Therapeutic cannabis administration is increasingly used in Western countries due to its positive role in several pathologies. Dronabinol or tetrahydrocannabinol (THC) pills, ethanolic cannabis tinctures, oromucosal sprays or table vaporizing devices are available but other cannabinoids forms can be used. Inspired by the illegal practice of dabbing of butane hashish oil (BHO), cannabinoids from cannabis were extracted with butane gas, and the resulting concentrate (BHO) was atomized with specific vaporizing devices. The efficiency of “cannavaping,” defined as the “vaping” of liquid refills for e-cigarettes enriched with cannabinoids, including BHO, was studied as an alternative route of administration for therapeutic cannabinoids. The results showed that illegal cannavaping would be subjected to marginal development due to the poor solubility of BHO in commercial liquid refills (especially those with high glycerin content). This prevents the manufacture of liquid refills with high BHO concentrations adopted by most recreational users of cannabis to feel the psychoactive effects more rapidly and extensively. Conversely, “therapeutic cannavaping” could be an efficient route for cannabinoids administration because less concentrated cannabinoids-enriched liquid refills are required. However, the electronic device marketed for therapeutic cannavaping should be carefully designed to minimize potential overheating and contaminant generation.
The creativity of cannabis users leads to new methods of consumption. Although developments such as vaporizers, edible and liquid tinctures have become very popular alternatives to the traditionally smoked flower buds of cannabis, they show flaws in concentrations, contamination or efficiency over the day according to galenic forms1. Recently, consumption methods such as butane hashish oil (BHO, cannabis concentrate extracted with butane gas) called “dabbing”, have been increasingly observed2,3,4, especially on Web fora. By eliminating tobacco and increasing THC levels, these optimizations appear to be interesting improvements for the therapeutic use and delivery of cannabis. However, public health concerns remain because of the ease of preparation, more rapid THC delivery (i.e., a potentially higher risk of dependence) and overdose5,6.
Dabbing involves vaporizing cannabis concentrates (BHO or cannabis dabs) at 300–400 °C on a hot surface and then inhaling the vapor through a specialized pipe7,8. BHO is a viscous, sticky to hard, wax-like concentrate that contains mainly acid cannabinoids and terpenoids. After thermal treatment, inactive tetrahydrocannabinolic acid (THC-A) is decarboxylated into psychoactive tetrahydrocannabinol (THC). BHO is highly enriched in THC, and its concentration is typically 15 to 30 times higher than that found in flower buds4. However, the literature is very scarce concerning BHO preparation and composition. Commonly, a dab of the dense oil is placed on the end of a glass or titanium rod that has been heated. If the dab has been previously decarboxylated, the flame from a lighter is sufficient to vaporize the BHO, but if the dab has not been decarboxylated, a blowtorch is used to maximize the decarboxylation of THC-A into its psychoactive form, THC, and to vaporize the BHO concentrate1.
Nevertheless, the enormous growth and development of electronic cigarettes (or e-cigarettes) have enabled the development of electronic devices exclusively dedicated to direct dripping (the liquid is dripped onto the bridge of the atomizer, instead of relying on the cartridge filler)9 and dabbing. These devices are currently available on the Internet and cannabis derivatives shops. Furthermore, a profusion of recipes is available on the Internet to prepare liquid refills enriched with cannabinoids. In this regard, BHO can be dissolved in the commercial liquids used to refill e-cigarettes, constituting an alternative to direct BHO dabbing. With the several thousand flavored liquids commercially available, flavors added to liquid refills can mask the overwhelming typical odor of cannabis and can make its vaping more discreet10. Indeed, concentrating cannabinoids implies a concentration of terpenoids and odorant compounds, which renders dabbing an easily detectable method of cannabis consumption for people exposed passively to cannavaping. Other recipes mention mixtures of solvents and flavors elaborated according to home-made protocols, including the dissolving of BHO in various propylene glycol/glycerin mixtures1, sometimes with the addition of edible or aromatic oils such as coconut or cinnamon. This new method of cannabis consumption could be called “cannavaping”. Thus, “cannavaping” and BHO dabbing could be considered major risks of electronic device misuse mainly because of the uncontrolled cannabinoids compositions of liquid refills and dabs. Nonetheless, “cannavaping” (of liquid refills) with controlled cannabinoids compositions and concentrations offers a new opportunity to deliver therapeutic cannabis without the requirement of smoking. The regulations of European countries have recently registered positive concern with the therapeutic use of cannabinoids11. By November 2014, a total of 23 states in the U.S. had enacted laws legalizing medicinal use3.
Nevertheless, the possibility of e-cigarette multiuse for cannavaping has arisen, whereas the carbonyls and volatile toxic compounds in the vapors of conventional e-cigarettes are still discussed12,13,14,15. The multiple designs and settings at users’ disposal could lead to significant toxic compound levels even if it requires high settings, causing burnt off-flavors generally not appreciated by usual vapers, defined as vaping devices users16,17,18,19,20. Indeed, to increase the decarboxylation rate of inactive cannabinoids acids (in case of misuse), cannavapers need to use high power settings (by using high voltage and/or low ohmic resistance atomizers). Regular cannabis smokers will prefer e-cigarette aerosols with strong organoleptic qualities. Moreover, the unpleasant flavors of liquid refills heated at such high settings could be hidden by the strong flavor of cannabis terpenoids. Consequently, the investigations of e-cigarettes vapors should always consider carbonyls and volatile compounds monitoring. Although concerns about the generation of contaminants from glycerin and propylene glycol are well identified, other concerns that have received little attention until now include the potential for toxic effects from inhaled flavorings21.