Many drugs were initially discovered in plants and microorganisms. New drugs today are mainly synthesised by chemists. They need to be tested for toxicity, efficacy (how well they carry out their role) and dose, using preclinical testing and clinical trials.

Any new drugs being developed need to be tested to ensure they are safe and effective. Preclinical testing : using cells, tissues and live animals

Clinical testing : using volunteers and patients

• It is first tested on healthy volunteers with a low dose to ensure there are no harmful side effects
• The drugs are then tested on patients to find the most effective dose
• To test how well it works, patients are split into two groups with one group receiving the drug and one receiving a placebo (appears to look like the drug but has no active ingredient so no effect) so the effect of the new drug can be observed
• These can be single-blind (only the doctor knows whether the patient is receiving the drug) or double blind (neither the patient or doctor knows whether they are receiving the drug, removing any biases the doctor may have when they are recording the results).