Character A needs to render Character B unconscious without causing long term damage.
Character B is an adult male in generally good health but a bit run down. He’s not going to be cooperative.
Character A only has access to what he can carry with him (so no bulky equipment) but could have illegal or unusual technology. There is no access to medical equipment, so the method used can’t paralyse Character B so that he needs mechanical ventilation.
My problem is most of the common literary methods of knocking someone out seem to be either dangerous or ineffective.
What I’ve searched: Google searches and LD tags around the following:
A blow to the head: high risk of long term brain damage.
Tranquiliser darts: ineffective unless the dose is carefully managed and risk of overdose.
Taser: doesn’t actually render unconscious.
Ether/ chloroform on a rag: doesn’t seem that effective? – can’t see how Character A won’t end up getting a dose himself.
Intravenous injection: seems most likely but not sure how it would work with an uncooperative, unrestrained Character A?
Thanks for all help.