Discovery and Development of Drugs
Practise Discovery and Development of Drugs for GCSE Biology with this free worksheet and full mark scheme — Foundation and Higher exam-style questions with worked answers for AQA, Edexcel and OCR. Know the stages of drug testing — preclinical testing followed by clinical trials — and terms such as placebo and double-blind.
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These worksheets and mark schemes are original, written for Virtus Academy and checked against the current AQA, Edexcel and OCR specifications. Every worksheet comes with a full mark scheme.
Topic overview
New drugs are extensively tested before they can be used, because they must be safe as well as effective.
Traditionally drugs came from plants and microorganisms — digitalis from foxgloves, aspirin from willow, and penicillin from the Penicillium mould discovered by Fleming. Most new drugs are now synthesised by chemists, though the starting point may still be a chemical from a plant.
Testing has three stages. Preclinical testing uses cells, tissues and live animals. Clinical trials then use healthy volunteers at very low doses to test for safety, before testing on patients to find the optimum dose. Double blind trials, where neither patient nor doctor knows who receives the placebo, remove bias from the results.
Revision notes
Where drugs come from
Digitalis, a heart drug, originates from foxgloves. Aspirin, used as a painkiller, originates from willow.
Penicillin was discovered by Alexander Fleming from the Penicillium mould. Most new drugs are now synthesised by chemists, though the starting point may be a plant chemical.
Preclinical and clinical testing
Preclinical testing is carried out in a laboratory using cells, tissues and live animals.
Clinical trials then use healthy volunteers first, at very low doses, to check the drug is safe. If it is, testing continues on patients to find the optimum dose.
Double blind trials and placebos
In a double blind trial, some patients receive a placebo — a treatment with no active drug.
Neither the patients nor the doctors know who has received which, which prevents expectations from influencing the results. Results are peer reviewed before publication to check for false claims.
Key points
- New drugs are tested for toxicity, efficacy and dose.
- Digitalis comes from foxgloves and aspirin from willow.
- Penicillin was discovered by Fleming from Penicillium mould.
- Preclinical testing uses cells, tissues and live animals.
- Clinical trials use healthy volunteers first, then patients.
- In a double blind trial neither patient nor doctor knows who has the placebo.
Worked examples
Example 1
Describe the three things a new drug is tested for. [3 marks]
Model answer
Toxicity, to check that it is not harmful (1 mark). Efficacy, to check that it works (1 mark). Dose, to find the optimum amount to give (1 mark).
Example 2
Explain why healthy volunteers are given very low doses at the start of clinical testing. [2 marks]
Model answer
The drug has not previously been tested on humans, so its effects are not fully known (1 mark). Using a very low dose reduces the risk of serious harm while the safety of the drug is assessed (1 mark).
Example 3
Explain why a double blind trial is used. [3 marks]
Model answer
Some patients are given a placebo containing no active drug (1 mark). Neither the patients nor the doctors know who has received the drug and who has the placebo (1 mark), so expectations cannot influence the results and the trial is not biased (1 mark).
Common mistakes
Saying drugs are tested only on animals.
Preclinical testing uses cells and tissues as well as live animals, and clinical trials use humans.
Giving patients the drug before healthy volunteers.
Healthy volunteers are tested first, at very low doses, to establish safety.
Confusing a placebo with a low dose.
A placebo contains no active drug at all.
Forgetting peer review.
Results are peer reviewed before publication to prevent false claims.
Exam tips
- Learn toxicity, efficacy and dose as the three testing aims.
- Give the testing stages in the correct order.
- Define a placebo precisely as containing no active drug.
- Mention that double blind removes bias.
Key terms
- Preclinical testing
- Laboratory testing on cells, tissues and live animals.
- Clinical trial
- Testing a drug on healthy volunteers and then patients.
- Placebo
- A treatment containing no active drug.
- Double blind trial
- A trial in which neither patient nor doctor knows who received the drug.
Related topics
Written and reviewed against the current AQA, Edexcel and OCR specifications. Spotted an error? Let us know.