THC and Bioavailability
While it sounds decidedly nerdy and potentially foreign, bioavailability is a critical part of your experience and understanding of cannabis. Simply put, if you’re going to buy it or partake in it, don’t you want to experience ALL of it?
You may have perceived different effects when you smoke versus when you use tincture; in fact, you may have even noticed a difference when you eat an edible versus when you enjoy a few canna-gummies/candy. Good news, dear reader - you’re not crazy and you’re more of a budding connoisseur than you give yourself credit for! See what we did there?
Different methods of consumption will translate to different mechanisms for how the body absorbs those oh-so-desirable cannabinoids. So how do we make sense of bioavailability? And how do we use this knowledge to improve our experiences with cannabis?
Bioavailability is defined by the pharmacological community as the ‘quantity of unchanged substances appearing in blood plasma compared with intravenous application,’ i.e. administering a substance directly into a vein/veins. It can affect both the product’s potency and onset time, as well as determines how the body takes in, distributes, and eliminates the substance. How readily your body absorbs cannabinoids can be affected by numerous factors, including:
- Consumption method
- Extraction method;
- Physical and molecular structure of the substance
- Food and drug interactions
- Health conditions
- Circadian rhythm (aka your sleep cycles)
- Liver function
That’s a lot right!? And maybe, after all of that, you’re like, but all I want to do is have fun and feel good, to hell with the details. Well it’s your body, your choice, and your prerogative. We’re just here to cut through the noise, and pave the way for consumers to buy with confidence and dignity. It’s natural to feel a growing sense of overwhelm when taking on a wealth of new information. But not to worry, we will address them all over time and just give you little bits to chew on over time. So let’s start with the basics: How you’re consuming your cannabis
There are four key uptake systems from which the body can absorb cannabinoids: oral mucosal, ingestion, inhalation, and transdermal. For the purposes of this article we’re not going to go into detail about each and every cannabinoid; researchers have found that cannabis contains 480 different substances, 80 of which have been identified as cannabinoids. With this many unique molecules, we could easily write an encyclopaedia, so for the purpose of this article when we mention cannabinoids we’re referring to THC specifically.
The most common method of consumption, inhalation includes both smoking and vaping. The bioavailability of THC, CBD, and CBN fall within very wide ranges, with your body absorbing 10-35%, 15-45%, 10-65% of the molecules respectively. When we think of inhalation, we often only think of the lungs – the reality is that about 50% of THC is inhaled into the lungs, while the other 50% is lost by exhaling the inhaled amount. The amount makes it to the lungs is locally metabolized immediately, which is why you can feel the effects of your cannabis almost immediately. It’s important to note that while 50% of the smoke or vapor makes it to your lungs, the actual bioavailability of THC after inhalation is estimated to be 18%; when you vaporize cannabis instead of combusting it (i.e. smoking it) the estimated bioavailability increased to approximately 40%. Of the four uptake methods, inhalation has a relatively high absorption rate due to the high permeability of the lungs. Your lungs were designed to breath in oxygen, absorb this oxygen into the bloodstream via lung tissue, and exhale the carbon dioxide that is produced. We’re ultimately able to breath so well because of the lung’s large absorptive surface area and the direct absorption of a substance into the bloodstream. This large surface area and good blood supply is an efficient method of absorbing cannabinoids where they enter the circulatory system, bypassing the digestive system and skipping ahead to permeating the barrier between your brain and blood circulation.
This intake method of cannabinoids is comparable to the inhalation method in terms of bioavailability because much like the lungs, the mucous membrane under the tongue allows cannabinoids to enter the bloodstream in a quick and unaltered fashion. While there are three areas of the mouth that are made up of this absorptive mucosal tissue (under the tongue, the cheeks, and the roof of the mouth), the rates of absorption can vary in a significant way. To ensure the highest and fastest rate of absorption, it’s recommended to administer sublingual cannabis products underneath the tongue and give it a few seconds to be absorbed. Don’t worry though, even if you accidentally swallow them your body will still absorb the cannabinoids, you’ll just have to wait for them to be digested first. Sublingual administration of cannabinoids result in an incredibly high availability, around 50-75% in some cases! This saves time, money, and product since the higher bioavailability means it takes less product to feel the effects. The quick uptake time also reduces the risk of overconsumption and is perhaps the most medically beneficial way to ingest cannabinoids – with no lung irritation or risk of carcinogens, sublingual administration is a discrete and efficient option.
Edibles have been gaining popularity over the past few years – 13% of cannabis sales have been edible products! Ingestion simply refers to eating the cannabis product, and the bioavailability of eaten cannabinoids depends on two things: the efficiency of transporting the substance to the stomach to the intestine and on the metabolism in the liver. Your intestines and liver are responsible for absorbing and processing cannabinoids, which is why your wait time can take significantly longer and is more variable than other methods. From the stomach, fat cells containing cannabinoids are absorbed into the bloodstream (creating a “body high”) and carried to the brain (the “head high”). This process can take up to two hours to take effect and remains in the body well after the initial digestion of the product – this is where a person’s metabolism and liver health play a big role in the bioavailability of cannabinoids. Ingested substances have a bioavailability range of 4% - 12%, averaging around 6%, significantly lower than the bioavailability of the inhalation and sublingual method. Current research has found that the bioavailability of cannabinoids can be improved by the chemical makeup of the substance infused with cannabinoids (butter vs. coconut oil for example), as well as the foods you consume in conjunction with the edible, but there is still a lot of work to be done in this area.
By far the least utilized administration system, the delivery of cannabinoids applied topically has been woefully under researched, but presents interesting medical solutions. While THC’s ability to be absorbed through the skin is minimal at best, it has been found that the absorption of CBD and CBN is significantly different - these have been found to have almost a 10 fold increase in absorption rate compared to THC. This is possibly due to the molecular differences between THC, CBD, and CBN, but represents possible solutions of addressing acute and chronic pain in a non-psychoactive way. While more research is needed, CBD absorption transdermally has been found to reduce pain scores associated with multiple sclerosis, rheumatoid arthritis,
- Medicinal cannabis: Rational guidelines for dosing by Gregory T Carter 1, Patrick Weydt 2, Muraco Kyashna-Tocha 3 & Donald I. Abrams 4