The avalanche of CBD products and brand choices now inundating the marketplace can be overwhelming. It seems like every one of the thousands of CBD providers offers the best, most effective and most local products. While it’s impossible to evaluate every option, we can start with considering: what does science say about the various modalities of consumption?
In general, the most common categories of CBD consumption are: oral, sublingual, topical, and inhalable (smoke or vapor). Ranking the overall body of scientific study directed at these routes of administration, the oral and sublingual methods are the most well studied. While these two routes are not equivalent since oral consumption is at least partially subject to first-pass metabolism, they are both surefire ways to elevate your blood plasma CBD levels. In general sublingual is a more rapid route for CBD absorption, but oral consumption, especially when combined with a large meal, can potentially produce longer lasting sustained blood levels of CBD.
Due to the history of cannabis use, there are some published studies on smoking that include assays of CBD pharmacokinetics. While smoking is a well-established method to deliver cannabinoids to the bloodstream, it is also known to produce harmful by-products. In a 2019 review article, Taskin and Roth conclude that while the long term pulmonary effects of habitual cannabis smoking are unclear due to a lack of properly controlled clinical studies, the carcinogenic and respiratory toxin profile of cannabis smoke is similar to that of tobacco smoke. Although most people are not smoking as much cannabis as a habitual tobacco smoker is smoking tobbaco, the average cannabis smoker’s per puff exposure to gases and tar is actually higher than the typical tobacco smoker. Overall the data suggest that caution is warranted when inhaling smoke from any source.
Vaporization is a broad category of methods that attempt to heat cannabinoids like CBD to their vaporization point, making them inhalable, but below the point of combustion to possibly avoid some of the harmful by-products found in smoke. These methods offer both promise for rapid delivery of CBD but also concern that harmful by-products may be co-delivered even without the combustion process taking place. The higher the temperature used to vaporize, the more likely chemical reactions will take place, potentially producing unwanted compounds. In their 2017 research paper, Meehan-Atrash et al., found considerable levels of the toxicants methacrolein and benzene, likely produced by the pyrolysis of myrcene (a common cannabis terpene) at higher vaporization temperatures. While this study used higher temperatures (400 to 500 C) than is necessary to vaporize CBD, it none the less underscores what happens when you heat large organic molecules–they may break apart and change their configuration. Keep in mind that smoking cannabis (or tobacco) produces temperatures around 900 C.
Topical (aka transdermal) administration of CBD is the least studied of the typical delivery methods but shows some promise according to a few studies. For example in a 2015 study conducted by researchers at the University of Kentucky College of Medicine, topical CBD gel applied to mice with arthritic knee joints was found to have “significantly reduced joint swelling, limb posture scores as a rating of spontaneous pain, immune cell infiltration and thickening of the synovial membrane in a dose‐dependent manner”. A previous in vitro human tissue study by this same research group published in 2004 found that CBD had good transdermal delivery potential, and most interestingly that addition of ~30% ethanol significantly increased CBD transdermal flux. This shows that while CBD can likely be effective as a topical application, adding compounds that increase the permeability of human skin will increase the overall efficiency of this approach.
In conclusion, CBD can effectively be consumed via many routes: orally, sublingually, inhalation and through your skin. Direct comparison among these approaches is an ongoing research topic with many open questions in regard to pharmacokinetics and health outcomes. Consider the long half life of CBD (estimated at 18 – 60 hours) when designing your personal regimen, and keep in mind that dosage information found via search engines and product packaging should be viewed as very general guidelines only. If you are considering trying CBD for the first time, or are in the process of developing a personal regimen, start your dosages low and work your way up incrementally to find a minimally effective dosage. Finally if you are a daily or weekly consumer, regularly scheduled intervals without CBD consumption, even if only at the scale of 48-72 hours, may improve your sensitivity to CBD–keeping your costs down and helping you feel your best.
Tashkin D. & Roth M. (2019) Pulmonary effects of inhaled cannabis smoke, The American Journal of Drug and Alcohol Abuse, 45:6, 596-609, doi: 10.1080/00952990.2019.1627366
Hammell, D., Zhang, L., Ma, F., Abshire, S., McIlwrath, S., Stinchcomb, A. and Westlund, K. (2016), Transdermal cannabidiol reduces inflammation and pain‐related behaviours in a rat model of arthritis. Eur J Pain, 20: 936-948. doi:10.1002/ejp.818
Stinchcomb, A.L., Valiveti, S., Hammell, D.C. and Ramsey, D.R. (2004), Human skin permeation of Δ8‐tetrahydrocannabinol, cannabidiol and cannabinol. Journal of Pharmacy and Pharmacology, 56: 291-297. doi:10.1211/0022357022791
Meehan-Atrash J., Wentai L., and Strongin R. M. (2017) Toxicant Formation in Dabbing: The Terpene Story. ACS Omega, 2:9, 6112-6117. doi:10.1021/acsomega.7b01130