Cannabidiol (CBD) is a naturally occurring, non-psychoactive compound obtained from the Cannabis sativa plant, known for its potential in treating conditions such as pain, anxiety, inflammation, and epilepsy without causing the intoxicating effects linked to tetrahydrocannabinol (THC). It is one of more than 100 cannabinoids and produces its effects by interacting with the body’s endocannabinoid system. Initially isolated between the late 1930s and 1940, CBD’s chemical structure was later clarified in 1963 by Raphael Mechoulam and his team, which paved the way for further research in the 1970s demonstrating its anticonvulsant and anxiolytic properties. These discoveries ultimately led to the development and 2018 approval of Epidiolex for specific rare epileptic disorders. While CBD is generally well tolerated, it may produce side effects such as drowsiness, diarrhea, and decreased appetite, and it can interact with certain medications, including blood thinners and anticonvulsants; additionally, its legal status differs across regions, with many countries allowing hemp-derived CBD containing minimal THC while restricting products with higher THC levels.
BRAND NAMES
Epidiolex – the only FDA-approved prescription brand (for epilepsy).
Other cannabidiol products are sold under various non-standardized brand names (oils, capsules, creams), which vary by region and are not officially approved as medicines.
MECHANISM OF ACTION
Cannabidiol works mainly by interacting with the body’s endocannabinoid system, indirectly influencing CB1 and CB2 receptors. It also increases levels of natural cannabinoids by preventing their breakdown and affects serotonin and pain-related receptors, contributing to its calming, anti-inflammatory, and anticonvulsant effects.
PHARMACOKINETICS
Absorption
Cannabidiol has variable absorption, with low bioavailability when taken orally due to first-pass metabolism. Its absorption improves with fatty meals, while inhalation provides rapid uptake.
Distribution
After absorption, cannabidiol is widely distributed in the body and is highly lipophilic, meaning it concentrates in fatty tissues. Its volume of distribution (Vd) is approximately 32 L in adults, reflecting moderate tissue penetration. It also binds extensively to plasma proteins (about 94–99%).
Metabolism
Cannabidiol is primarily metabolized in the liver by cytochrome P450 enzymes, mainly CYP3A4 and CYP2C19. It undergoes hydroxylation and oxidation to form active and inactive metabolites, which are then further processed before excretion.
Excretion
Cannabidiol and its metabolites are mainly excreted via the feces, with a smaller portion eliminated in urine. The elimination half-life varies by formulation and route but is generally around 18–32 hours after oral dosing.
PHARMACODYNAMICS
Cannabidiol works by modulating the endocannabinoid system and interacting with serotonin and pain-related receptors. This produces its anticonvulsant, anti-inflammatory, anxiolytic, and analgesic effects without directly activating cannabinoid receptors.
DOSAGE AND ADMINISTRATION
Oral (Epidiolex): Typically started at 2.5 mg/kg twice daily and may be increased to 5 mg/kg twice daily based on response.
Administration: Can be taken with or without food, though high-fat meals improve absorption.
Other forms: Topical or inhaled cannabidiol products vary in dosage and are generally guided by product labeling, as standardized dosing is not established.
CONTRAINDICATIONS
Hypersensitivity to cannabidiol or any components of the formulation.
Severe liver impairment (caution advised due to hepatic metabolism).
Pregnancy and breastfeeding: Safety not well established.
Concurrent use with strong CYP3A4 or CYP2C19 inhibitors/inducers may require caution due to drug interactions.
DRUG INTERACTIONS
CYP450 interactions: Cannabidiol is metabolized by CYP3A4 and CYP2C19, so drugs affecting these enzymes (e.g., ketoconazole, rifampin) can alter CBD levels.
Antiepileptics: May increase levels of clobazam, valproate, or topiramate, enhancing effects or side effects.
Blood thinners: Can increase warfarin levels, raising bleeding risk.
Sedatives: May enhance CNS depressant effects when combined with alcohol or benzodiazepines.
FOOD INTERACTIONS
High-fat meals significantly increase absorption and plasma levels of cannabidiol, which can enhance both effects and side effects.
Taking CBD on an empty stomach may reduce its bioavailability and onset of action.
No specific foods are strictly contraindicated, but consistent meal patterns help maintain predictable drug levels.
SIDE EFFECTS
Common: Fatigue, diarrhea, decreased appetite, and dry mouth.
Less common: Nausea, vomiting, dizziness, and somnolence.
Rare but serious: Elevated liver enzymes, potential interactions with other medications, and hypersensitivity reactions.
OVER DOSE
drowsiness, diarrhea,
vomiting, and elevated liver enzymes.
supportive care
TOXICITY
Cannabidiol has a low toxicity profile. High doses may cause liver enzyme elevation, gastrointestinal upset, sedation, or drug interactions, but life-threatening toxicity is rare. Safety is generally good when used within recommended doses.
