Using plants as medicines is thought to date back to prehistoric times and the oldest medical text known is from about 1800BC. However it was only at the start of the 1900s that medicines really started to expand and become truely beneficial. It was only in 1962 that the Government required all new drugs to be tested for efficacy and safety in clinical trials. Sorry, I know this doesn’t properly answer your question but I don’t know the exact answer
Comments