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

Discovering new drugs

• Traditionally, drugs were extracted from plants and microorganisms

  • Many medications that we use today are based on chemicals extracted using these traditional methods, e.g.:

    • Foxgloves produce digitalis, a drug used to treat heart conditions

    • Willow bark produces aspirin, a painkiller that also reduces fever and inflammation

    • Penicillin was first discovered by Alexander Fleming when he found that bacteria would not grow near Penicillium mould

• New drugs are being developed all the time by scientists at universities and drug companies around the world

  • Most new drugs are synthesised by chemists in the pharmaceutical industry

  • The starting point may still be a chemical extracted from a plant

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 is the optimum dose – the amount that works best with the fewest side effects?

• The results of any testing are then peer-reviewed to make sure that they are scientifically valid, before being published in academic journals

Developing new drugs

• Drug development begins with preclinical testing; during this stage:

  • drugs are tested in a laboratory using cells, tissues and live animals

  • tests check for toxicity and efficacy without risk to human patients

• After a drug passes the preclinical tests, it progresses to clinical trials; this involves:

  1. giving a small group of healthy human volunteers low doses of the drug to check safety and monitor any side effects

  2. carrying out a double-blind trial with disease patients to determine efficacy and find the optimal dosage

     • In a double blind trial half the patients receive the new drug while half receive a placebo

     • neither the patients nor the staff conducting the trial know who has received what; this avoids bias

     • The placebo acts as a control to demonstrate that any results are due to the drug and not any other factor