I don't know how they make them, but I know what I would do as an experiment.
As I see it, this breaks down to:
- The base of the medicine is most likely some type of concentrate, probably oil or alcohol based. I make QWISO, so I would use that as my basis, but an oil extraction should also work.
- If you are interested in CBD or other fractions of the active elements, you may need to do some research on separating out the fractions you want.
- THC has to be activated to be psychoactive, which requires heat.
- The concentrate needs to be able to be absorbed into the skin, which won't happen without something to facilitate absorption. I keep DMSO on hand, so I would use that. DMSO is easy to get, most feed stores & ranch stores sell it (including Tractor Suppply C0). DMSO facilitates absorption through cell walls for both plants & animals - I use it for helping to pop really old seeds and for treatments for my livestock.
- For the patch itself, I would buy some bandages that seal to the skin on all 4 sides. Remove part of the gauze pad to reduce the amount of concentrate needed to saturate it (waste not, want not)
I would dissolve the QWISO in a bit of alcohol and heat it to activate it. Be VERY careful if you do this on a stove - alcohol will catch fire! I would then cool the activated oil down, mix in a drop or two of DMSO, and then put the resulting goo on the gauze or cotton section of the bandage. Seal it away from air and keep in the fridge until needed. Don't make many at once, once the THC is activated, it doesn't last a real long time.
Your popping old seeds in DMSO ? and works ? tell me more please.....
Disclaimer - I am not a chemist so I could be way off on this. I am not recommending that you do this without doing some research on your own first. What I posted here is not a real set of directions - for example, you need to look up what temperature will activate the THC and if it requires a certain amount of time.