Edexcel A (SNAB) A Level Biology:复习笔记4.2.8 Development of Drug Testing

Development of 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 on 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, 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