From past reading in various sources there seems to me to be many ways to administer molecules into the human body without injections that cause tissue trauma but that these ways generally aren't effective for the direct administration of certain materials (described below).
non-injectable administration ways I know are these:
Gastric and intestinal
- Sackets (common as Snus)
- Chewed leaf caches in one side of the mouth (common with Khat leaf consumption in some cultures)
Reception is primarily in upper respiratory tract:
- Nose sprays
- Nose (sniffing) inhalers
- Nose (sniffing) drops
- Ear drops
- Eye drops
- Solutions (including drops)
- Powders (such as Talc)
Reception is primarily in lower respiratory tract:
- Inhaling (via nasal and/or oral route)
- Smoking (primarily via oral route)
- Changes to body modes could be also achieved by radiation and other physical ("non chemical") and thus
I am not sure I understand what is the main problem with using these ways for a small company of materials → mainly:
- Peptide hormones (which aren't proteins)
- proteins (including peptide hormones which are indeed proteins)
I understand that these two usually (but not necessarily always) break into amino acids in the stomach or are too big to cross via non gastric tissues, hence, either a human get too little of them, or not at all.
There might be more problems I am not aware of.
What are the main problems with non-injectable ways to administer molecules into the human body?