That A-Z of Tropical Fish Diseases and Health Problems alluded to in a response to your diary is pretty good that way. You have to cross-reference some entries.

Maggie raised a version of your question several months ago. I prattled away with what little I know or could find.

Human Antibiotics for Fish Consumption    
Health and Medicine
By maggie1270
from the Maggie1270 department, Section Ask Guppylog
Posted on Tue Feb 3rd, 2004 at 17:10:15 PST

Virtually every fish remedy was previously developed for people and then the livestock industry. There's no profit in developing meds specifically for ornamental fishes.

These veggie extracts by Aquarium Pharmaceuticals come close to being specifically developed for fish. But they are investigating products which are already being used for people in a number of applications.

Several of the items in your list are in the "family" of Penicillin. As organisms (through over use, just using it as a preventative treatment) made that first medication less than useful, Tetracycline was developed. As is became less useful Ampicillin was developed. We (as humans) have a poor track record of over medicating and medicating for the wrong disease and helping to create a world of medicine resistant microbes.

Years ago, I even secured quinine, as per a very old aquarium book, for a fish remedy. The pharmacist was so intrigued by the situation, he just gave me a small package of the stuff along with a "good luck".

As you have found some popular remedies were too popular and no longer are effective. Triple Sulfa may still work for mouth fungus (the more benign columnaris). Go figure.