Virginia Thornley, M.D., Neurologist, Epileptologist
May 8, 2018
Cannabinoids are being more and more widely used in a variety of neurological conditions. This always leads to the questions of side effects and will it interacts with other medications? Because this is wholly unchartered territory, in order to answer these questions, it is necessary to understand the underlying mechanisms.
Cannabinoids can cause tachycardia
Phytocannabinoids, when ingested, can induce tachycardia. The metabolism of cannabinoids by cardiomyocytes likely impacts the side effects elicited in cardiac cells. CYP2J2 is the most significant cytochrome p450 which metabolizes endocannabinoid anandamide (AE) into the cardioprotective epoxides. 6 phytocannabinoids were studied in one paper including delta-9-tetrahydrocannabinol, cannabinol, cannabidiol, cannabigerol, and cannabichromene. These were found to be metabolized more quickly compared to anandamide. The cannabinoids may potentially inhibit the metabolism of anandamide by CYPJ2 such that its effects are still circulating in the system. The most significant inhibition was from delta-9-tetrahydrocannabinol. It follows a non-competitive inhibition model such that the cardioprotective epoxides are not formed as abundantly as they should by the cytochrome p450 CYP2J2 (1).
The cytochrome P450 system has a significant impact on the metabolism of cannabinoids. Tetrahydrocannabinol is metabolized by CYP2C19 and CYP3A4. cannabinol is metabolized by CYP2C9 and CYP3A4. Synthetic cannabinoids include JWH-018 which is metabolized by CYP1A2 and CYP2C9 and AMC2201 which is metabolized by CYP1A2 and CYP2C9.
The cytochrome P450 enzymes are also thought to be involved in the metabolism of tetrahydrocannabinol. CYP2C9 greatly influences the metabolism of tetrahydrocannabinol. Cytochrome P450 3A4 is important in the metabolism of THC and CBD (2).
Cannabinoids in relation to hyperemesis syndrome
Once abdominal pain has been explored regarding medical etiologies, and there is a presence of 1-year history of cannabis use usually weekly, this diagnosis comes to mind. It usually involves cyclical vomiting associated with nausea. The mechanism is thought to be related to dysregulation by the endocannabinoid pathway in relation to the gastrointestinal tract. The CB1 receptor by which THC or tetrahydrocannabinol exerts it actions is also present in the GI tract. Exogenous cannabinoids may dysregulate the normal endocannabinoid pathway thereby affecting the GI tract through the down-regulation of the normal CB1 receptors so that it is no longer sensitive to endocannabinoids which regulate the system. This results in a dysfunction of the GI tract clinically manifested as cyclical nausea and vomiting. A disruption of the cannabinoid receptors may occur resulting in slowed motility of the gut. Relief can occur with use of hot water which influences the TRPV receptor a G-related coupled protein
- Arnold, et al, “Cross-talk of cannabinoid and endocannabinoid metabolism is mediated via human cardiac CYP2J2,” J. Inorganic. Biochem., 2018, Apr., 7(184):88-99 doi: 10.1016/j.jinorgbio.2018.03.016. (Epub ahead of print)
- Stout, et al, “Exogenous cannabinoids as substrates, inhibitors, and inducers of human drug metabolizing enzymes: a systematic review,” Drug Metab. Rev., 2014, Feb., 46(10:86-95.
- Lapoint, et al, “Cannabinoid hyperemesis syndrome: public health implications and a novel model treatment guideline,” West J Emerg Med, 2018, Mar., 19(2):380-386.
Virginia Thornley, M.D., Neurologist, Epileptologist
April 28, 2018
The Cannabis sativa plant has been known since the beginning of time. It can be traced back 5000 years ago when it was first known to man to alleviate common complaints. It came into the American pharmacopeia in the 19th century then abolished in the 1930’s, likely not coincidentally as the era of prohibition was lifted. It is known to treat ailments such as chronic pain and migraine. In the middle ages, it was used to treat headaches, vomiting, diarrhea, bacterial infections and pain from rheumatological conditions. It was previously known for its psychoactive properties. It is recently making a resurgence in popularity regarding its medical value. The issue is a topic of hot debate as state laws are at odds with federal laws. Currently, as of April 2018, it is still recognized as a category 1 drug, meaning it is not officially proclaimed to have any medical value despite the long rich history of treating medical symptoms. It is lumped in with other drugs of abuse such as heroin and cocaine.
Background on the Cannabis sativa plant and their metabolites
The Cannabis sativa plant is abundantly rich in phytocannabinoids, the most commonly known and used for its therapeutic value are cannabidiol and tetrahydrocannabinol. The endocannabinoid pathway is comprised of receptors that are coupled with G proteins and cannabinoids (1). In the Cannabis sativa plant, there are 80 phytocannabinoids that can bind to a cannabinoid receptor.
There are 8 major cannabinoids including cannabigerolic acid, delta-9-tetrahydrocannabolinic acid A, cannabidiolic acid A, delta-9-tetrahydrocannabinol, cannabigerol, cannabidiol, cannabichromene, and tetrahydrocannabivarin in the different strains of Cannabis sativa (1).
Ehlsoly, et al, classified it into 11 categories: cannabigerol, cannabichromene, cannabidiol, ∆9-trans-tetrahydrocannabinol, ∆8-trans-tetrahydrocannabinol, cannabicyclol, cannabielsoin, cannabinol, cannabinodiol, cannabitriol, and miscellaneous. ∆9 -trans-tetrahydrocannabinol , cannabinol, and cannabidiol are the most well-studied and well-known.
Cannabidiol is extracted from the hemp portion of the plant considered a male part of the plant, there are no psychoactive properties in cannabidiol. Psychoactivity is defined as anything above 0.3% of THC. Tetrahydrocannabinol is derived from the female portion of the plant, particularly the flowers. Conditions are such that in nurseries only a certain amount of sunlight is given to the plants so that specific strains can be grown. Some plants will be richer in cannabidiol, others will be more THC pure and other swill have an equal amount of CBD and THC but it depends on how the plants are grown and under what conditions.
It is through the endocannabinoid pathway that one gets the sense of well being after exercise or eating chocolate. It is not through endorphins, serotonin or noradrenergic neurotransmitters as they are too large to cross the blood-brain barrier. Tetrahydrocannabinol acts as a mimetic of Anandamide while cannabidiol acts as a mimetic of 2-Arachidinoylglyerol (or 2-AG). The endocannabinoid system works through cannabinoids, the receptors, transporters, and enzymes.
The phytocannabinoids work on cannabinoid receptors. The endocannabinoid system is mediated by 3 parts: the cannabinoids, the cannabinoid receptors, and the enzymes. The receptors are of 2 types, CB1 which is found primarily in the nervous system especially in the areas that subserve pain modulation, memory and movement. The CB2 receptor is more peripherally found specifically in the immune system. The CB2 receptor is found to a lesser extent in other organs including tissues of reproduction, pituitary, heart, lungs, adrenal and gastrointestinal systems. Cannabinoids also react with the TRPV receptor or the transient receptor cation channel subfamily V. They can also act on G receptors including GPR55 thought to be significant in controlling seizures. Other receptors include GPR12, GPR18, and GPR119 (2).
Tetrahydrocannabinol and cannabidiol and their effect on receptors
THC and CBD are the most well-known and well-studied. THC has psychoactive properties and works as a partial agonist on the CB1 receptor and the CB2 receptor. Cannabidiol which has no psychoactive properties works as an antagonist on CB1/CB2 receptor and an agonist on the CB1 and CB2 receptor. Rather than decreasing the effects of THC, it works in a synergistic manner in combination with THC. It potentiates the THC effects by increasing the CB1 densities. CBD increases vanilloid pain receptors, reduces metabolism and reduces re-uptake of anandamide, THC’s mimetic component. Other studies suggest CBD acts as an indirect agonist by interacting with the CB1 receptor so there are less psychoactive symptoms from THC when the two are combined.
Pharmacokinetics of tetrahydrocannabinol
Regardless of the way of taking it, the protein binding and the and volume of distribution are not affected by the route of taking it. Pharmacokinetics of creams and vaporizers are unclear. Smoking THC appears to exert an effect within minutes of intake and bioavailability is variable depending upon the extent of inhalation ranging between 2-69%. The effect is within minutes. Half-life increases with each inhalation at 2 puffs inhaled for THC it is 1.9 hours and 5.3 hours in CBD at 8 inhalations it is 5.2 hours in THC and 9.4 hours in CBD at a dosage of 5.4mgTHC/5.0mg CBD and 21.5mg THC/20 mg CBD respectively.
Oral routes may seem to be safer but have more adverse effects including GI symptoms such as nausea, vomiting, and diarrhea. Oral mucosal absorption is rapid within 15 minutes to 60 minutes. Oral tablets are lower in the rate of absorption at about 0.6 to 2.5 hours. The rate of elimination, when taken orally, is biphasic, initially occurring at 4 hours then 24-38 hours after ingestion.
There is much research ongoing on the mechanisms underlying the medical value of medical marijuana. It is now thought that cannabigerolic acid may have medicinal properties as well. So far, the most well-known and well studied are delta-9-tetrahydrocannabinol and cannabidiol. Most likely as research continues, greater value will likely be attributed towards the phytocannabinoids.
- Wang, et al, “Quantitative Determination of delta 9-tetrahydrocannabinol, CBG, CBD, their acid precursors and five other neutral cannabinoids by UHPLC-UV-MS,” Planta. Med, 2019, mar., 84 (4):260-266.
- Landa, et al, “Medical cannabis in the treatment of cancer pain and spastic conditions and options of drug delivery in clinical practice,”Biomed. Pap. Med. Fac. Univ. Palacky Olomouc Czech Repub., 2018, Mar; 162(1):18-25.