Discovery and Development of Drugs
Laura Armstrong & Joe Wolfensohn
Teachers
Contents
Recall Questions
This topic requires prior knowledge of how pathogens cause disease and how the immune system responds.
What is a pathogen?
A microorganism that causes disease, such as bacteria or viruses
How do white blood cells help defend the body?
They engulf pathogens, produce antibodies, and produce antitoxins
Why don’t antibiotics kill viruses?
Because viruses live and reproduce inside cells. Antibiotics can’t target them without damaging body cells
Topic Explainer Video
Check out these @JoeDoesBiology videos that explain the discovery and development of drugs, then read the study notes. Once you’ve gone through them, don’t forget to try the practice questions!
Discovery and Development of Drugs
Traditional Drug Sources
- Many modern medicines were first discovered in plants or microorganisms.
- Digitalis (for heart problems) → from foxgloves.
- Aspirin (painkiller) → from willow bark.
- Penicillin (antibiotic) → discovered by Alexander Fleming from the Penicillium mould.
Drug Discovery & Development Process
New drugs and medications are tested for 3 things before they can be approved and sold or prescribed.
They are tested for toxicity (whether the drug is safe or causes side effects), efficacy (does the drug actually work?) and dosage (how much of the drug is needed).
Drugs are tested in 2 stages, preclinical and clinical.
|
Stage |
Description |
Purpose |
Further detail |
|
1. Preclinical Testing |
Laboratory tests on cells, tissues, and live animals. |
Mainly to test for toxicity and side effects. |
|
|
2. Clinical Trials Phase 1 |
Very low doses tested on a small number of healthy volunteers. |
Mainly to test for side effects. |
Healthy volunteers are needed so that anyone that is sick is not made worse and so any side effects can be seen. |
| 3. Clinical Trials Phase 2 |
Trials on a small number of patients with the disease. |
Mainly to test for efficacy (to check the drug actually works) and monitor short-term side effects. |
A very small dose is used to reduce the risk and any potential side effects. |
|
4. Clinical Trials Phase 3 |
Trials on large groups of patients, often across multiple locations. |
To determine the optimum dose and detect rare side effects. They can also check that the drug does not interact negatively with any other medication. |
Gradually an increased dose is used to find the minimum dose that has the desired effect. |
During clinical trials double-blind trials are used.
- Some patients get the real drug, others get a placebo.
- Double-blind means neither the doctor nor the patient knows who gets what. This means doctors cannot influence the results, avoiding any bias.
- The placebo is something that looks like the real drug but has no active ingredient. Using a placebo ensures the results are not biased or due to the placebo effect. Only the patients taking the real drug should see improvement in their symptoms.
After the drug has been tested it needs to be approved. The results and conclusions are peer reviewed- they are checked by other scientists.
Peer review is important to check conclusions are valid and that the results or claims are not biased.
Key Terms and Definitions
|
Term |
Definition |
|
Toxicity |
How harmful a drug is to the body. |
|
Efficacy |
How well the drug works. |
|
Placebo |
An inactive substance used in clinical trials. |
|
Double-blind trial |
Neither patient nor doctor know who gets the real drug. |
|
Peer review |
When results and conclusions are checked by other scientists. |
No answer provided.
Exam Tips
- Learn the examples on your specification of the following drugs and where they come from: aspirin, digitalis, and penicillin.
- Be ready to describe each stage of the drug development process and explain why the drug is tested on different groups in this order.
No answer provided.
Practice Question
The Ebola virus killed almost 10,000 people in Africa in 2014. Drug companies have developed and tested a new drug to treat Ebola.
Explain what testing must be done before this new drug can be used to treat people. (6 marks)
Model Answer:
- New drugs are first tested in preclinical trials on cells, tissues, and live animals to check for toxicity.
- If safe, clinical trials begin with very low doses on healthy volunteers to monitor for side effects.
- Later trials involve patients (e.g. with Ebola) to test for efficacy and find the optimum dose.
- A double-blind trial may be used, where some patients receive a placebo and neither patients nor doctors know who gets the real drug.
- Patients are randomly allocated to groups to reduce bias in the results.
- The results are peer reviewed to ensure they are reliable and to prevent false claims.
More Practice
Try to answer these practice questions from the TikTok videos on your own, then watch the videos to see how well you did!