Influence of chronic oral intake of cannabis extract on oxidative and hydrolytic metabolism of xenobiotics in rat

Efficacy and safety of cannabidiol for the treatment of canine osteoarthritis: a systematic review and meta-analysis of animal intervention studies

Introduction

Canine osteoarthritis (OA) is a degenerative disease with chronic inflammation of internal and external joint structures in dogs. Cannabis spp. contains cannabidiol (CBD), a substance known for various potential indications, such as pain relief and anti-inflammatory in various types of animals, including dogs with OA. As CBD is increasingly in the spotlight for medical use, we aimed to perform a systematic review and meta-analysis to evaluate the efficacy and safety of CBD in treating canine OA.

Methods

We searched PubMed, Embase, Scopus, and CAB Direct for animal intervention studies investigating the effects of CBD for canine OA from database inception until February 28, 2023. Study characteristics and findings were summarized. A risk of bias in the included studies was assessed. Meta-analyses were performed using a random-effects model to estimate the effects of CBD on pain scores (0-10), expressed as mean difference (MD) and 95% confidence interval (95% CI). Certainty of evidence was assessed using GRADE.

Results

Five articles were included, which investigated the effects of CBD in 117 dogs with OA. All studies were rated as having a high risk of bias. CBD products varied substantially, i.e., oral full-spectrum CBD oil in four studies, and isolated CBD oil and liposomal CBD oil in another study. Treatment duration varied from 4-12 weeks. Meta-analyses of three studies found that, in dogs with OA, treatment with oral full-spectrum CBD oil may reduce pain severity scores (MD; -0.60, 95% CI; -1.51 to 0.31, I2 = 45.64%, p = 0.19) and pain interference scores (MD; -1.52, 95% CI; -3.84 to 0.80, I2 = 89.59%, p = 0.20) but the certainty of evidence was very low. CBD is generally considered safe and well-tolerated in the short-run, with few mild adverse events observed, such as vomiting and asymptomatic increase in alkaline phosphatase level.

Conclusion

CBD is considered safe for treating canine OA. CBD may reduce pain scores, but the evidence is very uncertain to conclude its clinical efficacy. High-quality clinical trials are needed to further evaluate the roles of CBD in canine OA.

Randomized blinded controlled clinical trial to assess the effect of oral cannabidiol administration in addition to conventional antiepileptic treatment on seizure frequency in dogs with intractable idiopathic epilepsy

OBJECTIVE

To assess the effect of oral cannabidiol (CBD) administration in addition to conventional antiepileptic treatment on seizure frequency in dogs with idiopathic epilepsy.

DESIGN

Randomized blinded controlled clinical trial.

ANIMALS

26 client-owned dogs with intractable idiopathic epilepsy.

PROCEDURES

Dogs were randomly assigned to a CBD (n = 12) or placebo (14) group. The CBD group received CBD-infused oil (2.5 mg/kg [1.1 mg/lb], PO) twice daily for 12 weeks in addition to existing antiepileptic treatments, and the placebo group received noninfused oil under the same conditions. Seizure activity, adverse effects, and plasma CBD concentrations were compared between groups.

RESULTS

2 dogs in the CBD group developed ataxia and were withdrawn from the study. After other exclusions, 9 dogs in the CBD group and 7 in the placebo group were included in the analysis. Dogs in the CBD group had a significant (median change, 33%) reduction in seizure frequency, compared with the placebo group. However, the proportion of dogs considered responders to treatment (≥ 50% decrease in seizure activity) was similar between groups. Plasma CBD concentrations were correlated with reduction in seizure frequency. Dogs in the CBD group had a significant increase in serum alkaline phosphatase activity. No adverse behavioral effects were reported by owners.

CONCLUSIONS AND CLINICAL RELEVANCE

Although a significant reduction in seizure frequency was achieved for dogs in the CBD group, the proportion of responders was similar between groups. Given the correlation between plasma CBD concentration and seizure frequency, additional research is warranted to determine whether a higher dosage of CBD would be effective in reducing seizure activity by ≥ 50%.

Pharmacokinetics, Safety, and Clinical Efficacy of Cannabidiol Treatment in Osteoarthritic Dogs

Objectives: The objectives of this study were to determine basic oral pharmacokinetics, and assess safety and analgesic efficacy of a cannabidiol (CBD) based oil in dogs with osteoarthritis (OA).

Methods: Single-dose pharmacokinetics was performed using two different doses of CBD enriched (2 and 8 mg/kg) oil. Thereafter, a randomized placebo-controlled, veterinarian, and owner blinded, cross-over study was conducted. Dogs received each of two treatments: CBD oil (2 mg/kg) or placebo oil every 12 h. Each treatment lasted for 4 weeks with a 2-week washout period. Baseline veterinary assessment and owner questionnaires were completed before initiating each treatment and at weeks 2 and 4. Hematology, serum chemistry and physical examinations were performed at each visit. A mixed model analysis, analyzing the change from enrollment baseline for all other time points was utilized for all variables of interest, with a p ≤ 0.05 defined as significant.

Results: Pharmacokinetics revealed an elimination half-life of 4.2 h at both doses and no observable side effects. Clinically, canine brief pain inventory and Hudson activity scores showed a significant decrease in pain and increase in activity (p < 0.01) with CBD oil. Veterinary assessment showed decreased pain during CBD treatment (p < 0.02). No side effects were reported by owners, however, serum chemistry showed an increase in alkaline phosphatase during CBD treatment (p < 0.01).

Clinical significance: This pharmacokinetic and clinical study suggests that 2 mg/kg of CBD twice daily can help increase comfort and activity in dogs with OA.

Disposition of the Emerging Brominated Flame Retardant, 2-Ethylhexyl 2,3,4,5-Tetrabromobenzoate, in Female SD Rats and Male B6C3F1 Mice: Effects of Dose, Route, and Repeated Administration

2-Ethylhexyl-2,3,4,5-tetrabromobenzoate (EH-TBB; MW 549.92 g/mol; CAS 183658-27-7) is a brominated component of flame retardant mixtures used as substitutes for some PBDEs. EH-TBB is added to various consumer products, including polyurethane foams, and has been detected in humans. The present study characterized the fate of EH-TBB in rodents. [¹⁴C]-labeled EH-TBB was absorbed, metabolized, and eliminated via the urine and feces following single administrations of 0.1-100 µmol/kg (∼0.05-55 mg/kg) or repeated administration (0.1 µmol/kg/day × 5-10 days) by gavage to female Hsd:Sprague DawleySD (SD) rats. Cumulative excretion via feces increased (39-60%) with dose (0.1-10 µmol/kg) with corresponding decreases in urinary excretion (54 to 37%) after 72 h. Delayed excretion of [¹⁴C]-radioactivity in urine and feces of a 100 µmol/kg oral dose was noted. Recovery was complete for all doses by 72 h. IV-injected rats excreted more of the 0.1 µmol/kg dose in urine and less in feces than did gavaged rats, indicating partial biliary elimination of systemically available compound. No tissue bioaccumulation was found for rats given 5 oral daily doses of EH-TBB. Parent molecule was not detected in urine whereas 2 metabolites, tetrabromobenzoic acid (TBBA), a TBBA-sulfate conjugate, and a TBBA-glycine conjugate were identified. EH-TBB and TBBA were identified in extracts from feces. Data from gavaged male B6C3F1/Tac mice indicated minimal sex- or species differences are likely for the disposition of EH-TBB. Approximately 85% of a 0.1 µmol/kg dose was absorbed from the gut. Overall absorption of EH-TBB is expected to be even greater at lower levels.

Harm reduction--the cannabis paradox

This article examines harm reduction from a novel perspective. Its central thesis is that harm reduction is not only a social concept, but also a biological one. More specifically, evolution does not make moral distinctions in the selection process, but utilizes a cannabis-based approach to harm reduction in order to promote survival of the fittest. Evidence will be provided from peer-reviewed scientific literature that supports the hypothesis that humans, and all animals, make and use internally produced cannabis-like products (endocannabinoids) as part of the evolutionary harm reduction program. More specifically, endocannabinoids homeostatically regulate all body systems (cardiovascular, digestive, endocrine, excretory, immune, nervous, musculo-skeletal, reproductive). Therefore, the health of each individual is dependant on this system working appropriately.

Pharmacokinetics and metabolism of 14C-levetiracetam, a new antiepileptic agent, in healthy volunteers

The absorption, disposition and metabolism of levetiracetam, a new antiepileptic drug, have been investigated after a single oral dose of the (14)C-labelled molecule administered to male healthy volunteers. As chiral inversion can occur during drug metabolism, the chiral inversion of levetiracetam and/or of its major metabolite produced by hydrolysis (the corresponding acid) was also investigated. Finally, the in vitro hydrolysis of levetiracetam to its major metabolite and the inhibition of this reaction in human blood have been studied. Levetiracetam was very rapidly absorbed in man, with the peak plasma concentration of the unchanged drug occurring at 0.25-0.50 h. The unchanged drug accounted for a very high percentage of plasma radioactivity (97-82%) at all the times measured, i.e. until 48 h after administration. The apparent volume of distribution of the compound was close (0.55-0.62 l/kg) to the volume of total body water. Total body clearance (0.80-0.97 ml/min/kg) was much lower than the nominal hepatic blood flow. The plasma elimination half-life of the unchanged drug varied between 7.4 h and 7.9 h. Plasma to blood ratio of total radioactivity concentrations was 1.1-1.3, showing that radioactivity concentrations were similar in blood cells and plasma. The balance of excretion was very high in all four volunteers. The predominant route of excretion was via urine, accounting for a mean of 95% of the administered dose after 4 days. Two major radioactive components were present in urine, the unchanged drug and the acid obtained by hydrolysis, accounting for 66% and 24% of the dose after 48 h, respectively. Hydrolysis of levetiracetam in human blood followed Michaelis-Menten kinetics with Km and V(max) values of 435 microM and 129 pmol/min/ml blood, respectively. Among the inhibitory agents investigated in this study, only paraoxon inhibited levetiracetam hydrolysis (92% inhibition at 100 microM). Oxidative metabolism occurred in man, although it accounted for no more than 2.5% of the dose. There was no evidence of chiral inversion.

Narcotic drugs change the expression of cytochrome P450 2E1 and 2C6 and other activities of carcinogen-metabolizing enzymes in the liver of male mice

Drug-metabolizing enzymes play a great role in the bioactivation and also detoxification of zenobiotics and carcinogens such as N-nitrosamines and polycyclic aromatic hydrocarbons (PAHs). Therefore, the present study was undertaken to investigate the effect of narcotic drugs such as cannabis (hashish) and diacetylmorphine (heroin) on the activity of N-nitrosodimethylamine N-demethylase I [NDMA-dI], arylhydrocarbon [benzo(a)pyerne] hydroxylase [AHH], cytochrome P450 (CYP), cytochrome b(5), NADPH-cytochrome c reductase, glutathione-S-transferase, and levels of glutathione and thiobarbituric acid-reactive substances (TBARS). In addition, the present study showed the influence of hashish and heroin after single (24 h) and repeated-dose treatments (4 consecutive days) on the expression of cytochrome P450 2E1 (CYP 2E1) and cytochrome P450 2C6 (CYP 2C6). The expression of CYP 2E1 was slightly induced after single-dose and markedly induced after repeated dose-treatments of mice with hashish (10 mg kg(-1) body weight). Contrarily, heroin markedly induced the expression of CYP 2C6 after single-dose and potentially reduced this expression after repeated-dose treatments. It is believed that N-nitrosamines are activated principally by CYP 2E1 and in support of this, the activity of NDMA-dI was found to be increased after single- and repeated-dose treatments of mice with hashish by 23 and 41%, respectively. In addition, single- and repeated-dose treatments of mice with hashish increased: (1) the total hepatic content of CYP by 112 and 206%, respectively; (2) AHH activity by 110 and 165%, respectively; (3) NADPH-cytochrome c reductase activity by 21 and 98%, respectively; (4) and glutathione level by 81 and 173%, respectively. Also, single-dose treatments of mice with heroin increased the total hepatic content of CYP, AHH, NADPH-cytochrome c reductase, and glutathione level by 126, 72, 39, 205%, respectively. However, repeated dose-treatments of mice with heroin did not change such activities except cytochrome c reductase activity increased by 20%. Interestingly, the level of free radicals, TBARS, was potentially decreased after single or repeated-dose treatments with either hashish or heroin. It is clear from this study that the effects of hashish are different from those of heroin on the above mentioned enzymes particularly after repeated dose treatments. It is concluded that hashish induced the expression of CYP 2E1 and other carcinogen-metabolizing enzymes activities, and this induction could potentiate the deleterious effects of N-nitrosamines and aromatic hydrocarbons, e.g. benzo(a)pyrene, upon the liver and probably other organs. Such alterations may also change the therapeutic actions of other drugs, which are primarily metabolized by the P450 system, when administered to peoples using hashish or heroin.

Liver disease due to illicit substance use

While the adverse neurological, cardiovascular, renal, haematologic and musculoskeletal consequences of the use of various illicit substances are widely appreciated, less attention has been directed to possible hepatotoxic effects. This is an important issue in view of increasing evidence in both experimental animals and humans that the use of some illicit substances may be associated with substantial liver damage, leading on occasion to acute liver failure. This manuscript reviews the effects on the liver of some of the most commonly used illicit substances, including ecstasy (3,4-methylenedioxymethamphetamine), other amphetamines, cocaine, heroin, angel dust (phencyclidine), lysergic acid diethylamide and marijuana. Additional causes of liver damage in those using illicit substances are discussed.

Chronic cannabinoid, CP-55,940, administration alters biotransformation in the rat

The objective of this study was to investigate the effects of single and repeated administration of CP-55,940 [(-)-cis-3-[2-hydroxy-4-(1, 1-dimethylheptyl)-phenyl]-trans-4-(3-hydroxypropyl)cyclohexanol)] on behaviour, energy metabolism and biotransformation. Single intraperitoneal administration to male Sprague-Dawley rats of CP-55,940 (0.4 mg/kg), induced a behavioural response characterized by 'splayed hind limbs', antinociception, hypothermia and a decrease in locomotor activity. Brain and liver mitochondria of the CP-55,940-treated rats exhibited an increase in respiration and no changes in ADP/O and citrate synthase specific activity. Repeated intraperitoneal administration of CP-55,940 (0.4 mg/kg, 11 days) induced behavioural tolerance, disappearance of the increase in the mitochondrial oxygen consumption as well as an increase in the monooxygenase activities and the content of liver microsomal cytochrome P450. Some hepatic metabolizing enzymes of the cytosolic glutathione-centre system were also affected. Previous studies had indicated that the tolerance after chronic administration of CP-55,940 could be due to down-regulation of brain cannabinoid receptors. The present findings demonstrate that the behavioural tolerance occurs together with modified biotransformation activities.

Thiacetazone--avoid like poison or use with care?

Recent 5 reports of severe cutaneous hypersensitivity reactions in patients infected with human immunodeficiency virus (HIV) and with tuberculosis treated with thiacetazone have prompted the World Health Organization to advise against the use of thiacetazone in patients known, or suspected, to be infected with HIV. Because the poorest countries will have great difficulty in replacing thiacetazone, the history, metabolism and possible mechanisms underlying the toxicity of this inexpensive, but problematic, drug are reviewed. Guidelines for National Tuberculosis Control Programme policies in response to thiacetazone toxicity are discussed, taking into account the differing levels of resources available to developing countries.

Selective stimulation of carboxylesterases metabolizing charged steroid esters by hydrocortisone

We observed a remarkable augmentation in the rate of hydrolytic breakdown of HCHS following exposure to corticosteroid therapy. This underscores the need for a careful reappraisal of its dosage in long term therapy. In such an event the uncharged ester may be the preferred drug of choice.