3.1.9 Discovery and development of drugs

• Drug: Digitalis

  What is it?: A heart drug

  Extracted from: Foxgloves
• Drug: Aspirin

  What is it?: A painkiller

  Extracted from: Willow trees
• Drug: Penicillin

  What is it?: An antibiotic

  Extracted from: Penicillium mould
• discovery of penicillin by Alexander Fleming:

  ● Noticed bacteria in Petri dish killed by mould

  ● Realised mould released chemical that killed bacteria
• How are most new drugs synthesised?

  ● Synthesised by chemists in the pharmaceutical industry

  ● Starting point may still be a chemical extracted from a plant
• What 3 things are new drugs extensively tested for?

  ● Toxicity (side effects / how poisonous / safe)

  ● Efficacy (if it works)

  ● Dose (most suitable conc. to be used)
• How are new drugs tested before use?

  Preclinical testing

  In a laboratory using cells, tissues & live animals → aim: to test for toxicity / to see if safe / if it works
• 2. Clinical trials

  ● Phase 1: Drug tested on healthy volunteers using very low doses ○ Aim: to test if it is safe / check for side effects / toxicity

  ● Phase 2 & 3: Drug tested on patients with disease (small then larger number)

  ○ Aims: to test for efficacy (if it works), side effects and optimum dose ○ Normally double-blind:

  ■ Patients randomly split into 2 groups

  ■ 1 group given placebo (tablet that does not contain the active drug), other given drug

  ■ Neither doctor or patient know who is given drug vs. placebo
• Why is this statement wrong?

  A placebo is a drug that doesn’t work or affect the body.”

  A placebo looks exactly like the drug but doesn’t contain the drug. Unlike drugs, it doesn’t affect body chemistry
• In phase 1 of clinical trials, suggest why healthy volunteers are used. (1)

  ● Too great a risk for a patient

  ● Side effects easier to identify
• In phase 1 of clinical trials, suggest why very low doses are used. (1)

  ● To reduce risk (if unsafe, less harm caused)

  ● To look for harmful side effects / toxicity
• Suggest why double-blind trials are used. (1)

  ● To avoid bias (eg. doctors analysing results being influenced by knowledge of the drug)
• Suggest why [in named context eg. testing for cancer drugs] a placebo is not used. (1)

  ● Unethical not to treat ill patients / may become more ill if no drug
• Suggest an alternative to a placebo. (1)

  ● Standard treatment for disease
• Suggest why results are published only after scrutiny by peer review by other scientists. (2)

  ● To ensure results / conclusions are valid

  ● To prevent false claims

  ● To avoid bias
• Why is this statement wrong?

  "Healthy patients are used for phase 1 of clinical trials.”

  Healthy volunteers are used for phase 1 of clinical trials. A patient is a person who is receiving medical care, ie. they are ill.
• Suggest why a placebo is used. (1)

  ● To take into account a psychological effect

  ● So acts as a control / allows for comparison with drug