Suppositories are a popular method of cannabis administration and can be effective at treating some conditions and disease. However, information available on healthcare forums, blogs, and social media posts include prevalent misconceptions about the efficacy of suppositories and erroneous interpretations of the existing research. The following information should enable patients to make more informed decisions about which delivery method is best to treat their condition.
During rectal administration, fluids are absorbed by the rectum's blood vessels and are mostly directed into the body's circulatory system, which distributes the fluid to the organs and bodily systems. Typically, a drug that is administered rectally has a faster onset, a higher bioavailability, a shorter peak, and a shorter duration than when the same drug is administered orally.
This route of administration partially bypasses first-pass metabolism. The rectum's venous drainage is two-thirds systemic (consisting of the middle and the inferior rectal vein) and one-third hepatic (the superior rectal vein). Drugs administered rectally typically reach the blood stream with significantly less hepatic alteration.
Multiple factors affect the absorption rate of rectal medications, including molecular size, water-solubility, depth of insertion, dehydration, low surface area, and the base of a suppository preparation. Additionally, absorption rates of suppositories are slower than that of other delivery methods and the rate at which suppositories absorb is largely dependent on chemical additives in the suppository.
Currently, there is some debate about whether rectally administered cannabis can effectively treat conditions that affect the entire body. Commonly-referenced research states that rectal absorption rates of cannabis are as high as 50-70%. In these studies, however, delta-9-THC was coupled with an ester hemisuccinate, which is an additive designed to increase absorbency by breaking down fat-soluble compounds into water-soluble compounds.
Other studies designed to test rectal absorption of cannabis demonstrated that, without hemisuccinate, rectal absorbency was 3% or less. In fact, there exists some general agreement that fats and oils are poorly absorbed from the rectum. Cannabinoids are lipids (fats) and cannabis products are nearly always extracted into an oil or fat base, so it reasonable to assume that whole plant cannabis oil products are poorly absorbed rectally. And, because most preparations of cannabis suppositories do not contain hemisuccinate, it is safe to assume that most of these preparations are not being adequately absorbed.
Some medical practitioners and cannabis manufactures suggest that rectal administration is advantageous because patients can take larger doses while avoiding psychoactivity. However, cannabinoids absorbed through the rectum should flow into the blood stream through one of two possible routes:
Pass into the middle and the inferior rectal veins and eventually flow into the blood stream.
Pass into the superior rectal vein and through the liver circulation (where they are metabolized by enzymatic processes) and eventually flow into the blood stream.
In both routes, there should be detectable levels of THC in the plasma and those levels should correspond to a discernible psychoactivity. The reason no psychoactivity is reported is that the cannabinoids have not been adequately absorbed into the bloodstream. Patients who use high THC products through rectal administration and who fail to feel any psychoactive side effects are likely not improving any systemic issues.
Of course, patients have reported that they have successfully treated conditions and disease with cannabis suppositories, but there may be other factors to consider. For example, patients may be combining cannabis with other treatment modalities. It’s likely that the quality of the medicine, the cannabinoid profile, and the terpene profile are all contributing factors. And, perhaps very low doses of cannabis can, in fact, contribute significantly to efficacy and treatment success. Clearly, more research is needed.
While Radicle Health occasionally recommends rectal administration for conditions that can benefit from a topical cannabis administration (such as fissures, hemorrhoids, and rectal cancer), this route can produce results that are incomplete, unpredictable, and erratic. Importantly, Radicle Health does not recommend rectal administration for patients undergoing chemotherapy because of the increased risk of infection and rectal bleeding. Patients should always consult with a healthcare professional before considering rectal administration.
Sources
Baviskar, P., Bedse, A., Sadique, S., Kunde, V., & Jaiswal, S. (2013), "Drug delivery on rectal absorption: suppositories.," Journal of Pharmacological Science Review, 21(1). 70-76.
De Boer, A.G., Moolenaar, F., de Leede, L.G., Briemer, D.D. (1982), "Rectal drug administration: clinical pharmacokinetic considerations," Clinical Pharmacokinetics, 7 (4): 286-311.
Elsohly, M.A., Little, T.L., Hikal, A., Stanford, D.F., Walker, L. (1991), "Rectal bioavailability of delta-9-tetrahydrocannabinol from various esters," https://www.ncbi.nlm.nih.gov/pubmed/1664466
Larry A. Walker, Ernest C. Harland, Allyson M. Best, Mahmoud A. ElSohly, “Δ9-THC Hemisuccinate in Suppository Form as an Alternative to Oral and Smoked THC,” Marihuana and Medicine pp 123-135.
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Perlin, E., Smith, O.G., Nichols, A.L., Almirez, R., Flora, K.P., Cradock, J.C., & Peck, C.C. (1985), "Disposition and bioavailability of various formulations of tetrahydrocannabinol in the rhesus monkey," Journal Pharm Science, 74 (2): 171-4.
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