Oral and intravenous toxicity of delta9-tetrahydrocannabinol in rhesus monkeys

The Development of Cannabinoids as Therapeutic Agents in the United States

Cannabis is one of the oldest and widely used substances in the world. Cannabinoids within the cannabis plant, known as phytocannabinoids, mediate cannabis' effects through interactions with the body's endogenous cannabinoid system. This endogenous system, the endocannabinoid system, has important roles in physical and mental health. These roles point to the potential to develop cannabinoids as therapeutic agents while underscoring the risks related to interfering with the endogenous system during nonmedical use. This scoping narrative review synthesizes the current evidence for both the therapeutic and adverse effects of the major (i.e., Δ9-tetrahydrocannabinol and cannabidiol) and lesser studied minor phytocannabinoids, from nonclinical to clinical research. We pay particular attention to the areas where evidence is well established, including analgesic effects after acute exposures and neurocognitive risks after acute and chronic use. In addition, drug development considerations for cannabinoids as therapeutic agents within the United States are reviewed. The proposed clinical study design considerations encourage methodological standards for greater scientific rigor and reproducibility to ultimately extend our knowledge of the risks and benefits of cannabinoids for patients and providers. SIGNIFICANCE STATEMENT: This work provides a review of prior research related to phytocannabinoids, including therapeutic potential and known risks in the context of drug development within the United States. We also provide study design considerations for future cannabinoid drug development.

Effects of Δ9-Tetrahydrocannabinol and the Aminoalkylindole K2/Spice Constituent JWH-073 on Cardiac Tissue and Mesenteric Vascular Reactivity

Background: Although use of Cannabis sativa is not associated with serious adverse effects, recreational use of aminoalkylindole (AAI) cannabinoid receptor agonists found in K2/Spice herbal blends has been reported to cause adverse cardiovascular events, including angina, arrhythmia, changes in blood pressure, ischemic stroke, and myocardial infarction. Δ9-Tetrahydrocannabinol (Δ9-THC) is the primary CB1 agonist found in cannabis and JWH-073 is one of the AAI CB1 agonists found in K2/Spice brands sold to the public. Methods: This study used in vitro, in vivo, and ex vivo approaches to investigate potential differences on cardiac tissue and vascular effects betweenJWH-073 and Δ9-THC. Male C57BL/6 mice were treated with JWH-073 or Δ9-THC and cardiac injury was assessed by histology. Effects of JWH-073 and Δ9-THC on H9C2 cell viability and ex vivo mesenteric vascular reactivity were also determined. Results: JWH-073 or Δ9-THC induced typical cannabinoid effects of antinociception and hypothermia but did not promote death of cardiac myocytes. No differences in cell viability were observed in cultured H9C2 cardiac myocytes after 24 h of treatment. In isolated mesenteric arteries from drug-naive animals, JWH-073 produced significantly greater maximal relaxation (96%±2% vs. 73%±5%, p<0.05) and significantly greater inhibition of phenylephrine-mediated maximal contraction (Control 174%±11%KMAX) compared with Δ9-THC (50%±17% vs. 119%±16%KMAX, p<0.05). Discussion: These findings suggest that neither cannabinoid at the concentrations/dose studied caused cardiac cell death, but JWH-073 has the potential for greater vascular adverse events than Δ9-THC through an increased vasodilatory effect.

Comparison of the Neurotoxic and Seizure-Inducing Effects of Synthetic and Endogenous Cannabinoids with Δ9-Tetrahydrocannabinol

Introduction: Synthetic cannabinoids (SCs) are commonly found in preparations used as recreational drugs. Although severe adverse health effects are not generally associated with cannabis use, a rising number of studies document seizures and even death after SC use. In this study, a mouse model is used to investigate the hypothesis that SCs are more toxic than Δ⁹-tetrahydrocannabinol (THC), the principal psychoactive constituent of cannabis.

Materials and Methods: Beginning with the SCs, JWH-073 and AM-2201, dose–response curves were generated to find the dose of each drug that was similarly efficacious to 50 mg/kg THC. Mice were given daily intraperitoneal (IP) injections of vehicle, 50 mg/kg THC, 30 mg/kg JWH-073, or 1 mg/kg AM-2201 until tolerance to the antinociceptive and hypothermic effects was complete, and then were assessed for spontaneous and antagonist-precipitated withdrawal and potential organ damage. No differences in tolerance were noted, but AM-2201 showed more rearing in the spontaneous and antagonist-precipitated withdrawal phases than either vehicle or the other two drug treatments. Histopathological examination of these mice revealed no drug-induced lesions. In a subsequent set of experiments, various doses of THC, methanandamide (mAEA), and of a variety of SCs (HU-210, CP55940, JWH-073, AM-2201, and PB-22) were given IP, and convulsions and change in body temperature were quantified.

Discussion: The treatments yielded varying numbers of convulsions and a range of changes in body temperature. JWH-073 and AM-2201 produced significantly more convulsions than THC, HU-210, mAEA, or cannabidiol (CBD) (the latter two producing none). HU-210, CP55940, JWH-073, and mAEA produced greater hypothermia than THC or CBD. Convulsions and hypothermia induced by several agonists were prevented by pretreatment with a CB₁ antagonist, but not a CB₂ antagonist.

Conclusions: In agreement with human studies and case reports, this study found that SCs generally produced more seizures than THC. Of particular significance was the finding that mAEA produced far greater hypothermia than THC (similar to most SCs), but unlike the SCs and THC, produced no seizures.

Alcohol, drugs, caffeine, tobacco, and environmental contaminant exposure: reproductive health consequences and clinical implications

Reproductive function and fertility are thought to be compromised by behaviors such as cigarette smoking, substance abuse, and alcohol consumption; however, the strength of these associations are uncertain. Furthermore, the reproductive system is thought to be under attack from exposure to environmental contaminants, particularly those chemicals shown to affect endocrine homeostasis. The relationship between exposure to environmental contaminants and adverse effects on human reproductive health are frequently debated in the scientific literature and these controversies have spread into the lay press drawing increased public and regulatory attention. Therefore, the objective of the present review was to critically evaluate the literature concerning the relationship between lifestyle exposures and adverse effects on fertility as well as examining the evidence for a role of environmental contaminants in the purported decline of semen quality and the pathophysiology of subfertility, polycystic ovarian syndrome, and endometriosis. The authors conclude that whereas cigarette smoking is strongly associated with adverse reproductive outcomes, high-level exposures to other lifestyle factors are only weakly linked with negative fertility impacts. Finally, there is no compelling evidence that environmental contaminants, at concentrations representative of the levels measured in contemporary biomonitoring studies, have any effect, positive or negative, on reproductive health in the general population. Further research using prospective study designs with robust sample sizes are needed to evaluate testable hypotheses that address the relationship between exposure and adverse reproductive health effects.

Jekyll and hyde: two faces of cannabinoid signaling in male and female fertility

Mammalian reproduction is a complicated process designed to diversify and strengthen the genetic complement of the offspring and to safeguard regulatory systems at various steps for propagating procreation. An emerging concept in mammalian reproduction is the role of endocannabinoids, a group of endogenously produced lipid mediators, that bind to and activate cannabinoid receptors. Although adverse effects of cannabinoids on fertility have been implicated for years, the mechanisms by which they exert these effects were not clearly understood. With the identification of cannabinoid receptors, endocannabinoid ligands, their key synthetic and hydrolytic pathways, and the generation of mouse models missing cannabinoid receptors, a wealth of information on the significance of cannabinoid/endocannabinoid signaling in spermatogenesis, fertilization, preimplantation embryo development, implantation, and postimplantation embryonic growth has been generated. This review focuses on various aspects of the endocannabinoid system in male and female fertility. It is hoped that a deeper insight would lead to potential clinical applications of the endocannabinoid signaling as a target for correcting infertility and improving reproductive health in humans.

Role of lipids and lipid signaling in the development of cannabinoid tolerance

Cannabinoid agonists such as Delta9-tetrahydrocannabinol (THC) produce a wide range of pharmacological effects both in the central nervous system and in the periphery. One of the most striking features of cannabinoids such as THC is the magnitude to tolerance that can be produced upon repetitive administration of this substance to animals. Relatively modest dosing regimens are capable of producing significant tolerance, whereas greater than 100-fold tolerance can be obtained with aggressive treatments. While cannabinoid tolerance has been studied quite extensively to establish its relevance to the health consequences of marijuana use, it has also proven to be a valuable strategy in understanding the mechanism of action of cannabinoids. The discovery of the endocannabinoid system that contains two receptor subtypes, CB1 and CB2, associated signaling pathways, endocannabinoids (anandamide and 2-arachidonoylglycerol) and their synthetic and degradative pathways has provided a means of systematically evaluating the mechanism of cannabinoid tolerance. It is well known that the CB1 cannabinoid receptor is down-regulated in states of cannabinoid tolerance along with uncoupling from its second messenger systems. Endocannabinoid levels are also altered in selected brain regions during the development of tolerance. While it is reasonable to speculate that a likely relationship exists between receptor and endocannabinoid levels, at present, little is known regarding the biological signal that leads to alterations in endocannabinoid levels. It is also unknown to what degree synthetic and degradative pathways for the endocannabinoids are altered in states of tolerance. The discovery that the brain is abundant in fatty acid amides and glycerols raises the question as to what roles these lipids contribute to the endocannabinoid system. Some of these lipids also utilize the endocannabinoid metabolic pathways, produce similar pharmacological effects, and are capable of modulating the actions of anandamide and 2-arachidonoylglycerol. In addition, there are dopamine, glycine, and serotonin conjugates of arachidonic acid that may also contribute to the actions of endocannabinoids. A systematic examination of these lipids in cannabinoid tolerance might shed light on their physiological relevance to the endocannabinoid system.

Endogenous cannabinoid system as a modulator of food intake

The ability of Cannabis sativa (marijuana) to increase hunger has been noticed for centuries, although intensive research on its molecular mode of action started only after the characterization of its main psychoactive component Delta(9)-tetrahydrocannabinol in the late 1960s. Despite the public concern related to the abuse of marijuana and its derivatives, scientific studies have pointed to the therapeutic potentials of cannabinoid compounds and have highlighted their ability to stimulate appetite, especially for sweet and palatable food. Later, the discovery of specific receptors and their endogenous ligands (endocannabinoids) suggested the existence of an endogenous cannabinoid system, providing a physiological basis for biological effects induced by marijuana and other cannabinoids. Epidemiological reports describing the appetite-stimulating properties of cannabinoids and the recent insights into the molecular mechanisms underlying cannabinoid action have proposed a central role of the cannabinoid system in obesity. The aim of this review is to provide an extensive overview on the role of this neuromodulatory system in feeding behavior by summarizing the most relevant data obtained from human and animal studies and by elucidating the interactions of the cannabinoid system with the most important neuronal networks and metabolic pathways involved in the control of food intake. Finally, a critical evaluation of future potential therapeutical applications of cannabinoid antagonists in the therapy of obesity and eating disorders will be discussed.

Study of cannabinoid dependence in animals

Different animal models have been used to clarify the consequences of chronic exposure to cannabinoid agonists and their abuse liability. Following the chronic administration of cannabinoids, tolerance develops to most of their pharmacological effects. The development of cannabinoid tolerance is particularly rapid, and seems to be due to pharmacodynamic events. A cross-tolerance among different exogenous cannabinoid agonists has been reported. Somatic signs of spontaneous withdrawal have not been reported after chronic Delta(9)-tetrahydrocannabinol (THC) treatment, but were observed after chronic treatment with the cannabinoid agonist WIN-55,212-2. The administration of the CB(1) cannabinoid antagonist SR141716A in animals chronically treated with THC and other cannabinoid agonists precipitated somatic manifestations of withdrawal. The potential ability of anandamide to induce physical dependence has not been clarified. Subjective drug effects of cannabinoids have been reported by drug discrimination studies, which show cross discrimination among different natural and synthetic agonists. The rewarding effects of cannabinoids have been revealed by using several paradigms: place conditioning, intracranial self-stimulation, and self-administration. Cannabinoids have been reported to lower intracranial self-stimulation thresholds in rats. However, particular experimental conditions are required to induce conditioned place preference with cannabinoids. Numerous studies have shown that THC is unable to induce a self-administration behaviour in animals. However, WIN-55,212-2 was intravenously self-administered in mice, and monkeys that had a previous history of cocaine self-administration also self-administered THC. The mesolimbic dopaminergic system seems to be the substrate for the rewarding properties of cannabinoids.

Changes in body temperature after administration of antipyretics, LSD, delta 9-THC and related agents: II

Antipyretics, in particular acetaminophen, aspirin and ibuprofen, constitute the single most important class of drugs used therapeutically for an effect on body temperature. Hallucinogens exert prominent actions on the central nervous system, and it is not surprising that, like so many other centrally-acting agents, they too often affect temperature. This compilation primarily covers the considerable amount of data published from 1981 through 1985 on the interactions of these drugs and thermoregulation, but data from many earlier papers not included in a previous compilation are also tabulated. The effects of agents not classically considered as antipyretics on temperatures of febrile subjects are also covered. The information listed includes the species used, the route of administration and dose of drug, the environmental temperature at which experiments were performed, the number of tests, the direction and magnitude of change in body temperature and remarks on special conditions, such as age or brain lesions. Also indicated is the influence of other drugs, such as antagonists, on the response to the primary agent.

Models to predict cannabinoid-induced disturbances

The most commonly used animal models to evaluate the psychoactivity of cannabinoids have been reviewed. The need for suitable models is acute considering the present interest to develop drugs based on the cannabinoid moiety but preferably dissociated from psychoactivity. Conceivably, a satisfactory assay should show features of cannabinoid-induced disturbances relevant to man as well as sensitivity, specificity and simplicity. These requisites seemed better fulfilled in the monkey model. Various lines of evidence have demonstrated the close pattern of the behavioural response to psychoactive and inactive cannabinoids in man and monkeys. Rhesus monkeys showed development of tolerance and withdrawal symptoms, which have been frequently reported in humans after prolonged exposure to cannabinoids. The exposure was reported also to cause in monkeys alterations of electrical activity and organic damage in deep brain structures. The monkey model has been particularly useful to determine the relative potency of naturally occurring cannabinoids and metabolites, which was adequately compared to that in man, and to establish the structural requirements for psychoactivity in large series of synthetic new compounds. In addition it appeared that rhesus monkeys react similarly to man with respect to proposed antidotes against cannabinoids. Four newly synthetized amino-cannabinoids were tested in baboons. All these compounds were virtually void of typical cannabinoid psychoactivity but two trans-analogs differed from the cis-analogs in that they provoked bouts of vigorous scratching and yawning. This unusual drug-effect, at difference from scratching alone has not been previously observed after administration of cannabinoids. In this presentation some terms of cannabis terminology have been discussed.

Marihuana and sex: a critical survey

Marihuana usage is associated with a life-style that involves earlier and more frequent sexual activity. Marihuana usage does not affect human male testosterone levels significantly, but does adversely affect sperm production. Animal studies have not found consistent changes in weights of male sexual organs but have corroborated the adverse effects of cannabinoid compounds on sperm production. The biological significances of these effects on sperm production are unclear, however, since there is no evidence that human marihuana users or male animals given cannabinoid compounds are less fertile or are at risk for dominant lethal mutations. Cannabinoid compounds reliably inhibit ovulation in animals and are associated with depressed luteinizing hormone (LH) levels in both female and male animals. The decreased LH levels appear to be due to both hypothalamic and ovarian sites of action. Treatment with cannabinoid compounds is also associated with lower testosterone levels in male and lower prolactin levels in female animals. Effects on progesterone levels are inconclusive. Cannabinoid compounds do not possess estrogenic activity. Despite some consistencies in the data in virtually every study conducted with animals, there has been a basic confounding between direct drug action and secondary effects resulting from drug-induced decreases in food and water consumption and attendant weight loss. Almost all of the adverse effects of cannabinoid exposure on reproductive organs can be attributed to these secondary effects.

Cannabinoid-induced hormone changes in monkeys and rats

Previous findings at various laboratories indicated that cannabinoids distribute to sexual behavior centers in the brain, and endocrine aberrations have consistently been observed in animals treated with cannabis constituents. Subacute and chronic studies were performed to monitor hormone changes in rats and monkeys exposed to marihuana smoke or pure cannabinoids. In oral studies, young Fischer rats of both sexes were given delta 9-tetrahydrocannabinol (delta 9-THC) doses of 2, 10, or 50 mg/kg for 14--180 d and pregnant rats received 1, 5 or 10 mg/kg during gestation and lactation. Other male rats were exposed to marihuana smoke at delta 9-THC doses of 2 or 4 mg/kg for 14 d. Rhesus monkeys of either sex were given oral cannabidiol doses of 30, 100, and 300 mg/kg for 90 d. Serum pituitary, steroid, and thyroid hormone levels were determined by radioimmunoassay. Marihuana smoke (and oral delta 9-THC) depressed testosterone 20--30% and triiodothyronine 17--29%. In pregnant rats, small doses of delta 9-THC suppressed luteinizing hormone, but larger doses elevated both follicle-stimulating hormone and estrogens (approximately 50--100%) without affecting progesterone levels. Prolonged oral administration of delta 9-THC to young rats tended to increase gonadotropins, to which tolerance developed in males. Cannabidiol-treated monkeys responded with slight elevations in luteinizing hormone and follicle-stimulating hormone in males, whereas steroid hormones were essentially unchanged for both sexes. Hormone imbalance may explain cannabinoid-induced embryotoxicity and impaired gonadal function.

Muscular dystrophy in mice after chronic subcutaneous treatment with cannabinoids

Swiss male albino mice were treated subcutaneously with the main cannabinoids (CBN, CBD, delta9-THC) at the dosage of 1 mg/kg per day for 30 days, and with the crude resin. At the end of the treatment, after supramaximal stimulation of the sciatic nerve, a significant decrease of both maximal twitch and tetanus tensions was observed in delta9-THC-treated animals; CBD and resin treatment produced some decrease in active tension, while CBN treatment induced an enhancement of the contractile strength. Histology showed lesions interpretable as due to muscular dystrophy. Analysis of protein and hydroxyproline muscular content showed a marked reduction in protein in all treated animals, with a corresponding high increase in hydroxyproline content.

Toxicity of delta9 -tetrahydrocannabinol (THC) administered subcutaneously for 13 days to female rabbits

Delta9- Tetrahydrocannabinol (THC) was administered subcutaneously to female New Zealand white strain rabbits for 13 days. The animals were randomly divided into six groups of five animals each of which consisted of untreated controls, vehicle (undiluted propylene glycol)-treated, and THC treatment at dose levels of 100, 30, 10, and 3 mg/kg/day. All animals survived for the duration of the study. The THC-treated rabbits did not gain significant body weight which seems to be due to a decreased food consumption. There were some variations in various hematologic values, but they all were within the normal range for our laboratory. Blood chemistry evaluations showed decreased serum levels of potassium, glucose, blood urea nitrogen, alkaline phosphatase, and albumin/globulin (A/G) ratio and an increase in cholesterol levels of all treated animals. A significant increase in billirubin values was noted in the animsls of the 3- and 10-mg/kg groups. The injection site in the skin of the THC-treated rabbits showed signs of local irritation (erythema and subcutaneous abscesses). There was a reduction in absolute and percent of body weight of the liver and absolute weight of the lungs of the treated animals. However, no histopathologic alterations were observed. It may be concluded that THC treatment subcutaneously for 13 days in rabbits up to a dose level of 100 mg/kg/day did not produce any significant toxicity, except anorexia and some local dermal irritation.

Myeloid hyperplasia in growing rats after chronic treatment with delta 9-THC at behavioral doses

Delta 9-THC at the dose of 1 mg/kg/die was administered subcutaneously in growing rats, from the second to the 30th day of life. A statistically significant myeloid hyperplasia was demonstrated, which persisted up to 4 months after the end of the treatment, together with significant blood granulocytosis.

Versatile unit for filling gelatin capsules with drugs or chemicals

A new, inexpensive device was developed for making individually prepared capsules that can be administered to experimental animals. The device was designed for accurate and rapid production of large numbers of various capsule sizes and drug dosages. During 12 months of usage, 21 capsules were prepared weekly for each of 44 dogs (924 total capsules) in approximately 2.5 work-hours/week. Each capsule contained a precise amount of drug to administer a specific dosage to each individual dog. No difficulties were encountered in the manufacture or utilization of this device, and it can be operated by untrained personnel.

Effects of delta-9-tetrahydrocannabinol administered subcutaneously to rabbits for 28 days

Subcutaneous (s.c.) administration of delta-9-tetrahydrocannabinol (delta-9-THC) to rabbits produced dose-related cumulative toxicity. Five groups of three New Zealand albino rabbits each received 28 daily treatments with isotonic saline, sesame oil of 15.9, 45.0 or 153.4 mg/kg/day of delta-9-THC dissolved in sesame oil. Dose-related dermal responses included erythema, edema, ulceration and nodule formation. Some of the granulomatous nodules contained an oily substance and exhibited liquefactive necrosis. The severities of erythema and ulceration were generally maximal during the first week of treatment, but edema and nodule formation were most severe after days 12 and 14, respectively. All rabbits survived treatment, but body weights, liver weights and liver glycogen levels were decreased in a dose-related manner. Maximal body weight effects occurred after day 19. Hemochemical changes occurred only in rabbits treated with 153.4 mg/kg/day and included decreased blood sugar and alkaline phosphatase, and increased serum potassium. Hematology parameters were normal throughout the treatment period. No drug-related pathological lesions occurred in internal organs. The cumulative body weight changes, significantly decreased hepatic glycogen levels and reduced blood sugar and alkaline phosphatase values may have indicated drug-induced metabolic changes.