how was ketchup used as medicine?

Answer 1

As an alternative medicine, Ketchup could be used for the benefits it provides from Vitamin C. So, for colds, Ketchup might be a preventive medicine. Also, there is enough sugar in Ketchup to use it (in an emergency situation only, and only when no purer forms of sugar can be found immediately) on a diabetic that is in need of immediate insulin.
You qualified your Q with the word "WAS" and that is important. Today we have better ways of getting Vitamin C and we have a 911 system for emergencies.
Interesting Q. Good Luck !

Answer 2

It was mixed with crack and eaten