Hepatotoxicity of a Cannabidiol-Rich Cannabis Extract in the Mouse Model

Laura E. Ewing, Charles M. Skinner, Charles M. Quick, Stefanie Kennon-McGill, Mitchell R. McGill, Larry A. Walker, Mahmoud A. ElSohly, Bill J. Gurley and Igor Koturbash

Molecules, 2019, 24, 1694

doi : 10.3390/molecules24091694


Abstract : The goal of this study was to investigate Cannabidiol (CBD) hepatotoxicity in 8-week-old male B6C3F1 mice. Animals were gavaged with either 0, 246, 738, or 2460 mg/kg of CBD (acute toxicity, 24 h) or with daily doses of 0, 61.5, 184.5, or 615 mg/kg for 10 days (sub-acute toxicity). These doses were the allometrically scaled mouse equivalent doses (MED) of the maximum recommended human maintenance dose of CBD in EPIDIOLEX® (20 mg/kg). In the acute study, significant increases in liver-to-body weight (LBW) ratios, plasma ALT, AST, and total bilirubin were observed for the 2460 mg/kg dose. In the sub-acute study, 75% of mice gavaged with 615 mg/kg developed a moribund condition between days three and four. As in the acute phase, 615 mg/kg CBD increased LBW ratios, ALT, AST, and total bilirubin. Hepatotoxicity gene expression arrays revealed that CBD dierentially regulated more than 50 genes, many of which were linked to oxidative stress responses, lipid metabolism pathways and drug metabolizing enzymes. In conclusion, CBD exhibited clear signs of hepatotoxicity, possibly of a cholestatic nature. The involvement of numerous pathways associated with lipid and xenobiotic metabolism raises serious concerns about potential drug interactions as well as the safety of CBD.

Keywords : cannabidiol; hepatotoxicity; liver injury; natural products; phytochemical

1. Introduction

Cannabidiol (CBD) is a non-psychotropic phytochemical present in Cannabis sativa that has gained significant popularity over the last decade. It is a major component of EPIDIOLEX®, a drug indicated for the treatment of drug-resistant epileptic seizures associated with Dravet and Lennox-Gastaut syndromes [1,2]. CBD has also been proposed as treatment for a number of other neuropsychiatric disorders for which clinical trials are currently ongoing [3].

CBD has also been marketed for a wide range of other indications, including ‘anti-cancer’, ‘anti-inflammatory’, ‘sleep promotion’, ‘relaxation’, ‘normal cartilage and joint function’, ‘antioxidant effects’, and ‘pain management’ just to name a few. The vast majority of those eects, however, were documented either in vitro or in clinical trials with equivocal results [4,5]. Apart from its purported salutary eects, accumulating evidence from pre-clinical in vivo studies and large-scale clinical trials, implies that CBD may elicit several potentially negative health outcomes. Specifically, numerous reports have demonstrated neurological, cardiovascular and reproductive toxicities subsequent to CBD use [6–14]. The authors of a large clinical trial that utilized CBD (dose regimen 2.5–30 mg/kg/day) to treat 278 patients with Dravet syndrome reported adverse events in 93% of subjects [15]. Another recent study inferred a strong genotoxic potential for CBD at concentrations commonly detected in human blood [16]. Furthermore, CBD may have a high drug interaction potential as it modulates numerous cytochrome P450 enzymes responsible for xenobiotic metabolism [17–21].

Of particular concern is the risk for CBD-induced hepatotoxicity [22]. Animal studies have reported increased liver weights in rhesus monkeys and elevated liver enzymes in dogs when CBD was administered at doses as low as 2 mg/kg of body weight [14,23]. In recent clinical trials, elevated liver enzymes were observed in 5–20% of patients treated with CBD, and a few patients were withdrawn due to the threat of fulminant liver failure [1,2,24].

The number of ‘CBD-containing’ products, available mostly online, is growing exponentially. However, the U. S. Food and Drug Administration (FDA) prohibits sales of CBD as a dietary supplement or food ingredient on the grounds that any ‘article’ that has been approved as a new drug or authorized for investigation as a new drug cannot be marketed as an ingredient in dietary supplements or conventional foods per the Food, Drug, & Cosmetic Act (FDCA) [21 U.S.C. §321()(3)(B) and 21 U.S.C. §331(II), respectively] [25]. Furthermore, a clear regulatory oversight exists which has led to an uncontrolled CBD market that, in turn, threatens the health of a trusting general public. For instance, in a series of tests performed by the FDA on a panel of ‘CBD-containing products’, a large fraction either did not contain the label-claimed quantity of CBD or they were contaminated with D9-tetrahydrocannabidiol (THC) [26]. Furthermore, a recent independent analysis performed by CosumerLab.com, revealed that CBD doses in commercially-available products ranged from as little as 2.2 mg to as much as 22.3 mg, further amplifying concerns of potential toxicity [27].

As expansion of the CBD market seems inevitable, additional scientific studies are needed in order to support any required regulatory actions. For instance, if CBD is to be considered as a food additive, it will have to be filed as a new dietary ingredient (NDI) or a GRAS (generally recognized as safe) notice will need to be submitted to FDA. The latter will require a number of toxicity studies, the majority of which, in the case of CBD, remain to be performed. Analysis of genotoxic potential of CBD, the first toxicity test recommended by the FDA, was recently performed and the results published [16]. Therefore, we proceeded to the next set of recommended tests designed to address the short-term toxicity of a CBD-rich extract in a rodent model. Since liver injury is the primary concern for CBD, this study was designed to investigate the hepatotoxicity potential of CBD. The data collected in this study will provide important information for both industry and regulatory agencies in regards to the short-term toxicity of CBD. Furthermore, the results of these studies will aid in selecting appropriate models and doses for long-term studies (i.e., sub-chronic and chronic toxicity as well as carcinogenicity and reproductive toxicity studies) as well as the determination of a no observable eect level (NOEL) for selected endpoints.

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