Discovery & Development of Drugs (AQA GCSE Biology: Combined Science)

• Traditionally drugs were extracted from plants and microorganisms
• New drugs are being developed all the time by scientists at universities and drug companies around the world
• Lots of the medications that we use today are based on chemicals extracted from plants
  • The heart drug digitalis originates from foxgloves
  • The painkiller aspirin originates from willow
  • Penicillin was discovered by Alexander Fleming from the Penicillium mould

• Most new drugs are synthesised by chemists in the pharmaceutical industry. However, the starting point may still be a chemical extracted from a plant

Drugs from plants table

• Penicillin was first discovered by Alexander Flemming in 1928. He left some Petri dishes that had been contaminated with mould and found the bacteria would not grow near the mould
• He discovered that the mould (Penicillium notatum) was releasing a chemical (penicillin) that killed the bacteria surrounding it
• New drugs are now developed by the pharmaceutical industry. Many of these still have plants as their source

• All new drugs need to be tested and trialled before they can be used in patients. They are tested for:
  • Toxicity – does it have harmful side effects?
  • Efficacy – does the drug work?
  • Dose – what dose is the lowest that can be used and still have an effect?

• The results of any testing are then peer-reviewed to make sure that the results are described accurately. The results would then be published in journals

• Preclinical testing is done in a laboratory using cells, tissues and live animals
• Clinical trials use healthy volunteers and patients
• Very low doses of the drug are given at the start of the clinical trial
• If the drug is found to be safe, further clinical trials are carried out to find the optimum dose for the drug
• In double-blind trials, some patients are given a placebo

The 3 stages of drug development

• Preclinical Testing
  • The drug is tested on cells in the lab
  • Computer models may also be used to simulate the metabolic pathways that may be taken by the drug
  • Efficacy and toxicity are tested at this stage

• Whole organism testing
  • The drug is tested on animals to see the effect in a whole organism – all new medicines in the UK have to have tests on 2 different animals by law
  • Efficacy, toxicity and dosage are tested at this stage

• Clinical trials
  • The drug is tested on human volunteers first, generally with a very low dose then increased. This is to make sure it is safe in a body that is working normally
  • The next stage is to test on patients with the condition.
    The patients are often split into two groups; one given the drug the other given a placebo. This is called a double-blind study – neither the doctor nor the patient knows if the patient is getting the placebo or the active drug
  • Once the drug is found to be safe then the lowest effective dose is tested at this stage

Future medications

• Pharmaceutical companies are always looking to find new medications these include:
  • Vaccinations to different diseases
  • Antibiotics that have a different action on the bacteria, so that bacteria are not resistant to them
  • Painkillers with fewer side effects
  • Antiviral drugs that don’t damage the body’s tissues

• Sources of these medications may be plants or microorganisms