GCSE · Biology · AQA · Spec 8461

Discovery and development of drugs

Foxgloves gave us a heart drug, willow a painkiller, a mould penicillin. A brand-new drug has to prove itself step by step first. What are the steps?

The testing route for a new drug

Before you open a stage, say what you think it checks: is the drug safe, does it work, or what dose is best? Then tap to see.

Biology · Where drugs come from

Plant, mould or chemist?

Before a drug can be tested, it has to come from somewhere. Pick a drug, then put it where it came from.

Still to sort

Extracted from a plant (0)

A traditional source: the drug originates in a plant.

From a microorganism (0)

The other traditional source, alongside plants.

Synthesised by chemists (0)

Made by chemists in the pharmaceutical industry.

Where the line is: A drug can land here even if its starting point was a chemical extracted from a plant. What puts it in this column is that chemists synthesise it.

4 of 4 still to sort.

Two words that get swapped

ToxicityvsEfficacy

The testing route kept asking 'is it safe?' and 'does it work?'. Scientists have a word for each question.

Focus

The question it answers

Toxicity

Is the drug safe?

Efficacy

Does the drug work?

The insight

Two separate questions, which is why a new drug is tested for both.

The everyday word hiding inside

Toxicity

toxic: harmful

Efficacy

effective: it does the job

Its part in the optimum dose

Toxicity

the safety side of the balance

Efficacy

the 'how well it works' side of the balance

Biology · Double blind trials

What does 'double blind' really mean?

A new drug is being trialled on patients. Some of them are given the new drug, and some are given a placebo. The trial is double blind.

Which is closest to what you think right now?

The patients don't know whether they're getting the real drug or the placebo. That's what makes it blind.The placebo is a weaker dose of the new drug, so it works a little bit.Neither the doctors nor the patients know who is getting the placebo.The doctors need to know who has the placebo, so they can keep the trial fair.

How sure are you?

I'm sureI think soI'm guessing

The patients don't know whether they're getting the real drug or the placebo. That's what makes it blind.

This is a common misconception

That's only one side, which is why it's called DOUBLE blind. The doctors don't know either. Neither the doctors nor the patients know who is receiving the placebo.

The placebo is a weaker dose of the new drug, so it works a little bit.

This is a common misconception

A placebo isn't the drug at all. It looks like the real drug but has no therapeutic effect.

Neither the doctors nor the patients know who is getting the placebo.

This matches the evidence

Exactly. 'Double' means both sides are kept in the dark, and that stops bias from either the doctors or the patients affecting the results.

The doctors need to know who has the placebo, so they can keep the trial fair.

This is a common misconception

It works the other way round. Keeping the doctors from knowing is part of what stops bias affecting the results. In a double blind trial, the doctors don't know who is receiving the placebo.

Placebo: looks like the real drug, has no therapeutic effect. Double blind: neither the doctors nor the patients know who is receiving it, so bias from either side can't affect the results.

Biology · Your turn to describe

Write it, then check it

A pharmaceutical company has synthesised a new medicine, Drug Q. Describe how Drug Q will be tested before it can be used. [6 marks]

Your answer

0 words · your answer stays on this page and is not sent anywhere.

The mark scheme

Preclinical testing in a lab (1 mark)
using cells, tissues and live animals (1 mark)
checking toxicity and efficacy (1 mark)
Clinical trials on healthy volunteers, very low doses, checking safety (1 mark)
Then patients with the illness, checking safety and effectiveness (1 mark)
If safe, more trials to find the optimum dose (1 mark)

Model answer

Drug Q goes through preclinical testing in a lab, on cells, tissues and live animals, to check its toxicity and efficacy. Clinical trials follow. Healthy volunteers take very low doses so its safety can be checked. Then patients with the illness take it, to check safety and effectiveness. If Drug Q proves safe, more trials find the optimum dose, balancing efficacy against toxicity.

Every stage earns its own credit, so keep them in sequence and name two things each time: who or what takes the drug, and what gets checked. The group most often missed is the healthy volunteers.

UK note

In AQA GCSE Biology, discovery and development of drugs is part of Infection and response, which is assessed on Paper 1.

WHAT YOU'VE LEARNED

A quick recap of today's lesson.

Where medicines come from, and the careful order a new one is tested in before anyone relies on it.

What you need to know

Traditionally, drugs were extracted from plants and microorganisms: digitalis (a heart drug) from foxgloves, aspirin (a painkiller) from willow, and penicillin, discovered by Alexander Fleming from the Penicillium mould.
Most new drugs are synthesised by chemists in the pharmaceutical industry, but the starting point may still be a chemical extracted from a plant.
New drugs are tested for toxicity (is it safe?), efficacy (does it work?) and dose.
Preclinical testing is done in a laboratory on cells, tissues and live animals. Clinical trials then use healthy volunteers at very low doses to check safety, then patients with the illness to check safety and effectiveness.
If the drug is found to be safe, further clinical trials find the optimum dose. In double blind trials some patients get a placebo, and neither the doctors nor the patients know who.

The big picture

Drugs were traditionally extracted from plants and microorganisms: digitalis from foxgloves, aspirin from willow, and penicillin, which Alexander Fleming discovered from the Penicillium mould. Most new drugs are now synthesised by chemists, sometimes starting from a plant chemical. Every new drug is tested for toxicity, efficacy and dose: preclinical testing in a lab on cells, tissues and live animals, then clinical trials on healthy volunteers at very low doses, then on patients, then, if it is safe, trials to find the optimum dose. Double blind trials with a placebo stop bias affecting the results.

Key points

1Plants and microorganisms were the traditional sources of drugs; most new drugs are now synthesised by chemists.

2Toxicity is whether a drug is safe; efficacy is whether it works.

3The testing order: preclinical (lab: cells, tissues, live animals), then healthy volunteers on very low doses, then patients, then the optimum dose.

4The optimum dose balances how well the drug works against its toxicity, and it's only looked for once the drug is found to be safe.

5A placebo looks like the real drug but has no therapeutic effect. Double blind means neither doctors nor patients know who gets it, which stops bias.

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Worked example

Problem

A company has a new drug that has just passed preclinical testing. A manager suggests: "Let's skip ahead and give it to patients who have the illness straight away, at a full dose, to see if it works." Explain what is wrong with this plan.

⚠ Watch out

Thinking a new drug goes straight to people who are ill. After the lab, it goes first to healthy volunteers on very low doses to check safety. Patients with the illness come after that.

🧠

Memory hook

Lab first. Healthy before ill. Safe before dose. And 'double blind' means both sides are blind: the doctors and the patients.

✓

Check yourself

Cover the page. For each testing stage, say who or what gets the drug, and whether that stage checks safety, whether it works, or the dose. Then define 'double blind' in one sentence.

Flashcards

(14)

What were the two traditional sources of drugs?

Plants and microorganisms.

Digitalis: what kind of drug, and where does it originate?

A heart drug. It originates from foxgloves.

Aspirin: what kind of drug, and where does it originate?

A painkiller. It originates from willow.

Who discovered penicillin, and from what?

Alexander Fleming, from the Penicillium mould.

How are most new drugs made today?

They are synthesised by chemists in the pharmaceutical industry. The starting point may still be a chemical extracted from a plant.

Why must new drugs be tested and trialled before use?

To check that they are safe and effective.

Toxicity

Whether the drug is safe.

Efficacy

Whether the drug works.

Where is preclinical testing done, and on what?

In a laboratory, on cells, tissues and live animals.

Who is first given a new drug in a clinical trial, and how much?

Healthy volunteers, on very low doses, to check the drug's safety.

Patients who have the illness: what does their trial check?

Both things: whether the drug is safe, and whether it is effective.

Optimum dose

The dose that balances how well the drug works against its toxicity. It's found in further trials once the drug is known to be safe.

Placebo

Something that looks like the real drug but has no therapeutic effect.

Double blind trial

Neither the doctors nor the patients know who is receiving the placebo, which stops bias from either side affecting the results.

Tap any card to flip it, or use Study as deck to go through them one at a time. In the full lesson these run as a spaced-repetition deck — you rate each card Hard, Good or Easy and the tricky ones keep coming back until they stick.

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Plant, mould or chemist?

What does 'double blind' really mean?

Write it, then check it

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