Edexcel International A Level Biology

Revision Notes

4.13 Development of Drugs & Drug Testing

Test Yourself

Development of Drugs & Drug Testing

  • Whenever new drugs are developed, they first need to be tested for effectiveness and side-effects, before they can be sold to the general public
  • These are known as clinical trials and are crucial to avoid exposing the public to drugs that may pose a risk to their health
  • Drug testing has not always been this scientific or regulated in the past

Digitalis soup

  • William Withering was an English scientist from the 1700s
  • He is best known for his work on using digitalis as a treatment for swelling caused by heart failure (known as dropsy)
  • Withering treated his patients with an extract made from foxgloves, which contains the drug digitalis
  • Foxglove is poisonous to humans, so he made different versions of his remedy containing different concentrations of digitalis
  • These versions were called his digitalis soup
  • He experimented on his patients to find the most effective concentration of digitalis that would treat dropsy without poisoning the patient

Modern methods of drug testing

  • Modern drug testing protocols are much more rigorous than those of the past
  • The first step is modelling the potential effects of the drug, using computers
  • Next, the drug will be tested on human tissues in a laboratory, before being tested on animals
  • Should the drug pass these steps without causing any major problems, then it will continue to the clinical trial stage where human test subjects will take it
  • There are three phases of testing during clinical trials:
    • Phase 1 involves a small group of healthy individuals to determine how the body will react to the drug, the side effects of the drug and the correct dosage that should be taken
    • Phase 2 will be done on a larger group of patients (non-healthy individuals who require the drug) to determine the effectiveness of the drug
    • Phase 3 involves comparing the drug to existing drugs to see if it works any better. A large number of patients are split into two groups, each of which receives either the new drug or the existing one


  • Placebos are typically done during phase 2 of a clinical trial
  • Patients are split into two groups - one will receive the drug and the other group will be given a placebo, which looks exactly like the drug but contains no active ingredients
    • The patients are not told which group they are in
  • This provides a way for scientists to determine whether the drug actually works
  • Certain patients display what is known as the placebo effect 
    • This is where a patient will show improvements in their health due to the belief that they are receiving the drug

Double blind studies

  • These happen during phase 2 and 3 of clinical trials
  • Double blind means that neither the patient nor the doctor knows which patient is receiving the drug or the placebo
  • This reduces the effect that the attitude of either doctor or patient may have on the results
    • For example, in some cases, a doctor may believe a patient is improving more if they know the patient is receiving the drug

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Author: Marlene

Marlene graduated from Stellenbosch University, South Africa, in 2002 with a degree in Biodiversity and Ecology. After completing a PGCE (Postgraduate certificate in education) in 2003 she taught high school Biology for over 10 years at various schools across South Africa before returning to Stellenbosch University in 2014 to obtain an Honours degree in Biological Sciences. With over 16 years of teaching experience, of which the past 3 years were spent teaching IGCSE and A level Biology, Marlene is passionate about Biology and making it more approachable to her students.