Communicable Diseases (OCR GCSE Biology A (Gateway Science Suite)): Revision Notes
📚 Revision Notes
3.1.9 Discovery & Development of Drugs
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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.
Plants
The chemicals that plants use to kill pests and pathogens can be used to treat symptoms or human diseases.
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EXAMPLES:
- Aspirin is used as a painkiller (originates from willow)
- Digitalis is used to treat heart problems (originates from foxgloves)
Microorganisms
- Penicillin
- Alexander Fleming was growing bacteria on plates
- He found mould ( Penicillium mould ) on his culture plates, with clear rings around the mould indicating there was no longer any bacteria there
- He found that the mould was producing a substance called penicillin, which killed bacteria
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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).
The results then need to be peer reviewed by other scientists to check for repeatability.