Route of administration
By Alex MacNeil | Budtender
THC and Its Journey To The Brain
A rose by any other name may be just as sweet, but a big breath of vapor certainly has its special features over some tincture under your tongue. A dab can’t be compared to a brownie, or can it? Let’s dive into the fine tune factors of different routes of administration, or as we’ll address it, different ROAs! For each ROA we’ll consider a few points regarding pharmacokinetics! Think of that as the speed of uptake of THC, the path and distribution as it travels to the brain, and the duration it hangs around. These aren’t the strict talking points for pharmacokinetics but it’ll do for our purposes. Secondly, efficiency! This will tie into the pharmacokinetics, but always has a few fine tune features. Finally, some ROAs have special notes to save for the end.
Inhalation is a very common form of intake. What’s more elegant than breathing? This route offers very fast uptake. The smoke or vapor travels through the mouth, down the trachea, into the bronchioles, and finally into the deep depths of the lung. Rapid diffusion picks up nearly all the THC and dumps it into the bloodstream. At this point it’s a fast track to the brain. From the lungs, to the heart, and straight to the brain! Bam! Allegedly seven seconds later your receptors are being tickled. This ROA has little THC dropped on the way to the brain, but is also cleared out faster than any other form. Consider the shorter high you may have experienced. Efficiency will vary depending on the user’s style and the form used. Only part of the THC will be metabolized to 11-OH-THC. We’ll address the difference between THC and 11-OH-THC in a future article. For now just remember the latter is a bit stronger than the former.
For those looking for a slightly slower uptake, sublingual may be their preference. This route offers a quick transfer from mouth to bloodstream. While the vessels in the mouth are rather close to the brain, it’s a longer path to the brain vs inhaled. From the mouth, to the face, to the jugular, and into general circulation. Now to the heart heart, to the lungs, to the brain! When using sublingually the THC also hangs around longer than smoking, but the high usually subsides in one to four hours. This path is rather efficient! There’s little THC reaching the liver early on, making for limited conversion to 11-OH-THC.
Things start to get complicated with oral administration. Tasty, but full of little variables. Quick to the stomach, but everyone digests a little differently. Some may clear their stomach quickly, others might hold the THC there for a while. That stomach acid isn’t friendly to THC! Once the THC gets to the small intestine the uptake will vary from person to person too. From the bloodstream there’ll be circulation around the body a bit, but most directed to the liver. From the liver, around the body, to the heart, to the lungs, to the heart again, and now to the brain! With its slower uptake it also hangs around the body the longest. This path has a lot of opportunities for THC to be left behind as it travels to the brain. Considering not all of it gets through the stomach you’d think this ROA isn’t very efficient either… but there’s a trade off. Full conversion to 11-OH-THC! Also consider the blood sugar boost to fight hypoglycemia, or low blood sugar, which THC can cause.
Likely the least common form of dosing is suppositories. This ROA offers an uptake roughly the same speed as ingestion and the longest path to the brain. The circulatory system has two branches, one for the upper body and one for the lower. This path keeps all the THC in the lower until reaching the heart. You should have an idea what comes next: From the heart to the lungs, to the heart, to the brain! The liver and stomach are avoided, so once the THC is absorbed there’s little destruction Consider the limited psychoactivity from this ROA. This indicates very little reaches the brain. Lots of chances for THC to be deposited in the body and not make it to our goal. The duration is similar to orally ingesting THC. The efficiency will be similar or up to twice to the oral ROA. Not as much will reach the brain, but less will experience first-pass metabolization.
Another uncommon, but up-and-coming ROA, is transdermal. This technology is more often used in medical settings when someone needs a prolonged and constant supply of a drug. The product will diffuse through the skin, often with transport agents to allow the THC to reach the bloodstream. Mechanical advantages can be used too, such as tiny teeth to rough up the skin. This ROA is very efficient, slow, and long acting. The pharmacokinetics will vary depending on what part of the body is used. Often the bottom of the forearm is preferred for the blood vessels which are close to the skin. Consider, if the leg is used the THC has a much longer to reach the brain. This example will give very little psychoactivity, but rumor has it the vessels on the neck go straight to the brain!
Topicals are very much like transdermal, but lack the extra transport agents or mechanical advantages. Little to no THC will diffuse to the bloodstream. This fast but short acting route acts where applied only. Quickly, but for a short amount of time.
Now the next time you serve a dab you can explain why it’s going to hit so fast. Your next cannabutter batch will predictably creep up. And hey, if you’re living in the future you’ll know why you’re stoned for so long from a transdermal patch! When introducing someone to cannabis they’ll be more comfortable if you can explain why different forms act differently. Then blast their mind with the word pharmacokinetics!
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McGilveray, Iain J. “Pharmacokinetics of cannabinoids.” Pain Research and Management 10.Suppl A (2005): 15A-22A.
Grotenhermen, Franjo. “Pharmacokinetics and pharmacodynamics of cannabinoids.” Clinical pharmacokinetics 42.4 (2003): 327-360.