Topic Summaries

Modern and historical drug development

GCSE > Biology > WJEC > GCSE Biology Topic Summaries > The immune system and drugs > Modern and historical drug development
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Plant disease and monoclonal antibodies

The brain and the eye

Reproductive hormones and plant hormones

Genetic engineering and modification

Resource cycles and environmental change

Science skills: Measuring results

  • Drugs were traditionally extracted from plants and microorganisms. For example, the painkiller aspirin comes from the willow tree, and the heart drug digitalis comes from foxgloves.
  • Penicillin was discovered accidentally by Alexander Fleming from the Penicillium mould, which contaminated his petri dish of bacteria.
  • Most modern drugs are artificially synthesised by chemists in the pharmaceutical industry (e.g. paracetamol).
  • It is difficult to develop drugs that destroy viruses without also damaging the body’s tissues, as viruses are active within human body cells.
  • The key stages in modern drug development are:
    • Identifying a potential drug: this may be a chemical extracted from another organism like a plant, or a new artificially synthesised chemical combination.
    • Computer modelling: investigate the drug's structure and potential interactions with substances in the body.
    • Preclinical testing: checks the drugs are safe and effective (e.g. testing for toxicity and efficiency) in a laboratory using live cells, tissues, and animals.
    • Clinical trials:
      • First phase uses healthy volunteers to test toxicity.
      • Very low doses of the drug are given at the start of the trial. If the drug is safe, it will be given to a small number of sick patients in phase two to test efficacy.
      • Phase three trials use more patients and finalise safe, optimum doses.
      • In double-blind trials, some patients are given a placebo to test whether the drug is causing the improvement in patients or if it is just the placebo effect.
    • Manufacturing: producing the drug on a mass scale to make it publicly available.

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