For many years we have know about drugs that come from natural sources, for example willow bark was used by the ancient Greeks to help cure fevers and pains. Later on in time people discovered that the active ingredients was salicylic acid. This was later modified into aspirin which is less irritating to the stomach than salicylic acid.

Today drugs have to be tested before they can be prescribed to the general public for medical uses. First they will do lab test on human cells in the lab. This stage is first as they will not damage the living human as the cells are not in their bodies and there is only a limited amount of cells they can damage. Many drugs fail at this first part as they damage the human cells or have no effect on the pathogen. If they pass the lab tests they will then be tested on animals. This is very controversial as many people don’t like this stage as it may harm the animal. The infected cells and the drug will be monitored for any side effects and the effectiveness. There will be side effects on many drugs and defends on what the side effects are, if the side effects are worse that the disease that they are trying to cure they will have to be redeveloped. If the side effects are not worse than the disease they move to stage 3. They then go to clinical trails, they are tested on healthy humans who volunteered to be tested on. This is to see if the drug causes any harm. It will then be tested on people with the infection to make sure it curse the diseases and does not cure harm to the human.