GCSE Biology revision

Discovery and development of drugs

Communicable diseases

AQA 4.1.1.1

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AQA student objectives

Learning pathway

All · Most · Some

ALL 🎯

Identify and describe Natural Sources of Drugs, Key Criteria When Testing Drugs and Stage 1: Testing on Cells and Tissues in the context of discovery and development of drugs.

MOST 🎯🎯

Explain the relationships between Natural Sources of Drugs, Key Criteria When Testing Drugs and Stage 1: Testing on Cells and Tissues and how they contribute to discovery and development of drugs.

SOME 🎯🎯🎯

Apply and analyse knowledge of Natural Sources of Drugs, Key Criteria When Testing Drugs and Stage 1: Testing on Cells and Tissues to interpret unfamiliar information about discovery and development of drugs.

Revision summary

Key knowledge

Read on screen, then print for Cornell-style active revision.

Natural Sources of Drugs

Many medicines are derived from substances produced by plants and microorganisms that have evolved over millions of years.
Aspirin, a common painkiller and fever reducer, was originally developed from a chemical found in the bark of willow trees.
Digitalis, used to treat heart conditions such as heart failure, was originally derived from a chemical found in foxglove plants.
Penicillin, the world's first and most widely used antibiotic, was discovered by Alexander Fleming when he noticed a fungus (Penicillium) killing surrounding bacteria in a petri dish.

1. Natural Sources of DrugsAQA

Notes

Many medicines are derived from substances produced by plants and microorganisms that have evolved over millions of years.
Aspirin, a common painkiller and fever reducer, was originally developed from a chemical found in the bark of willow trees.
Digitalis, used to treat heart conditions such as heart failure, was originally derived from a chemical found in foxglove plants.
Penicillin, the world's first and most widely used antibiotic, was discovered by Alexander Fleming when he noticed a fungus (Penicillium) killing surrounding bacteria in a petri dish.

Key Criteria When Testing Drugs

Efficacy refers to how well a drug produces its desired effect, such as how effectively an antibiotic kills bacteria.
Toxicity describes how harmful a drug is to the body, including any damage to cells or unwanted side effects.
Dosage refers to the amount or concentration of a drug that should be given to a patient.
Generally, a higher dose increases efficacy but also increases the risk of side effects, so finding the right balance is essential.

2. Key Criteria When Testing DrugsAQA

Notes

Efficacy refers to how well a drug produces its desired effect, such as how effectively an antibiotic kills bacteria.
Toxicity describes how harmful a drug is to the body, including any damage to cells or unwanted side effects.
Dosage refers to the amount or concentration of a drug that should be given to a patient.
Generally, a higher dose increases efficacy but also increases the risk of side effects, so finding the right balance is essential.

Stage 1: Testing on Cells and Tissues

In the first stage of drug testing, substances are tested on human cells and tissues grown in a laboratory.
This stage is beneficial because it allows large numbers of substances to be tested quickly and cheaply.
A limitation of this stage is that it does not reveal how the substance would affect a whole organism or a specific organ.

3. Stage 1: Testing on Cells and TissuesAQA

Notes

In the first stage of drug testing, substances are tested on human cells and tissues grown in a laboratory.
This stage is beneficial because it allows large numbers of substances to be tested quickly and cheaply.
A limitation of this stage is that it does not reveal how the substance would affect a whole organism or a specific organ.

Stage 2: Pre-Clinical Testing on Animals

If a substance shows promise in cell and tissue tests, it progresses to testing on live animals such as mice and rabbits.
In the UK, all drugs must be tested on at least two different types of live mammals before moving to human trials.
Because humans are also mammals, animal testing provides useful information about the efficacy and toxicity of a substance.
Stages 1 and 2 are collectively known as pre-clinical testing, as they do not involve human participants.

4. Stage 2: Pre-Clinical Testing on AnimalsAQA

Notes

If a substance shows promise in cell and tissue tests, it progresses to testing on live animals such as mice and rabbits.
In the UK, all drugs must be tested on at least two different types of live mammals before moving to human trials.
Because humans are also mammals, animal testing provides useful information about the efficacy and toxicity of a substance.
Stages 1 and 2 are collectively known as pre-clinical testing, as they do not involve human participants.

Stage 3: Clinical Testing — Healthy Volunteers

Clinical testing is the final stage of drug development and involves giving the drug to human participants for the first time.
The drug is first given to healthy volunteers at a very low dose to check for any immediate harmful effects.
The dose is gradually increased while doctors closely monitor the volunteers for side effects.
The aim at this step is to identify the maximum dosage that can be given before significant side effects occur.

5. Stage 3: Clinical Testing — Healthy VolunteersAQA

Notes

Clinical testing is the final stage of drug development and involves giving the drug to human participants for the first time.
The drug is first given to healthy volunteers at a very low dose to check for any immediate harmful effects.
The dose is gradually increased while doctors closely monitor the volunteers for side effects.
The aim at this step is to identify the maximum dosage that can be given before significant side effects occur.

Stage 3: Clinical Testing — Patient Trials

Once safety in healthy volunteers is established, the drug is given to patients suffering from the illness the drug is designed to treat.
The dose is again increased gradually, this time to find the optimum dosage where efficacy is maximised and toxicity is minimised.

Placebos and Blind Trials

A placebo is a substance that looks identical to the real drug but contains no active medication, often made from sugar.
In a blind trial, half of the volunteers receive the real drug and the other half receive the placebo, but participants are not told which they have been given.
This prevents volunteers from unconsciously reporting more side effects simply because they know they are taking the real drug.
In a double-blind trial, neither the volunteers nor the doctors know who has received the drug or the placebo until all results have been analysed.
Double-blind trials are the most reliable method as they eliminate unconscious bias from both patients and medical staff.

7. Placebos and Blind TrialsAQA

Notes

A placebo is a substance that looks identical to the real drug but contains no active medication, often made from sugar.
In a blind trial, half of the volunteers receive the real drug and the other half receive the placebo, but participants are not told which they have been given.
This prevents volunteers from unconsciously reporting more side effects simply because they know they are taking the real drug.
In a double-blind trial, neither the volunteers nor the doctors know who has received the drug or the placebo until all results have been analysed.
Double-blind trials are the most reliable method as they eliminate unconscious bias from both patients and medical staff.

Why Blind Trials Ensure Valid Results

Blind and double-blind trial designs ensure that the results of clinical testing are fair and free from bias.
Without blinding, doctors might be more likely to notice or record side effects in patients they know are taking the real drug, skewing the results.
Using a placebo as a control group allows scientists to compare the true effect of the drug against no treatment.

8. Why Blind Trials Ensure Valid ResultsAQA

Notes

Blind and double-blind trial designs ensure that the results of clinical testing are fair and free from bias.
Without blinding, doctors might be more likely to notice or record side effects in patients they know are taking the real drug, skewing the results.
Using a placebo as a control group allows scientists to compare the true effect of the drug against no treatment.

Peer Review

Once drug testing is complete, the results are written up and submitted for peer review, where other scientists analyse the methods and findings.
Peer review is a critical part of the scientific process as it helps to prevent false claims or flawed results from being published.
This rigorous scrutiny by independent scientists ensures that only reliable and valid drug testing data is accepted by the scientific community.

9. Peer ReviewAQA

Notes

Once drug testing is complete, the results are written up and submitted for peer review, where other scientists analyse the methods and findings.
Peer review is a critical part of the scientific process as it helps to prevent false claims or flawed results from being published.
This rigorous scrutiny by independent scientists ensures that only reliable and valid drug testing data is accepted by the scientific community.