Jared D. Hoffman, PhD

Cannabidiol, or CBD, is one of many cannabinoids found in cannabis (also known as hemp) that’s popularity and scientific backing has been growing with studies now showing its safety and efficacy in numerous disease states such as epilepsy, anxiety, and pain management. Indeed, CBD is a potential therapeutic tool with clinical trials currently ongoing in a variety of diseases.^{1, 2}With this rise in popularity, a plethora of different ways to take CBD have hit the market. These methods of delivery may be products that contain just CBD, such as CBD oil, or a combination of CBD with tetrahydrocannabinol (THC), also a cannabinoid and the psychoactive component of cannabis that produces the high we associate with the plant.

The primary methods of delivery include oral digestion, sublingual (placing it under the tongue), oromucosal sprays, applying it on the skin (subtopical or transdermal), and inhaling it. Each method is different in how quickly their effects begin, how long the experience lasts, and how great of an effect there is. One’s genetics and medications can also impact these factors although a review in 2014 concluded that CBD has a low risk of clinically significant drug interactions.³ Nevertheless, one should check with their physician when considering taking CBD alongside their medications.

The duration of the effects that CBD produces can last at least 3 hours, but more research needs to be conducted as studies have found a wide range of time. It is believed that the method of delivery can further impact the duration of effects.² Due to this and the differences in people’s preferences and reason for using CBD, each person will need to experiment and decide which of the following methods of delivery works best for them.

Oral Ingestion:

Orally ingesting CBD can be done through pills or capsules, swallowing CBD oil, or mixing the CBD with food or drink. Depending on what the CBD is mixed with and how much food is in the individual’s stomach, the duration of onset could take up to a couple of hours. Also due to the CBD having to pass through the entire digestive system, many of the active ingredients may not actually make it to the bloodstream and exert an effect. Animal research suggests the bioavailability of CBD is indeed low with only 13-19% being absorbed.⁴ At this point, little research in humans is available to confirm this. Further, CBD is lipophilic, so it has been suggested that consuming or mixing CBD with a fat source may increase bioavailability.¹ Despite the lack of research on the bioavailability of CBD, it is now being infused with a variety of products on the market. These include coffee, tea, protein bars, candy, a variety of supplements, and even restaurants that are now including CBD-infused food to their menus.

Sublingual (Under the tongue):

The sublingual method involves putting drops of CBD under the tongue, holding it there for up to a couple of minutes, and letting it absorb through your tongue and into the bloodstream. This is a quicker acting method of delivery than oral ingestion with effects taking hold in as little as a few minutes. Thus, this would be ideal for those in need of acute symptom relief. This and oral digestion are the more common and accessible methods of delivery for taking CBD oil.

Oromucosal Sprays:

Oromucosal sprays, aerosols, and nebulizers are other methods of delivery. This is also a quick acting method of delivery as CBD is sprayed up the nasal cavity or into the mouth and rapidly inhaled into the lungs. Another thing to keep in mind is that being in the fed state appears to help increase bioavailability compared to being fasted when using oromucosal sprays.⁵

On the skin (Subtopical or Transdermal):

Rubbing the CBD on the skin to be absorbed through the pores is another common method of delivery with a variety of different lotions, creams, and other topicals mixed with CBD now hitting the market. This method may take up to an hour to have any effects and it may not even reach the bloodstream. Transdermal patches are a similar method but are typically designed to release a specific amount of CBD in the bloodstream over a multiple hour period of time. This method of delivery may be best for those using CBD for skin and joint issues due to the lack of evidence that CBD is indeed able to reach the bloodstream through the skin.

Inhaling:

Inhaling CBD by smoking cannabis is the quickest method of delivery, with effects potentially taking hold in seconds, and a common method among recreational drug users that desire the psychoactive effects of THC. This is the ideal method for those needing immediate pain and symptom relief. The effects typically last for 2-3 hours. This method also makes it easy for someone to figure out their optimal dose due to the onset of action being so short. However, one negative is that smoking may be harmful to the lungs. For those not in need of THCs effect, vaping the CBD oil itself is another option that may not be quite as quick acting as smoking but may actually be a more efficient way of getting CBD to the bloodstream.

Other methods:

Other less common and accessible methods that have limited scientific research include intravenous, rectal, and intraperitoneal administration. These methods may provide very acute effects but are not as accessible to most people as the previously mentioned methods.

Overall, there are numerous ways to take CBD. Each individual will need to figure out what works best for them based on their preferences, reason for using CBD, genetics, whether or not they are on other medications that could potentially interact with CBD, and if they also want the psychoactive effects of THC. In the future, more scientific literature should be available, as clinical trials utilizing CBD are ongoing, to get a better idea of the bioavailability of CBD with these different methods of delivery.

References:

1. Bergamaschi,M.M., Queiroz, R. H., Zuardi, A.W., and Crippa, J. A. Safety and side effects of cannabidiol, a Cannabis sativa constituent. Curr. Drug Saf. 2011; 6:237–249.

2. Millar SA, Stone NL, Yates AS, O’Sullivan SE. A Systematic Review on the Pharmacokinetics of Cannabidiol in Humans. Front. Pharmacol. 2018; 9:1365.

3. Stout, S. M., and Cimino, N. M. Exogenous cannabinoids as substrates, inhibitors, and inducers of human drug metabolizing enzymes: a systematic review. Drug Metab. Rev. 2014; 46:86–95.

4. Mechoulam, R., Parker, L. A., and Gallily, R. Cannabidiol: an overview of some pharmacological aspects. J. Clin. Pharmacol. 2002; 42:11S−19S.

5. Stott, C. G., White, L., Wright, S., Wilbraham, D., and Guy, G. W. A phase I study to assess the single and multiple dose pharmacokinetics of THC/CBD oromucosal spray. Eur. J. Clin. Pharmacol. 2013; 69:1135–1147.