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 from plants

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

• New drugs are synthesised by chemists, though many begin with plants and microorganisms

Drugs from plants and fungi

• Foxgloves produce digitalis

  • This helps strengthen the heartbeat

• Willow bark produces aspirin (acetylsalicylic acid)

  • This is a painkiller and reduces fever and inflammation

• Penicillin was first discovered by Alexander Fleming in 1928 when he left some Petri dishes contaminated with mould and found the bacteria would not grow near the mould

• He discovered that the mould (Penicillium notatum) was releasing a chemical (penicillin) that killed the bacteria surrounding it

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 dose is the lowest that can be used and still have an effect?

• The results of any testing are then peer-reviewed to make sure that the results are described accurately. The results would then be published in journals

Developing new drugs

• Preclinical testing is done in a laboratory using cells, tissues and live animals

• Clinical trials use healthy volunteers and patients

• Very low doses of the drug are given at the start of the clinical trial

• If the drug is found to be safe, further clinical trials are carried out to find the optimum dose for the drug

• In double-blind trials, some patients are given a placebo

The three stages of drug development

Preclinical testing

• The drug is tested on cells in the lab

• Computer models may also be used to simulate the metabolic pathways that may be taken by the drug

• Efficacy and toxicity are tested at this stage

Whole organism testing

• The drug is tested on animals to see the effect in a whole organism – all new medicines in the UK have to have tests on two different animals by law

  • Efficacy, toxicity and dosage are tested at this stage

Clinical trials

• The drug is tested on human volunteers first, generally with a very low dose then increased. This is to make sure it is safe in a body that is working normally

• The next stage is to test on patients with the condition

• The patients are often split into two groups: one given the drug, the other given a placebo

• This is called a double-blind study: neither the doctor nor the patient knows if the patient is getting the placebo or the active drug

• Once the drug is found to be safe then the lowest effective dose is tested at this stage

Future medications

• Pharmaceutical companies are always looking to find new medications these include:

  • Vaccinations to different diseases

  • Antibiotics that have a different action on the bacteria, so that bacteria are not resistant to them

  • Painkillers with fewer side effects

  • Antiviral drugs that don’t damage the body’s tissues