Testing Medicines

• Medicines extracted from plants

  • Foxglove plant used to extract the heart drug digitalis
• Medicines extracted from plants

  • Willow trees used to extract the painkiller aspirin
• Medicines extracted from microorganisms

  • Penicillium mould used to discover penicillin
• Most new drugs are synthesised by chemists working for pharmaceutical companies
• The starting point for new drugs is still often a chemical extracted from a plant
• Drug testing

  1. Check toxicity (safety for humans)

  2. Check effectiveness (treats the disease)

  3. Work out best dose
• Preclinical testing

  Testing not carried out on humans because the drug could be extremely toxic
• Preclinical testing

  Carried out on cells, tissues and live animals
• Clinical testing

  Testing carried out on humans
• First stage of clinical testing

  Give very low doses to healthy volunteers to check drug is safe for humans
• Further clinical testing

  Find the optimal dose to treat the disease with the fewest side-effects
• Placebo

  A tablet or injection with no active drug in it
• Some patients will get better if you give them a placebo
• Patients think they're being treated so they believe they're going to get better
• Double blind test


  Test group receive the active drug, placebo (control) group receive a dummy drug
• In a double-blind trial, neither the patients nor the doctors know which people are receiving the active drug and which are receiving the placebo
• This is to stop bias in case the doctors pay closer attention to people receiving the active drug