New drugs are being developed all the time. Historically drugs have come from nature, as parts of plants and microorganisms have been extracted. One of the most famous discoveries was made by Sir Alexander Fleming, who discovered the antibiotic penicillin from the penicillium mould. By chance, he discovered that where an agar plate of bacteria had been contaminated by a mould, the bacteria had been killed.
Antibiotics are still very important in the fight against disease.
Certain drugs can be extracted from natural sources, and have been known about for a long time. For example, willow bark was used by the ancient Greeks to help cure fevers and pains. It was later discovered that the active ingredient was salicylic acid. This was modified by chemists into the substance we call aspirin, which is less irritating to the stomach than salicylic acid. Another example is the heart drug, digitalis which is extracted from foxgloves.
Plants are still important today, but most drugs are now created in a laboratory by scientists at pharmaceutical companies. These companies now have synthetic versions of the plant extracts, and use these as the starting point to develop new drugs.