation included hydroxylation, oxidation to a carboxylic acid, dehydrogenation, hydrogenation, dehydration, loss/shortening of alkyl, glucuronidation and sulfation. CBN was primarily metabolized by oxidation of a methyl to a carboxylic acid group, while CBD, CBG and CBC were preferentially metabolized by direct glucuronidation. The study also screened for the activity of recombinant human cytochromes P450 (CYPs) and UDP-glucuronosyltransferases (UGTs), which could catalyze the hydroxylation and glucuronidation of the tested compounds, respectively. We found that CBD was hydroxylated mainly by CYPs 2C8, 2C19, 2D6; CBN by 1A2, 2C9, 2C19 and 2D6; and CBG by 2B6, 2C9, 2C19 and 2D6. CBC exhibited higher susceptibility to CYP-mediated transformation than the other tested compounds, mainly with CYPs 1A2, 2B6, 2C8, 2C19, 2D6 and 3A4 being involved. Further, CBD was primarily glucuronidated by UGTs 1A3, 1A7, 1A8, 1A9 and 2B7; CBN by 1A7, 1A8, 1A9 and 2B7; CBG by 1A3, 1A7, 1A8, 1A9, 2B4, 2B7 and 2B17; and the glucuronidation of CBC was catalyzed by UGTs 1A1, 1A8, 1A9 and 2B7.

Identification of human hexahydrocannabinol metabolites in urine

Hexahydrocannabinol (HHC) is a cannabinoid that has been known since 1940 but has only recently found its way into recreational use as a psychoactive drug. HHC has been used as a legal alternative to tetrahydrocannabinol (THC) in many countries, but first countries already placed it under their narcotic substances law. Our aim was to evaluate a reliable analytical method for the proof of HHC consumption by LC-MS/MS and GC-MS. We identified the two epimers of HHC and metabolites after HHC consumption by two volunteers (inhalation by use of a vaporizer and oral intake). LC-HR-MS/MS, LC-MS/MS and GC-MS with literature data (EI-MS spectra of derivatives) and reference compounds - as far as commercially available - were used for metabolite identification. Phase-II-metabolites (glucuronides) of HHC and OH-HHC were found in urine samples with LC-HR-MS/MS and LC-MS/MS. The main metabolite was tentatively identified with GC-MS as 4'OH-HHC (stereochemistry on C9 and C4' unknown). Another major side-chain hydroxylated metabolite found by LC-MS/MS could not be unambiguously identified. Both epimers of 11-OH-HHC were found in considerable amounts in urine. (8R, 9R)-8-OH-HHC was identified as a minor metabolite with GC-MS and LC-MS/MS. While (9S)-HHC was found in urine after oral intake and inhalation of HHC, the more psychoactive epimer (9R)-HHC was only found in urine after inhalation. Several other minor metabolites were detected but not structurally identified. We found that after oral or inhalative consumption the urinary main metabolites of a diastereomeric mixture of HHC are different from the respective, major Δ9-THC metabolites (11-OH-Δ9-THC and 11-nor-9-carboxy-Δ9-THC). Although a sensitive LC-MS/MS and GC-SIM-MS method were set-up for the reference compounds (9R)-11-nor-9-carboxy-HHC and (9S)-11-nor-9-carboxy-HHC, these oxidation products were not detected in urine with these techniques. To further increase sensitivity, a GC-MS/MS method was developed, and the 11-nor-9-carboxy metabolites of HHC were confirmed to be present as minor metabolites.

Studies Pertaining to the Emerging Cannabinoid Hexahydrocannabinol (HHC)

We report studies pertaining to two isomeric hexahydrocannabinols (HHCs), (9R)-HHC and (9S)-HHC, which are derivatives of the psychoactive cannabinoids Δ9- and Δ8-THC. HHCs have been known since the 1940s, but have become increasingly available to the public in the United States and are typically sold as a mixture of isomers. We show that (9R)-HHC and (9S)-HHC can be prepared using hydrogen-atom transfer reduction, with (9R)-HHC being accessed as the major diastereomer. In addition, we report the results of cannabinoid receptor studies for (9R)-HHC and (9S)-HHC. The binding affinity and activity of isomer (9R)-HHC are similar to that of Δ9-THC, whereas (9S)-HHC binds strongly in cannabinoid receptor studies but displays diminished activity in functional assays. This is notable, as our examination of the certificates of analysis for >60 commercially available HHC products show wide variability in HHC isomer ratios (from 0.2:1 to 2.4:1 of (9R)-HHC to (9S)-HHC). These studies suggest the need for greater research and systematic testing of new cannabinoids. Such efforts would help inform cannabis-based policies, ensure the safety of cannabinoids, and potentially lead to the discovery of new medicines.

Review of the oral toxicity of cannabidiol (CBD)

Information in the published literature indicates that consumption of CBD can result in developmental and reproductive toxicity and hepatotoxicity outcomes in animal models. The trend of CBD-induced male reproductive toxicity has been observed in phylogenetically disparate organisms, from invertebrates to non-human primates. CBD has also been shown to inhibit various cytochrome P450 enzymes and certain efflux transporters, resulting in the potential for drug-drug interactions and cellular accumulation of xenobiotics that are normally transported out of the cell. The mechanisms of CBD-mediated toxicity are not fully understood, but they may involve disruption of critical metabolic pathways and liver enzyme functions, receptor-specific binding activity, disruption of testosterone steroidogenesis, inhibition of reuptake and degradation of endocannabinoids, and the triggering of oxidative stress. The toxicological profile of CBD raises safety concerns, especially for long term consumption by the general population.

Safety assessment and redox status in rats after chronic exposure to cannabidiol and cannabigerol

Cannabidiol (CBD) and cannabigerol (CBG) are the two main non-psychotropic phytocannabinoids with high application potential in drug development. Both substances are redox-active and are intensively investigated for their cytoprotective and antioxidant action in vitro. In this study, we focused on an in vivo safety evaluation and the effect of CBD and CBG on the redox status in rats in a 90-d experiment. The substances were administered orogastrically in a dose of 0.66 mg synthetic CBD or 0.66 mg/1.33 mg CBG/kg/day. CBD produced no changes in the red or white blood count or biochemical blood parameters in comparison to the control. No deviations in the morphology or histology of the gastrointestinal tract and liver were observed. After 90 d of CBD exposure, a significant improvement in redox status was found in the blood plasma and liver. The concentration of malondialdehyde and carbonylated proteins was reduced compared to the control. In contrast to CBD, total oxidative stress was significantly increased and this was accompanied by an elevated level of malondialdehyde and carbonylated proteins in CBG-treated animals. Hepatotoxic (regressive changes) manifestations, disruption in white cell count, and alterations in the ALT activity, level of creatinine and ionized calcium were also found in CBG-treated animals. Based on liquid chromatography-mass spectrometry analysis, CBD/CBG accumulated in rat tissues (in the liver, brain, muscle, heart, kidney and skin) at a low ng level per gram. Both CBD and CBG molecular structures include a resorcinol moiety. In CBG, there is an extra dimethyloctadienyl structural pattern, which is most likely responsible for the disruption to the redox status and hepatic environment. The results are valuable to further investigation of the effects of CBD on redox status and should contribute towards opening up critical discussion on the applicability of other non-psychotropic cannabinoids.

Vaporized Delta-9-tetrahydrocannabinol Inhalation in Female Sprague Dawley Rats: A Pharmacokinetic and Behavioral Assessment

BACKGROUND

Delta-9-tetrahydrocannabinol (THC) is the main psychoactive component of cannabis. Historically, rodent studies examining the effects of THC have used intraperitoneal injection as the route of administration, heavily focusing on male subjects. However, human cannabis use is often through inhalation rather than injection.

OBJECTIVE

We sought to characterize the pharmacokinetic and phenotypic profile of acutely inhaled THC in female rats, compared to intraperitoneal injection, to identify any differences in exposure of THC between routes of administration.

METHODS

Adult female rats were administered THC via inhalation or intraperitoneal injection. Serum samples from multiple time points were analyzed for THC and metabolites 11-hydroxy-delta-9-tetrahydrocannabinol and 11-nor-9-carboxy-delta-9-tetrahydrocannabinol using ultra-performance liquid chromatography-tandem mass spectrometry. Rats were similarly treated for locomotor activity analysis.

RESULTS

Rats treated with 2 mg/kg THC intraperitoneally reached a maximum serum THC concentration of 107.7 ± 21.9 ng/mL. Multiple THC inhalation doses were also examined (0.25 mL of 40 or 160 mg/mL THC), achieving maximum concentrations of 43.3 ± 7.2 and 71.6 ± 22.5 ng/mL THC in serum, respectively. Significantly reduced vertical locomotor activity was observed in the lower inhaled dose of THC and the intraperitoneal injected THC dose compared to vehicle treatment.

CONCLUSION

This study established a simple rodent model of inhaled THC, demonstrating the pharmacokinetic and locomotor profile of acute THC inhalation, compared to an i.p. injected THC dose in female subjects. These results will help support future inhalation THC rat research which is especially important when researching behavior and neurochemical effects of inhaled THC as a model of human cannabis use.

Pharmacological Aspects and Biological Effects of Cannabigerol and Its Synthetic Derivatives

Cannabigerol (CBG) is a cannabinoid from the plant Cannabis sativa that lacks psychotomimetic effects. Its precursor is the acidic form, cannabigerolic acid (CBGA), which is, in turn, a biosynthetic precursor of the compounds cannabidiol (CBD) and Δ9-tetrahydrocannabinol (THC). CBGA decarboxylation leads to the formation of neutral cannabinoid CBG, through a chemical reaction catalyzed by heat. On the basis of the growing interest in CBG and with the aim of highlighting scientific information on this phytocannabinoid, we focused the content of this article on its pharmacokinetic and pharmacodynamic characteristics and on its principal pharmacological effects. CBG is metabolized in the liver by the enzyme CYP2J2 to produce hydroxyl and di-oxygenated products. CBG is considered a partial agonist at the CB1 receptor (R) and CB2R, as well as a regulator of endocannabinoid signaling. Potential pharmacological targets for CBG include transient receptor potential (TRP) channels, cyclooxygenase (COX-1 and COX-2) enzymes, cannabinoid, 5-HT1A, and alpha-2 receptors. Pre-clinical findings show that CBG reduces intraocular pressure, possesses antioxidant, anti-inflammatory, and anti-tumoral activities, and has anti-anxiety, neuroprotective, dermatological, and appetite-stimulating effects. Several findings suggest that research on CBG deserves to be deepened, as it could be used, alone or in association, for novel therapeutic approaches for several disorders.

Metabolites of Cannabigerol Generated by Human Cytochrome P450s Are Bioactive

The phytocannabinoid cannabigerol (CBG) is the central biosynthetic precursor to many cannabinoids, including Δ⁹-tetrahydrocannabinol (THC) and cannabidiol (CBD). Though the use of CBG has recently witnessed a widespread surge because of its beneficial health effects and lack of psychoactivity, its metabolism by human cytochrome P450s is largely unknown. Herein, we describe comprehensive in vitro and in vivo cytochrome P450 (CYP)-mediated metabolic studies of CBG, ranging from liquid chromatography tandem mass spectrometry-based primary metabolic site determination, synthetic validation, and kinetic behavior using targeted mass spectrometry. These investigations revealed that cyclo-CBG, a recently isolated phytocannabinoid, is the major metabolite that is rapidly formed by selected human cytochrome P450s (CYP2J2, CYP3A4, CYP2D6, CYP2C8, and CYP2C9). Additionally, in vivo studies with mice administered with CBG supported these studies, where cyclo-CBG is the major metabolite as well. Spectroscopic binding studies along with docking and modeling of the CBG molecule near the heme in the active site of P450s confirmed these observations, pointing at the preferred site selectivity of CBG metabolism at the prenyl chain over other positions. Importantly, we found out that CBG and its oxidized CBG metabolites reduced inflammation in BV2 microglial cells stimulated with LPS. Overall, combining enzymological studies, mass spectrometry, and chemical synthesis, we showcase that CBG is rapidly metabolized by human P450s to form oxidized metabolites that are bioactive.

Pharmacokinetics of Cannabidiol in Sprague-Dawley Rats After Oral and Pulmonary Administration

Introduction: Cannabidiol (CBD) is primarily consumed through ingestion and inhalation. Little is known about how CBD pharmacokinetics differ between routes of administration, and duration of pulmonary exposure. Methods: Pharmacokinetics, brain distribution, and urinary elimination of CBD and its major metabolites (6-hydroxy-cannabidiol [6-OH-CBD], 7-hydroxy-cannabidiol [7-OH-CBD], 7-carboxy-cannabidiol [7-COOH-CBD], and CBD-glucuronide) were evaluated in adult Sprague-Dawley rats following a single oral CBD ingestion (10 mg/kg in medium chain triglyceride oil; 24 male animals), and 1 or 14 days of repeated inhalation (0.9-13.9 mg/kg in propylene glycol [41%/59% by weight]; 5 male and 5 female animals per dose). Blood and brain tissue were collected at a single time point from each animal. Collection times were staggered from 5 min to 24 h postoral gavage or first (blood only) and final inhalation. Urine was collected 24 h postoral gavage or final inhalation. Samples were analyzed through liquid chromatography-mass spectrometry (LC-MS/MS). Results: CBD was more rapidly absorbed following inhalation than ingestion (T_max=5 min and 2 h, respectively). Inhalation resulted in a dose-responsive increase in CBD C_max and AUC_last. CBD C_max was 24-fold higher following the highest pulmonary dose (13.9 mg/kg) versus an oral dose of comparable concentration (10 mg/kg). C_max and AUC_last (0-16 h) trended higher following repeated exposure. Elimination was notably faster with repeated CBD inhalation (t_1/2=5.3 and 2.4 h on days 1 and 14, respectively). While metabolites were detectable in plasma, AUC_last (0-2 h) was at least 10- (7-OH-CBD, 7-COOH-CBD) to 100- (6-OH-CBD) fold lower than the parent compound. Metabolite concentration trended higher following repeated inhalation (6.7 mg/kg CBD); AUC_last (0-16 h) was ∼1.8-, ∼1.4-, and ∼2.4-fold higher following 14 days of exposure for 6-OH-CBD, 7-OH-CBD, and 7-COOH-CBD, respectively. CBD was detectable in brain homogenate tissue 24-h after 14-day inhalation (>3.5 mg/kg deposited dose) or a single oral administration. CBD metabolites were only measurable in brain tissue following the highest inhaled dose (13.9 mg/kg CBD). CBD, but not metabolites, was detectable in urine for all dose groups following 2 weeks of CBD inhalation. Neither CBD nor metabolites were present in urine after oral administration. Conclusion: CBD pharmacokinetics differ across oral and pulmonary routes of administration and acute or repeated dosing.

Serum Cannabinoid 24 h and 1 Week Steady State Pharmacokinetic Assessment in Cats Using a CBD/CBDA Rich Hemp Paste

Hemp based cannabinoids have gained popularity in veterinary medicine due to the potential to treat pain, seizure disorders and dermatological maladies in dogs. Cat owners are also using hemp-based products for arthritis, anxiety and neoplastic disorders with no studies assessing hemp cannabinoids, namely cannabidiol efficacy, for such disorders. Initial twenty-four pharmacokinetic and chronic dosing serum concentration in cats are sparse. The aim of our study was to assess 8 cats physiological and 24 h and 1-week steady state pharmacokinetic response to a cannabidiol (CBD) and cannabidiolic acid (CBDA) rich hemp in a palatable oral paste. Using a standard dose of paste (6.4 mg/CBD + CBDA 5.3 mg/gram) across 8 cats weighing between 4.2 and 5.4 kg showed an average maximal concentration of CBD at 282.0 ± 149.4 ng/mL with a half-life of ~2.1 ± 1.1 h, and CBDA concentrations of 1,011.3 ± 495.4 ng/mL with a half-life of ~2.7 ± 1.4 h, showing superior absorption of CBDA. After twice daily dosing for 1 week the serum concentrations 6 h after a morning dosing showed that the acidic forms of the cannabinoids were approximately double the concentration of the non-acidic forms like CBD and Δ9- tetrahydrocannabinol (THC). The results of this study compared to two other recent studies suggest that the absorption in this specific paste product may be superior to oil bases used previously, and show that the acidic forms of cannabinoids appear to be absorbed better than the non-acidic forms. More importantly, physical and behavioral examinations every morning after dosing showed no adverse events related to neurological function or behavioral alterations. In addition, bloodwork after 1 week of treatment showed no clinically significant serum biochemical alterations as a reflection of hepatic and renal function all remaining within the reference ranges set by the diagnostic laboratory suggesting that short-term treatment was safe.

Prevalence of Cannabidiol, Δ9- and Δ8-Tetrahydrocannabinol and Metabolites in Workplace Drug Testing Urine Specimens

Given the recent popularity of cannabidiol (CBD) use and the emergence of Δ8-tetrahydrocannabinol (Δ8-THC), the prevalence and concentration of these and other cannabinoids was investigated in 2,000 regulated and 4,000 non-regulated specimens from workplace drug testing. All specimens were screened using LC-MS-MS for the presence of 7-hydroxy-CBD (7-OH-CBD) and ∆9-tetrahydrocannabinol-9-carboxylic acid (Δ9-THC-COOH), with a cutoff of 2 ng/mL. Specimens screening positive by LC-MS-MS were analyzed by immunoassay at 20, 50 and 100 ng/mL cutoffs, and by an LC-MS-MS confirmation method for 11 cannabinoids and metabolites with a 1 ng/mL cutoff. Using a 1 ng/mL cutoff, 98 (4.9%) regulated and 331 (8.3%) non-regulated specimens were positive for Δ9-THC-COOH. Of these, 64% had concentrations below 15 ng/mL. Similarly, 59 (3.0%) regulated and 162 (4.2%) non-regulated specimens were positive for 7-OH-CBD (n=210), CBD (n=120) and/or 7-carboxy-cannabidiol (CBD-COOH, n=120). The median concentrations of 7-OH-CBD, CBD and CBD-COOH in those 221 specimens were 6.3, 1.1 and 1.2 ng/mL, respectively. Δ8-Tetrahydrocannabinol-9-carboxylic acid (Δ8-THC-COOH) was identified in 76 (1.3%) specimens. Parent Δ8-THC is a minor cannabinoid in marijuana, which appears to account for the typically low Δ8-THC-COOH concentrations (median 3.4 ng/mL) in most positive specimens. However, elevated concentrations suggested use of Δ8-THC-containing products in some cases (range 1.0-415 ng/mL). Although 93% agreement was observed between confirmatory LC-MS-MS (15 ng/mL cutoff) and immunoassay (50 ng/mL cutoff), a false negative specimen (66 ng/mL Δ9-THC-COOH) was identified.

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.

Strain-, Sex-, and Time-Dependent Antidepressant-like Effects of Cannabidiol

Cannabidiol (CBD) is a non-intoxicating compound extracted from Cannabis sativa, showing antidepressant-like effects in different rodent models. However, inconsistent results have been described depending on the species and the strain used to assess depressive-like behavior. Moreover, only a few studies investigated the effect of CBD in female rodents. Therefore, we aimed to (i) investigate the effects of CBD in two different strains of mice (Swiss and C57BL/6) and a rat model of depression based on selective breeding (Flinders Sensitive and Resistant Lines, FSL and FRL) subjected to tests predictive of antidepressant-like effects and (ii) investigate the influence of sex in the effects of CBD in both mice and rats. CBD induced an antidepressant-like effect in male Swiss but not in female Swiss or C57BL/6 mice in the tail suspension test (TST). In male FSL rats, CBD produced an antidepressant-like effect 1 h post injection. However, in female FSL, CBD induced a bimodal effect, increasing the immobility time at 1 h and decreasing it at 2 h. In conclusion, strain, sex, and administration time affect CBD's behavioral response to rodents exposed to tests predictive of antidepressant effects.

Marijuana toxicosis in dogs in Melbourne, Australia, following suspected ingestion of human faeces: 15 cases (2011-2020)

This retrospective case series describes a novel and unexpected source for marijuana toxicosis in dogs; suspected ingestion of human faeces containing Δ⁹ -tetrahydrocannabinol (THC). Medical records from four, 24-h veterinary emergency hospitals in Melbourne, Australia, were reviewed and 15 dogs met the criteria for inclusion in this case series. Clinical signs of marijuana toxicosis included ataxia (n = 13), mydriasis (n = 6), hyperaesthesia (n = 5), urinary incontinence (n = 4) and stupor (n = 3). A urine drug screening test was performed for eight dogs and all were positive for THC. Confirmation of ingestion of human faeces was based on owner-witnessed ingestion (n = 7) or the presence of faecal material within vomit (n = 8). Sites of human faecal exposure were recorded to be a local park (n = 10), beach (n = 1), camp site (n = 1) and walking trail (n = 1). Time from exposure to development of clinical signs ranged between 3 and 6 h (n = 4). All dogs survived to discharge. Ingestion of human faeces containing THC may lead to marijuana toxicosis in dogs. Veterinary staff and owners should be attentive in regard to using appropriate hygiene measures when managing these dogs.

Emergence of the less common cannabinoid Δ8 -Tetrahydrocannabinol in a doping sample

Δ⁸ -Tetrahydrocannabinol (Δ⁸ -THC) as isomer of the well-known Δ⁹ -THC has a similar mode of action, and the potency was estimated to be two thirds compared with Δ⁹ -THC. Content of Δ⁸ -THC in plant material is low, but formulations containing Δ⁸ -THC in high concentrations are gaining popularity. Δ⁸ -THC is to be regarded as prohibited substance according to the Prohibited List of the World Anti-Doping Agency (WADA). Contradictory results between initial testing procedure and confirmatory quantitation for 11-Nor-9-carboxy-Δ⁹ -tetrahydrocannabinol (Δ⁹ -THC-COOH) of a doping control sample gave rise for follow-up testing procedures. After alkaline hydrolysis and liquid-liquid extraction, the sample was analyzed by high-performance liquid chromatography tandem mass spectrometry (HPLC-MS/MS) using isocratic elution instead of gradient elution, which is used for standard procedure. Isocratic elution resulted in two peaks instead of one using gradient elution. Both peaks showed same fragmentation. Using certified reference materials, one peak could be assigned to Δ⁹ -THC-COOH and the other one with higher intensity to the less common 11-Nor-9-carboxy-Δ⁸ -Tetrahydrocannabinol (Δ⁸ -THC-COOH) in a concentration of approximately 1200 ng/ml. As complementary method, gas chromatography tandem mass spectrometry (GC-MS/MS) can also be used for identification. Here Δ⁸ - and Δ⁹ -THC-COOH can be distinguished by chromatography and by fragmentation. Additional investigations of doping control samples containing Δ⁹ -THC-COOH revealed the simultaneous presence of Δ⁸ -THC-COOH in low concentrations (0.22-8.91 ng/ml) presumably due to plant origin. Percentage of Δ⁸ -THC-COOH varies from 0.05 to 2.83%. In vitro experiments using human liver microsomes showed that Δ⁸ -THC is metabolized in the same way as Δ⁹ -THC.

Sex, species and age: Effects of rodent demographics on the pharmacology of ∆9-tetrahydrocanabinol

Cannabis edibles are becoming more common in an increasingly diverse population of users, and the impact of first pass metabolism on cannabis's pharmacological profile across age and sex is not well understood. The present study examined the impact of age, sex and rodent species on the effects of intraperitoneal (i.p.) delta-9-tetrahydrocannabinol (THC) and its primary psychoactive metabolite, 11-OH-THC, in rodent models of psychoactivity and molecular assays of cannabinoid receptor type-1 (CB₁) pharmacology. Like oral THC, i.p. THC also undergoes first pass metabolism. In both species and sexes, 11-OH-THC exhibited marginally higher affinity (~1.5 fold) than THC and both served as partial agonists in [³⁵S]GTPγS binding with equivalent potency; 11-OH-THC exhibited slightly greater efficacy in rat brain tissue. In ICR mice, 11-OH-THC exhibited greater potency than THC in assays of catalepsy (7- to 15-fold) and hypothermia (7- to 31-fold). Further, 11-OH-THC was more potent in THC drug discrimination (7- to 9-fold) in C57Bl/6 J mice, with THC-like discriminative stimulus effects being CB₁-, but not CB₂-, mediated. THC's discriminative stimulus also was stable across age in mice, as its potency did not change over the course of the experiment (~17 months). While sex differences in THC's effects were not revealed in mice, THC was significantly more potent in females Sprague-Dawley rats than in males trained to discriminate THC from vehicle. This study demonstrates a cross-species in the psychoactive effects of i.p. THC across sex that may be related to differential metabolism of THC into its psychoactive metabolite 11-OH-THC, suggesting that species is a crucial design consideration in the preclinical study of phytocannabinoids.

Cannabinoidomics - An analytical approach to understand the effect of medical Cannabis treatment on the endocannabinoid metabolome

Increasing evidence for the therapeutic potential of Cannabis in numerous pathological and physiological conditions has led to a surge of studies investigating the active compounds in different chemovars and their mechanisms of action, as well as their efficacy and safety. The biological effects of Cannabis have been attributed to phytocannabinoid modulation of the endocannabinoid system. In-vitro and in-vivo studies have shown that pure phytocannabinoids can alter the levels of endocannabinoids and other cannabimimetic lipids. However, it is not yet understood whether whole Cannabis extracts exert variable effects on the endocannabinoid metabolome, and whether these effects vary between tissues. To address these challenges, we have developed and validated a novel analytical approach, termed "cannabinoidomics," for the simultaneous extraction and analysis of both endogenous and plant cannabinoids from different biological matrices. In the methodological development liquid chromatography high resolution tandem mass spectrometry (LC/HRMS/MS) was used to identify 57 phytocannabinoids, 15 major phytocannabinoid metabolites, and 78 endocannabinoids and cannabimimetic lipids in different biological matrices, most of which have no analytical standards. In the validation process, spiked cannabinoids were quantified with acceptable selectivity, repeatability, reproducibility, sensitivity, and accuracy. The power of this analytical method is demonstrated by analysis of serum and four different sections of mouse brains challenged with three different cannabidiol (CBD)-rich extracts. The results demonstrate that variations in the minor phytocannabinoid contents of the different extracts may lead to varied effects on endocannabinoid concentrations, and on the CBD metabolite profile in the peripheral and central systems. We also show that the Cannabis challenge significantly decreases the levels of several endocannabinoids in specific brain sections compared to the control group. This effect is extract-specific and suggests the importance of minor, other-than CBD, phytocannabinoid or non-phytocannabinoid compounds.

Cannabichromene

Cannabinochromene (CBC, 1a) is the archetypal member of a class of more than twenty isoprenylated 5-hydroxy-7-alkyl(aralky)benzo[2 H]pyranes first reported from Cannabis sativa L. but also occurring in unrelated plants ( Rhododendron species) as well as liverworts and fungi. The chemistry, synthesis, and bioactivity of CBC (1a) is reviewed, highlighting its underexploited pharmacological potential and rich chemistry.

A Systematic Review of the Complex Effects of Cannabinoids on Cerebral and Peripheral Circulation in Animal Models

While cannabis is perceived as a relatively safe drug by the public, accumulating clinical data suggest detrimental cardiovascular effects of cannabinoids. Cannabis has been legalized in several countries and jurisdictions recently. Experimental studies specifically targeting cannabinoids' effects on the cerebral vasculature are rare. There is evidence for transient vasoconstrictive effects of cannabinoids in the peripheral and cerebral vasculature in a complex interplay of vasodilation and vasoconstriction. Vasoreactivity to cannabinoids is dependent on the specific molecules, their metabolites and dose, baseline vascular tone, and vessel characteristics as well as experimental conditions and animal species. We systematically review the currently available literature of experimental results in in vivo and in vitro animal studies, examining cannabinoids' effects on circulation and reactive vasodilation or vasoconstriction, with a particular focus on the cerebral vascular bed.

Designing microorganisms for heterologous biosynthesis of cannabinoids

During the last decade, the use of medical Cannabis has expanded globally and legislation is getting more liberal in many countries, facilitating the research on cannabinoids. The unique interaction of cannabinoids with the human endocannabinoid system makes these compounds an interesting target to be studied as therapeutic agents for the treatment of several medical conditions. However, currently there are important limitations in the study, production and use of cannabinoids as pharmaceutical drugs. Besides the main constituent tetrahydrocannabinolic acid, the structurally related compound cannabidiol is of high interest as drug candidate. From the more than 100 known cannabinoids reported, most can only be extracted in very low amounts and their pharmacological profile has not been determined. Today, cannabinoids are isolated from the strictly regulated Cannabis plant, and the supply of compounds with sufficient quality is a major problem. Biotechnological production could be an attractive alternative mode of production. Herein, we explore the potential use of synthetic biology as an alternative strategy for synthesis of cannabinoids in heterologous hosts. We summarize the current knowledge surrounding cannabinoids biosynthesis and present a comprehensive description of the key steps of the genuine and artificial pathway, systems biotechnology needs and platform optimization.

In vitro metabolism and metabolic effects of ajulemic acid, a synthetic cannabinoid agonist

Ajulemic acid is a synthetic analog of Δ⁸-THC-11-oic acid, the terminal metabolite of Δ⁸-THC. Unlike Δ⁹-THC, the psychoactive principle of Cannabis, it shows potent anti-inflammatory action and has minimal CNS cannabimimetic activity. Its in vitro metabolism by hepatocytes from rats, dogs, cynomolgus monkeys and humans was studied and the results are reported here. Five metabolites, M1 to M5, were observed in human hepatocyte incubations. One metabolite, M5, a glucuronide, was observed in the chromatogram of canine hepatocyte incubations. In monkey hepatocyte incubations, M5 was observed in the chromatograms of both the 120 and 240 min samples, trace metabolite M1 (side-chain hydroxyl) was observed in the 120 min samples, and trace metabolite M4 (side-chain dehydrogenation) was observed in the 240 min samples. No metabolites were found in the rat hepatocyte incubations. Unchanged amounts of ajulemic acid detected after the 2-h incubation were 103%, 90%, 86%, and 83% for rat, dog, monkey, and human hepatocytes, respectively. Additional studies were done to ascertain if ajulemic acid can inhibit the activities of five principal human cytochrome P450 isozymes; CYP1A2, CYP2C9, CYP2C19, CYP2D6, and CYP3A4/5. In contrast to the phytocannabinoids Δ⁹-THC and CBD, no significant inhibition of cytochrome activity was observed. These data further support the conclusions reached in earlier reports on ajulemic acid's high margin of safety and suggest that it undergoes minimal metabolism and is not likely to interfere with the normal metabolism of drugs or endogenous substances.

Validation of Large White Pig as an animal model for the study of cannabinoids metabolism: application to the study of THC distribution in tissues

This study presents a new animal model, the Large White Pig, which was tested for studying cannabinoids metabolism. The first step has focused on determination of plasma kinetics after injection of Delta(9)-tetrahydrocannabinol (THC) at different dosages. Seven pigs received THC by intravenous injections (50, 100 or 200 microg/kg). Plasma samples were collected during 48 h. Determination of cannabinoids concentrations were performed by gas chromatography/mass spectrometry. Results showed that plasma kinetics were comparable to those reported in humans. Terminal half-life of elimination was 10.6 h and a volume of distribution of 32 l/kg was calculated. In a second step, this model was used to determine the kinetic profile of cannabinoids distribution in tissues. Eight Large White male pigs received an injection of THC (200 microg/kg). Two pigs were sacrificed 30 min after injection, two others after 2, 6 and 24 h. Different tissues were sampled: liver, kidney, heart, lung, spleen, muscle, fat, bile, blood, vitreous humor and several brain areas. The fastest THC elimination was noted in liver tissue, where it was completely eliminated in 6 h. THC concentrations decreased in brain tissue slower than in blood. The slowest THC elimination was observed for fat tissue, where the molecule was still present at significant concentrations 24 h later. After 30 min, THC concentration in different brain areas was highest in the cerebellum and lowest in the medulla oblongata. THC elimination kinetics noted in kidney, heart, spleen, muscle and lung were comparable with those observed in blood. 11-Hydroxy-THC was only found at high levels in liver. THC-COOH was less than 5 ng/g in most tissues, except in bile, where it increased for 24 h following THC injection. This study confirms, even after a unique administration, the prolonged retention of THC in brain and particularly in fat, which could be at the origin of different phenomena observed for heavy users such as prolonged detection of THC-COOH in urine or cannabis-related flashbacks. Moreover, these results support the interest for this animal model, which could be used in further studies of distribution of cannabinoids in tissues.

Stimulatory effects of testosterone and progesterone on the NADH- and NADPH-dependent oxidation of 7beta-hydroxy-delta8-tetrahydrocannabinol to 7-oxo-delta8-tetrahydrocannabinol in monkey liver microsomes

Microsomal alcohol oxygenase catalyzes the stereoselective oxidation of 7alpha- and 7beta-hydroxy-delta8-tetrahydrocannabinol (7alpha- and 7beta-hydroxy-delta8-THC) to 7-oxo-delta8-THC in monkey liver, and the activity for 7beta-hydroxy-delta8-THC is relatively higher than that for 7alpha-hydroxy-delta8-THC. We previously reported that purified P450JM-E, assumed to be CYP3A8, is a major enzyme responsible for the oxidation of 7-hydroxy-delta8-THC to 7-oxo-delta8-THC in monkey liver and is capable of catalyzing the oxidative reaction by NADH as well as NADPH. In the present study, we demonstrated that some steroids such as testosterone and progesterone stimulated both the NADH- and NADPH-dependent conversions of 7beta-hydroxy-delta8-THC to 7-oxo-delta8-THC in monkey liver microsomes. Kinetic analyses revealed that both the NADH- and NADPH-dependent 7-oxo-delta8-THC formation showed sigmoid kinetics. Testosterone caused a decrease in S50 and an increase in V(max) for the NADH-dependent activity, and resulted in a decrease in S50 without changing the V(max) for the NADPH-dependent activity. On the other hand, NADH-dependent testosterone 6beta-hydroxylation activity showed Michaelis-Menten kinetics and was also inhibited by 7beta-hydroxy-delta8-THC, resulting in a decrease in V(max) with no effect on the K(m). NADPH-dependent testosterone 6beta-hydrozylation activity was also inhibited by 7beta-hydroxy-delta8-THC, resulting in a decrease in both S50 and V(max). In order to explain the metabolic interaction between 7beta-hydroxy-delta8-THC and testosterone, we propose a kinetic model involving at least three binding sites, for the mechanism of activation by testosterone.

Pharmacokinetics and pharmacodynamics of cannabinoids

Delta(9)-Tetrahydrocannabinol (THC) is the main source of the pharmacological effects caused by the consumption of cannabis, both the marijuana-like action and the medicinal benefits of the plant. However, its acid metabolite THC-COOH, the non-psychotropic cannabidiol (CBD), several cannabinoid analogues and newly discovered modulators of the endogenous cannabinoid system are also promising candidates for clinical research and therapeutic uses. Cannabinoids exert many effects through activation of G-protein-coupled cannabinoid receptors in the brain and peripheral tissues. Additionally, there is evidence for non-receptor-dependent mechanisms. Natural cannabis products and single cannabinoids are usually inhaled or taken orally; the rectal route, sublingual administration, transdermal delivery, eye drops and aerosols have only been used in a few studies and are of little relevance in practice today. The pharmacokinetics of THC vary as a function of its route of administration. Pulmonary assimilation of inhaled THC causes a maximum plasma concentration within minutes, psychotropic effects start within seconds to a few minutes, reach a maximum after 15-30 minutes, and taper off within 2-3 hours. Following oral ingestion, psychotropic effects set in with a delay of 30-90 minutes, reach their maximum after 2-3 hours and last for about 4-12 hours, depending on dose and specific effect. At doses exceeding the psychotropic threshold, ingestion of cannabis usually causes enhanced well-being and relaxation with an intensification of ordinary sensory experiences. The most important acute adverse effects caused by overdosing are anxiety and panic attacks, and with regard to somatic effects increased heart rate and changes in blood pressure. Regular use of cannabis may lead to dependency and to a mild withdrawal syndrome. The existence and the intensity of possible long-term adverse effects on psyche and cognition, immune system, fertility and pregnancy remain controversial. They are reported to be low in humans and do not preclude legitimate therapeutic use of cannabis-based drugs. Properties of cannabis that might be of therapeutic use include analgesia, muscle relaxation, immunosuppression, sedation, improvement of mood, stimulation of appetite, antiemesis, lowering of intraocular pressure, bronchodilation, neuroprotection and induction of apoptosis in cancer cells.

Monkey hepatic microsomal alcohol oxygenase: purification and characterization of a cytochrome P450 enzyme catalyzing the stereoselective oxidation of 7alpha- and 7beta-hydroxy-delta8-tetrahydrocannabinol to 7-oxo-delta8-tetrahydrocannabinol

The formation of 7-oxo-delta8-tetrahydrocannabinol (7-Oxo-delta8-THC) from 7alpha- or 7beta-hydroxy-delta8-THC (7alpha- or 7beta-OH-delta8-THC) was found in hepatic microsomes of monkeys. The activity in 7beta-OH-delta8-THC was stereoselectively 2.5- to 4.6-fold higher than that from 7alpha-OH-delta8-THC. The oxidative activities of 7alpha- and 7beta-OH-delta8-THC to 7-Oxo-delta8-THC were inhibited to 35% and 10%, respectively, of the control value by the antibody against P450GPF-B (CYP3A), a major enzyme responsible for the formation of 7-Oxo-delta8-THC in guinea pigs. In the Lineweaver-Burk double-reciprocal plot analysis, testosterone 6beta-hydroxylase activity was competitively inhibited by 7beta-OH-delta8-THC. Two cytochrome P450 enzymes, called P450JM-D and P450JM-E, were purified from hepatic microsomes of Japanese monkeys. P450JM-E, assumed to be CYP3A8, immunologically reacted with the antibody against P450GPF-B and showed high forming activity of 7-Oxo-delta8-THC from 7-OH-delta8-THC. On the other hand, 7-Oxo-delta8-THC forming activity of P450JM-D, assumed to be CYP2C, was less than 10% of that of P450JM-E (CYP3A8). Oxygen-18 (18O) derived from atmospheric oxygen was incorporated into about 40% of the corresponding ketone formed from 7alpha-OH-delta8-THC or 8beta-OH-delta9-THC by P450JM-E (CYP3A8), although the incorporation of the stable isotope into the oxidized metabolite from 7beta-OH-delta8-THC or 8alpha-OH-delta9-THC was negligible. These results indicate that P450JM-E (CYP3A8) is a major enzyme of the oxidation of 7-OH-delta8-THC in monkey hepatic microsomes. The oxidation mechanism may proceed as follows: the alpha- and beta-epimers of 7-OH-delta8-THC or 8-OH-delta9-THC may be converted to ketone through dehydration of an enzyme-bound gem-diol by P450JM-E (CYP3A8), although this stereoselective dehydration differentiates between two epimers.

Recent advances in the metabolism of cannabinoids

This review describes recent advances in the metabolism of cannabinoids. Cannabidiol was metabolized to cannabielsoin, 6 beta-hydroxymethyl-delta 9-tetrahydrocannabinol and an oxepine derivative through epoxide intermediates by hepatic microsomal enzymes containing cytochrome P450 of animals. Cannabidiol inactivated cytochrome P450 UT-2 (CYP2C11) not equal to in male rats and a member of 3A subfamily in mouse liver. These inactivations may be very important because serious drug-drug interactions will occur in the case that cannabidiol is co-administered with drugs which are metabolized mainly by the enzyme system containing these P450 isozymes. A member of cytochrome P450 belonging to 2C subfamily was the major isozymes responsible for the cannabinoid metabolism in many experimental animals and that of 3A subfamily made some contribution to the metabolism of cannabinoids by human hepatic microsomes. Microsomal aldehyde oxygenase, a particular isozyme of cytochrome P450 catalyzing the oxidation of 11-oxo-tetrahydrocannabinol to tetrahydrocannabinol-11-oic acid, was found for the first time by the authors. Cytochrome P450 MUT-2 (CYP2C29) is the major isozyme responsible for the microsomal aldehyde oxygenase activity in mouse hepatic microsomes.

Mammary excretion of cannabidiol in rabbits after intravenous administration

The present study examined the distribution of cannabidiol into milk after an intravenous bolus injection (3 mg kg-1) to lactating rabbits. Drug concentrations in milk and serum were measured by HPLC. Cannabidiol was excreted into milk rapidly and the drug levels in milk increased over a 4-24-h period following the maternal injection. The mean milk to serum concentration ratio was 25.9, indicating a significant accumulation of the drug in milk.

A cytochrome P450 isozyme having aldehyde oxygenase activity plays a major role in metabolizing cannabinoids by mouse hepatic microsomes

A cytochrome P450 (designated P450 MUT-2) which catalyses the oxidation of 11-oxo-delta 8-tetrahydrocannabinol (11-oxo-delta 8-THC) to delta 8-THC-11-oic acid has been purified from hepatic microsomes of untreated male mice. Analysis of NH2-terminal sequence suggests that the isozyme is a member of the P450 2C gene subfamily. P450 MUT-2 exhibited aldehyde oxygenase activity for 11-oxo-delta 8-TH, 11-oxo-delta 9-THC, 11-oxo-cannabinol (11-oxo-CBN) and 9-anthraldehyde together with high activity for the hydroxylation of cannabinoids at the 11-position. Antibody against P450 MUT-2 significantly inhibited the microsomal formation of delta 8-THC-11-oic acid from 11-oxo-delta 8-THC, but not that of 9-anthracene carboxylic acid from 9-anthraldehyde. Major metabolic reactions of delta 8-THC, delta 9-THC and CBN with mouse hepatic microsomes were the 11-hydroxylation (all cannabinoids), 7 alpha-(delta 8-THC) or 8 alpha-hydroxylation (delta 9-THC) and epoxide formation (delta 8- and delta 9-THC). All these reactions except for 7 alpha-hydroxylation of delta 8-THC and alpha-epoxide formation from delta 9-THC were also markedly inhibited by the antibody. These results indicate that P450 MUT-2 is a major enzyme for metabolizing cannabinoids by mouse hepatic microsomes.