If nothing else is available mold penicillin and mosses make acceptable wound treatments. I know they’re not regulated and low or of unknown potency.
But if it is a question of nothing and dying from gangrene I’d give some thought to sphagnum peat.
I’ve had universal success with recluse spider bites and seriously nasty puss filled infections with carbolic acid salve.
No shelf life on any of those products.
Sorry about the graphic wound description, just wanted to illustrate what is possible beyond traditional pharmaceuticals.
Clean water will take you farther than most anything.
Capsaicin or pepper derivatives were used for the treatment of giardia or intestinal parasites. Also little to no medical literature available on this, no profit motive.
It wont work on everything but if it’s a choice of 72 hours of cramps and dysentery. Might try a tablespoon of capsaicin powder.
Other intestinal treatments for things like cholera were clean water hydration frequently with a salt and sugar solution.
Chewing tobacco will work on some types of plant secretions irritants.
If you’ve ever been in stinging nettle chewing tobacco stops the burn of stinging nettle almost immediately. Jewel weed is effective treatment for poison ivy.
Bottom line for me would be good supply of bar soap, water purification ability and how to make Dakin’s solution, 4 cups boiled water 1/2 teaspoon of baking soda, and 11/2 tablespoons of plain 5% bleach. Good for everything from serious skin irritation to deep wound irrigation.
I know I dumped a lot and most of it is all non-traditional folk treatments.
Knowledge is power and when modern medicine is gone you have everything to gain by trying what was done for 1000’s of years. Well it’s a no brainer for me.
If your really desperate and adventurous and intravenous hydration and feeding is not available you could always try rectal hydration and feeding. I’ve no experience on this

and only read about it cursorily.
But again if it’s a choice between watching someone die from dehydration or something that might possibly work when nothing will stay down. Stuff your queasy stomach and distaste in a box and close the lid.
I think bleeding patients has universally been proven ineffective. Any benefits from this procedure probably were derived from the short term neuralepinephrine release into the system in response to blood loss.
Ill stick to a cold showers for this treatment