The History of Pharmacology.
Here is a brief recap of the history of pharmacology. Summarized from my Pharmacology notes. Image source here.
During the age of RELIGION and SUPERSTITION:
People used medicines isolated from plants and animals in order to "rid the body of evil spirits". Note that the route word of pharmacology (pharmakon) is a magical charm used to treat disease.
During the age of TRIAL and ERROR:
Series of trial and error experiments were conducted using plants to treat disease. The first successes were when the plants were used externally to treat disease. In 1500 BC, there are reports of castor oil being used externally to treat ailments. It was until 2100 BC that the first prescriptions were written. Most of the pharmacists were monks who spent their time studying herbal medicines.
During the age of SCIENCE:
Rationalization became important. The scientific method was used. Pure drug compounds were finally isolated from natural sources.