Ex-drug user here! So, I was always told that snorting the drug is always a better, faster, way to get high (compared to orally using the drug). What’s going on biologically here? Also, why don’t they prescribe medicines nasally if the drug absorbs into your system better or faster?
In: Biology
This is actually a really interesting question. I work on transdermal drug delivery. So you essentially have two questions here. First, why is the drug uptake higher in the nose? So the idea is that while the inside of your nose might appear to be just skin, it’s actually a specific type of skin called “mucosa”. In many regions, such as the tympanic membrane (or ear drum), this mucosal layer is covered by a thick, less porous/permeable layer of skin. While it’s all “skin”, the chemical makeup is different. Specifically, the skin in your nose is very permeable to small molecules like drugs AND the nose is highly vascularized, which basically means you have a lot of blood vessels. This makes sense if you’ve ever had a nosebleed right? You may get the tiniest scratch, so small it doesn’t even hurt, but it can cause profuse bleeding. The combination of these two traits allows medicines and bioactive molecules to enter your bloodstream much quicker!
Now, for the second question, the answer is a bit more complex. Sometimes, they do prescribe drugs for nasal use! One of the main issues with this though is that often times we care about where the drug goes, and how quickly it goes there. Sometimes, we don’t want the drug to get absorbed really fast. Say you’re trying to deliver antibiotics or an extended release dose, in that case, the fast uptake hinders the ability of the drug, since you ideally want to maintain a certain amount entering and being taken up by the body over a period of time. Additionally, because of the difference in biology, the nasal passage can be especially prone to irritation. If you’ve ever taken the nasal allergy sprays, you might know that one of the common side effects of these is recurrent nose bleeds. So not all therapies work in the nose, because there are different levels of side effects people are willing to have and there are different rates we want drugs to be taken in by the body. Hope this helps! Happy to answer any follow-up questions as well.
Edit: additionally, though this may be too in-depth for ELI5, there are barriers to drug transport within the body. An example of this is the Blood-brain-barrier. I won’t go in-depth on it, but basically these barriers can also make it harder for you to metabolize certain chemicals
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