There are numerous, very contradictory reports on the rectal application of cannabis online that range from “absolutely ineffective” to “best ever.” The research on this type of medicine intake is almost non-predictive because there are only two relatively small studies from 1985 and 1991. Both studies conclude that the bioavailability of THC taken rectally is very poor compared to eating or inhaling.
On the other hand, there are many positive and credible testimonials from patients and consumers, most of them reporting a muscle-relaxing and pain-relieving effect. Further to that, people report a long lasting high after having applied cannabis rectally. Individuals report that the psychoactive effect is not as distinctive as smoking or eating, but that it does last longer.
How much THC actually gets into the blood when smoking or eating?
The bioavailability of inhaled or ingested cannabis is not as significant as one may expect. Depending on the depth of inhalation, the duration of the puff, and the length of time the inhalant stayed in the lung, only 10 to 35 percent of the available THC in a joint will reach the smoker’s bloodstream; 65 to 90 percent of lost THC is a result of side streams and incomplete uptake of THC via the mucosa of the respiratory tract; 30 percent is lost through combustion before inhalation. Vaporizing cannabis, however, is more effective. In a vaporizer test that did not include blood testing, it was found that an average of only about 35 percent of the available THC was exhaled by the subjects.
For oral intake (food and/or drink) the maximum THC blood concentration is determined after 60 to 120 minutes. Some of the THC is digested by gastric acid, but most of it is absorbed in the upper gastric region and reaches the liver via the portal vein. At this stage, most of the THC is metabolized; only 4 to 12 percent of the ingested THC gets into the consumer’s blood circulation. However, some metabolites of THC, especially the metabolic product 11-hydroxy-THC (11-OH-THC), act similarly psychoactive to THC after passing through the liver.
The Efficiency of Cannabis Suppositories
In the studies to which all medical claims have been based so far, it has been found that the bioavailability of rectally applied THC is significantly increased if the THC molecule is transesterified beforehand. The THC-Ester THC-hemisuccinate (THC-HS) is absorbed better in the rectum, it then passes directly into the bloodstream to reach the liver where it is finally metabolized. The first patent for such THC suppositories was filed in 1994. In relevant forums, you will also find detailed instructions how to transesterify THC into THC-HS. In addition, the medical experts in the mid-90s found that plant fats such as coconut fat are poorly suited as THC carriers. Any active substances in a suppository must first dissolve in the aqueous mucus of the rectum before entering the bloodstream. Without the transition through the aqueous mucus layer, the THC can not be absorbed directly. Greasy or oily carriers like the cocnut fat mentioned above reduce absorption, active substances such as cannabinoids should not be combined with them for the preparation of suppositories. The best bioavailability was achieved when THC was linked to THC-hemisuccinate and a pharmaceutical glycerol (Witespot 15, a substance often used in suppositories, as carrier material). The bioavailability strongly differed depending on suppository formulations. Comparing THC-HS to other polar esters of THC, Witepsol H15 mixed with THC-HS showed the highest bioavailability when evaluated in monkeys. The carrier substance is offered as an “emulsifying wax” for suppository-production by pharmaceutical wholesalers and has similar properties as the less effective greasy or oily carriers. With the transesterified active substance, an average THC content of 13.5 percent was found in the monkeys under evaluation. The rectal bioavailability of this formulation was calculated to be about as twice as high as oral bioavailability of THC.
The bioavailability in another small, hardly exhaustive study by the Swiss pharmacist Professor Rudolf Brenneisen evaluating the effects of oral (Marinol) or rectal THC-HS on two patients back in 1996 was found to be roughly 50 percent. Brenneisen concluded that rectally administered THC-HS has higher absorption and lower first-pass metabolism than if administered orally.
The German Cannabinoid specialist Dr.Franjo Grotenhermen writes: “I have also learned of self-tests by cannabis users, who have taken natural cannabis preparations rectally. For example, ground dry marijuana was cooked in cocoa butter for an hour. After cooling, suppositories were formed. The typical cannabis effect was felt within about ten minutes. However, there are no reliable data on these self-tests.”
Of course, as a long-standing cannabis patient with a recommended daily dose of 650 mg THC, I tested the aforementioned application form. In order to avoid a lipophilic carrier, I used about one and a half grams of freshly sieved hashish powder on a trip to the Rif Mountains in Morocco. I kneaded it into the right shape, and did what I had to do for my experiment. The hash had a THC content of about 35 percent, which I had measured with test strips I carried from the Netherlands. The piece of hash thus corresponded to a dose of about 500 mg of THC. It became effective roughly 60 minutes after ingestion. Its effect was relaxing and anticonvulsant; the high was clear, not too psychoactive, and not as strong as eating the same amount of THC. The effects lasted nearly eight hours.
Almost all statements on the bioavailability of rectally applied THC cite a 27-year-old study on a few monkeys. The monkeys could not report on the experience, and only the THC-content in the bloodstream was measured. Those studies were conducted before cannabinoid receptors or the existence of a cannabinoid system was discovered. Since then, scientists have discovered that the effect of cannabis is a combination of many components working synergistically; scientists call this the entourage effect. It is doubtlessly proven that THC-HS increases the bioavailability of THC when it comes to rectal intake. However, there are a lot of user experience reports, many of which confirm the pain-relieving and exhilarating properties using a lot different methods and carrier substances to prepare suppositories. Apart from this, reports about a pleasant and unambiguous high are never done without THC-HS but with cannabis, hash or extracts. For many cannabis patients with gastric and intestinal problems, the rectal intake would be the ideal application form. In order to better decipher this potential and the mechanisms involved, more studies are urgently required to explore this issue under the scientific method.
Photo credit: Lukasz Siekierski