Bioavailability of cannabinoids – suppositories (6/6)

Bioavailability of cannabinoids – suppositories (6/6)

Rectal administration is rare. One of the possible reasons for this is that the research concludes so far that THC administered rectally is not absorbed into the bloodstream [1,2]. Some success (absorbance levels of 10-70% depending on the formulation and animal tested) has been reached with using synthetic THC derivatives [3-6]. Such results can explain why most of the user would not experience “high” after administrating THC per rectum (at least as in comparison with other methods of administrations).

There are no available studies on absorbance of either hemp extracts or cannabinoids other than THC after rectal administration. However, due to the fact that the whole family of cannabinoids exhibits fairly similar physicochemical properties to THC, it may be presumed that rectal administration is, in general, not an efficient method of administration. In effect, obtaining the same pharmacological effect requires a much larger dose than other methods of administration (which, given the price of the preparations, is not too economical).

Rectal administration should not be confused with intravaginal administration (and this is not only a good tip to improve your sex life). For the latter, there are THC- and CBD-based supplements available that are recommended for menstrual pain. In this case some local activity of THC is not impossible, although there is no evidence of the effectiveness of such measures. There is, however, one publication on effects of CBD-containing suppositories in treating the symptoms of colitis in mice [7].

I realize that using suppositories has become, weird as it seems, a kind of a fashion in Poland, unfortunately, the particular effectiveness of this method of administration has not been confirmed in the scientific literature. Moreover, due to the mess in cannabinoid research and the lack of understanding of their actual results, many myths are emerging, which are then reproduced in pseudoscientific studies or on websites of sellers who catch up with good sounding passwords. A great example of this is the table of bioavailability reproduced extensively in various commercial sources, such as the website of Endoca [8]:



Figure 1: Comparative bioavailability of various cannabinoids of different administration routes.

The purpose of this table is of course to boost the sales of hemp extract-based suppositories containing CBD. Everything would be fine if not for the fact that the table had undergone some “cosmetic” changes. I found another version of the same table on a different webpage [9]:

It turns out that the table shows not the bioavailability of cannabis extract, but only this of the synthetic compound – , a compound which has absolutely nothing to do with natural cannabinoids and the extract at hand does not even contain it! In effect, the results of this test cannot by any means be applied to natural cannabinoids, not to mention the extracts! Moreover, according to the publication quoted as the source [4], the results of the 60-70% bioavailability (in plasma) were achieved with dogs, while with the monkeys they barely reached the range of 10-15% (which is indeed higher than obtained with administrating the succinic orally, but THC- HS was selected for this study specifically to demonstrate a better performance of suppositories. In fact, the succinate-THC was synthesised in the first place exactly in reaction to the results of other studies showing no bioavailability of natural THC administered as suppositories [10].

PhD, Eng. Beata Plutowska

References:

[1] Information for health care professionals: Cannabis (marihuana, marijuana) and the cannabinoids (February 2013) Health Canada
[2] Perlin, E., Smith, C.G., Nichols, A.I., Peck, C.C. Disposition and bioavailability of various formulations of tetrahydrocannabinol in the Rhesus monkey. Journal of Pharmaceutical sciences 74 (1985) 171-174.
[3] Huestis M., Smith M.L. Cannabinoid pharmacokinetics and disposition in alternative matrices. Handbook of Cannabis, Ed. R.G. Pertwee, Oxford Uniwersity Press (2014) Oxford, United Kingdom, 296-313.
[4] Walker, L.A., Harland, E.C., Best, A.M., ElSohly, M.A. ?9-THC hemisuccinate in suppository form as an alternative to oral and smoked THC. Marihuana and medicine, Ed. Nahas G.G., Sutin K.M., Harvey D., Agurell S., Pace N., Cancro R., Humana Press Inc. (1999) Totova, NJ, 123-135.
[5] Mattes R., Engelman K., Shaw L.M., Elsohly M.A. Cannabinoids and appetite stimulation. Pharmacology Biochemistry and Behavoiur, 49 (1994) 187-195.
[6] Elsohly M.A., Little, Jr. T.S., Hikal A., Harland E., Stanford D.F., Walker L. Rectal bioavailability of delta-9-tetrahydrocannabinol from various esters. Pharmacology Biochemistry & Behaviour 40 (1991) 497-502.
[7] Schicho R., Storr M. Topical and systemic cannabidiol improves trinitrobenzene sulfonic acid colitis in mice. Pharmacology 89 (2012) 149-155.
[8] https://www.endoca.com/Endoca_SUPPOSITORIES-21-CBD_Suppositories_Total:500mg_CBD_0
[9] http://cannabisdigest.ca/cannatory/
[10] Perlin, E., Smith, C.G., Nichols, A.I., Peck, C.C. Disposition and bioavailability of various formulations of tetrahydrocannabinol in the Rhesus monkey. Journal of Pharmaceutical sciences 74 (1985) 171-174