As the wave of cannabis legalization sweeps North America, patients, the medical establishment, and adult use consumers are struggling to understand the science and sometimes nuanced efficacy of the medicinal molecules called cannabinoids that are produced by this natural herb. One of the most important yet misunderstood, topics regarding the consumption of cannabis is its bioavailability.
Bioavailability is defined by the degree and rate at which a substance (such as cannabis cannabinoids) is absorbed into the body of a human or is made available at the site of physiological activity. The topic of bioavailability becomes challenging based on the sometimes highly subjective efficacy of cannabinoids, such as cannabidiol (CBD) and tetrahydrocannabinol (THC) in the human body.
An ECS Primer
A proper understanding of the topic of the bioavailability of the constituent cannabinoids within cannabis requires basic knowledge of the underlying mechanism of how cannabinoids are absorbed by the body. Cannabinoids and terpenes are phytomolecules (meaning they are derived from plants like cannabis) that plug into special cellular receptors within a system called the endocannabinoid system (ECS).
The ECS features two types of cellular receptors: CB1 and CB2. The CB1 variety if found within the brain and central nervous system, whereas CB2 receptors are located in the glands and tissues of the immune system, including primary lymphoid organs such as the thymus and bone marrow and includes secondary lymphatic tissues such as the spleen, tonsils, lymph nodes, adenoids, skin, and liver.
The psychoactive cannabinoid THC, the most infamous and storied molecule within cannabis, is absorbed by CB1 receptors and, thus, allowed to cross the extremely selective blood/brain barrier.
Bioavailability by Consumption Avenue
Bioavailability is measured according to the availability of a drug or molecule within the bloodstream. Intravenously injected drugs are considered 100 percent bioavailable. Thus, the bioavailability of the medicinal molecules within cannabis varies considerably based on two primary factors: 1) consumption avenue and 2) individual efficacy.
Bioavailability can vary significantly from one patient or cannabis consumer to another. Individual characteristics such as age, gender, weight, overall health, and use of other medications all affect bioavailability, sometimes in a major way.
Many medical professionals prefer to administer cannabinoids such as THC and CBD via tinctures. Tinctures are concentrated liquid extractions of cannabis that are typically sublingually administered (via an eyedropper). Tinctures have a reputation within the medical cannabis community for providing the best bioavailability (better than smoking, vaporization, and even edibles).
It should be noted that a tincture can easily be consumed via two separate consumption avenues in the human body:
Sublingual (under the tongue).
Ingestion (stomach and liver).
Sublingual consumption features an onset of approximately 10 to 20 minutes, whereas ingestion and metabolization by the stomach and liver require 45 minutes to two hours for the onset of effects.
For decades, medical professionals and cannabis experts have advocated the use of vaporization, or vaping, instead of the smoking of cannabis flowers or concentrates for a variety of health reasons. Not only is the vaping of cannabis flowers or concentrates healthier because it produces no carcinogens, but also because it features an estimated 80 percent bioavailability.
Cannabinoids such as CBD and THC can be consumed via a wide variety of methods, all of which provide very different levels of bioavailability, as listed below:
Smoking: 30 percent bioavailability.
Suppositories: 50-70 percent bioavailability.
Tinctures: 40-50 percent bioavailability (when administered sublingually).
Vaporization: 80 percent bioavailability.
A 2015 research study entitled “Fatty Acid-binding Proteins are Intracellular Carriers for THC) and CBD” and published in The Journal of Biological Chemistry found that cannabinoids such as CBD and THC increase levels of the endocannabinoid (internally produced) anandamide (a molecule that is very similar in its efficacy to THC).
Concluded the researchers, “Recent reports suggest that CBD and THC elevate the levels of the endocannabinoid anandamide (AEA) when administered to humans, suggesting that phytocannabinoids target cellular proteins involved in endocannabinoid clearance.”
A 2005 study entitled “Pharmacokinetics of Cannabinoids” that was published in the journal Pain Research & Management found that “The variability of THC in plant material (0.3% to 30%) leads to variability in tissue THC levels from smoking, which is, in itself, a highly individual process. THC bioavailability averages 30%.”