AQA GCSE Biology

Revision Notes

3.1.9 Discovery & Development of Drugs

Discovering New Drugs

  • 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

Drugs from plants table, downloadable IGCSE & GCSE Biology revision notes

  • 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

Testing New Drugs

  • 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

Developing New Drugs

  • 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

Exam Tip

You should be able to describe the process of discovery and development of potential new medicines, including preclinical and clinical testing in the exam.

Author: Jenna

Jenna studied at Cardiff University before training to become a science teacher at the University of Bath specialising in Biology (although she loves teaching all three sciences at GCSE level!). Teaching is her passion, and with 10 years experience teaching across a wide range of specifications – from GCSE and A Level Biology in the UK to IGCSE and IB Biology internationally – she knows what is required to pass those Biology exams.

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