RECTAL ABSORPTION OF CANNABIS – REVISITED

I have written several blogs on Rectal Administration of Cannabis. Since the writing of that blog, there are several issues that have come to light.

1. I think many know that when THC is administered via the rectal route, it does not cause any psychoactivity or stoniness. Why?
We will discuss. If we are talking about treating cancer, it becomes critical to know if the lack of psychoactivity is due to some unknown cause or just because it is not being absorbed. There is venous drainage from the rectum.

However, that does not necessarily mean that it is being absorbed into the blood. After studying the venous drainage of the rectum, it SEEMED that cannabinoids should/would go through both portal or liver circulation as well as systemic venous circulation. Well, read on….this may not be happening?

2. We have performed some very initial plasma THC and CBD levels following rectal administration of cannabis oil in cocoa butter. The levels were extremely low; barely detectable. This needs to be repeated on many patients, but it does not sound crazy to have very low plasma levels correlating with no psychoactivity. So, nothing is felt by the patient and early studies show low plasma levels
following rectal administration. What could explain this?

3. Perhaps the answer is the following. Searches looking for fat or oil absorption from the rectum** show around 3%, at the most, of any oil is rectally absorbed. As Cannabis is nearly entirely fat or oil based – AND oil is very poorly absorbed rectally, perhaps whole plant cannabis oils are in fact poorly absorbed rectally?

4. There is an often quoted article using molecular THC in hemi-succinate. The reference is below. We can’t use this article’s conclusions for any oil based cannabis product and this is the only type of cannabis products we work with as we don’t work with molecular cannabinoids. Whole plant cannabis extractions are a thick oil and just may not be absorbed because of the oil.

The lack of psychoactivity does not make sense, early blood level testing shows minimal absorption and we know that fats/oils are not absorbed rectally. In addition, there is no data in the literature showing that oils are well absorbed rectally. Attempts to feed patients rectally failed. Clearly more plasma studies are indicated.

In spite of some of the medical findings above, I do have several patients with positive results from using rectal administration of cannabis, so further research will certainly be beneficial.

**Reference on rectal oil absorption
https://books.google.com/books?id=Tkd6ngkksqcC&pg=PA737&lpg=PA737&dq=absorption+of+fat+rectally&source=bl&ots=lc0dUmOKPd&sig=EI0EhazQ5Xr78joWnSj5Sk8_Op4&hl=en&sa=X&ved=0ahUKEwiszbKdlrnKAhVJ6WMKHaXjA-MQ6AEIMTAG#v=onepage&q=absorption%20of%20fat%20rectally&f=false

** Reference on hemi-succinate
http://www.ncbi.nlm.nih.gov/pubmed/1664466

Author
Allan Frankel, MD

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