CBD, cannabidiol, is a type of cannabinoid found in hemp and marijuana. It is non-psychoactive, meaning it doesn’t produce the “high” that THC, another cannabinoid found in marijuana, does when taken medicinally or recreationally. CBD is currently being used widely as an effective treatment for chronic pain for patients with conditions such as joint pain, withdrawal symptoms, or cancer.
In order to get the desired effects of these cannabinoids, users have multiple options for its delivery method. Topical ointments, transdermal patches, tinctures, edibles, nasal sprays, smoking, and vaporizing are all viable methods or products for delivering CBD into the body. However, there are pros and cons to each method, differing in the overall effectiveness and desired treatment result.
Cannabinoids are lipophilic molecules, meaning they are able to dissolve in fats, but not in water. Therefore, they are not readily absorbed by the body when eaten directly (Cherniakov 2017). Normally, CBD and THC are dissolved into fats that humans can digest such as seed oils. They can also be baked into foods that containing butter. In this form they can be metabolized more readily by the body, but the absorption rate still only ranges from 6-15%. Another cause of this low absorption is due to what is known as the “first-pass metabolism”. Compounds that are digested by the stomach then pass through the liver before they enter the bloodstream. This contributes to their reduced effectiveness because enzymes in the liver breakdown a portion of cannabinoids before they are able to be absorbed by the body (Lodcki 2003). Many products contain emulsifying and absorption agents which serve to increase the bioavailability once ingested. When CBD and THC are consumed orally, it usually takes 1-2 hours before the consumer can feel the effects. However, it has a very long duration because the body processes it slowly. Oral usage of cannabinoids is effective for people looking for long-term effects and widespread pain.
Tinctures are alcohol based extractions of cannabinoids that can be consumed sublingually, meaning under the tongue (Notcutt 2004). Depending on the strength of the tincture, a few drops will allow absorption into the bloodstream with a faster, stronger onset than edibles. The CBD absorbs directly into the capillaries and mucus membranes of the mouth, bypassing the first-pass liver metabolism.
CBD can be smoked, from the flowers of marijuana, or vaporized, from oil concentrates. Smoking is commonly associated with recreational use instead of medicinal due to its adverse health effects on the lungs, as well as its social stigma. Smoking, by far, has the highest rate of absorption and fastest onset because it is absorbed directly into the bloodstream from the alveoli of the lungs, and is quickly spread in the bloodstream to the brain and throughout the body. Some studies show up to 56% CBD and THC absorption from smoking or vaporizing. Using whole plant or oil vaporizers greatly reduces carcinogen intake because it does not combust (Abrams 2007)(Heustis 2007). Electronic cigarettes or dab rigs can be used to vaporize cannabis oils to achieve the effectiveness of inhaling cannabinoids without carcinogens. However, the health risks of vaporizing cannabis extracts have not been studied fully and have been found to have irritating effects on the lungs.
Topical products are popular in treating localized skin, muscle, or joint pain. Transdermal patches, similar to those that deliver nicotine, are also available for very slow and controlled release of CBD. They are useful for maintaining stable amounts of CBD in the body for days at a time because of their slow and constant release method (Brooke 1997). All absorption methods work in similar ways by penetrating the surface skin and the muscles beneath. Because cannabinoids are fat soluble, they accumulate in the skin and surface tissues and do not have a strong ability to penetrate further. CBD is combined with penetration enhancers, such as ethosomes, to make these topical products more effective (up to about 45% absorption). Ethosomes allow medications to move between cells more readily by mimicking molecules that already exist in the body (Lodcki 2003).
Intranasal products, those inhaled through the nose, are being developed as a fast-acting delivery method that could be widely accepted as an alternative for smoking or vaporizing. Tests have shown this method to have absorption rate of 34-46%. Also, sprays have demonstrated a more immediate and stronger effectiveness than other methods because it is absorbed directly into the bloodstream through the mucus membranes in the nasal passages. Nasal sprays also have the advantage of being fast acting without any negative effects on the lungs caused by smoking or vaping (Paudel 2010) or the social stigma of smoking.
Currently there is very little research detailing the comparative efficacy of different cannabinoid delivery methods. Many of these studies were done in small mammals like mice, and have not gone into human trials yet. THC has been studied in much more detail, although in general, it is essentially absorbed the same way as CBD since they are molecularly and biologically similar. As the medicinal and recreational marijuana industries grow, more research will be conducted on CBD and its effectiveness in different modes of delivery.