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Where do new medicines come from, and how are they tested to be sure they are safe and effective?

The discovery of drugs from plants and microorganisms, the stages of developing and testing a new drug (preclinical testing and clinical trials), the use of placebos and double-blind trials, and why each stage is needed to check a drug is safe and effective.

A focused answer to the OCR Gateway GCSE Biology A topic B6 on drug development and testing, covering the discovery of drugs from plants and microorganisms, preclinical testing and clinical trials, the use of placebos and double-blind trials, and why each stage is needed to check a drug is safe and effective.

Generated by Claude Opus 4.89 min answer

Reviewed by: AI editorial process; not yet individually human-reviewed

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  1. What this dot point is asking
  2. Where drugs come from
  3. Why drugs must be tested
  4. Preclinical testing
  5. Clinical trials

What this dot point is asking

OCR wants you to describe where drugs are discovered, the stages of developing and testing a new drug (preclinical testing and clinical trials), the use of placebos and double-blind trials, and why each stage is needed to check a drug is safe and effective.

Where drugs come from

Historically, many useful drugs were discovered in plants and microorganisms, which make chemicals to defend themselves:

  • Digitalis, a heart drug, comes from the foxglove plant.
  • Aspirin, a painkiller, originates from a chemical in willow bark.
  • Penicillin, the first antibiotic, was discovered by Alexander Fleming from the Penicillium mould.

Today most new drugs are designed and made by scientists, often starting from a chemical found in nature and improving it, but the natural world is still an important source of new medicines, which is one reason maintaining biodiversity matters.

Why drugs must be tested

A new drug must be safe (not too toxic, with acceptable side effects) and effective (it does what it is meant to do) before patients can be given it. Testing also finds the optimum dose, the amount that works without causing unacceptable side effects. Drugs are therefore tested in stages, each one a check before the next.

Preclinical testing

This stage checks whether the drug works (efficacy), whether it is toxic (safety), and helps work out a safe starting dose. Testing on cells and tissues comes first; testing on animals follows, which raises ethical debate but is currently required by law before human trials.

Clinical trials

Two features make clinical trials reliable:

  • A placebo is a dummy treatment that looks like the drug but contains no active ingredient. Giving one group the placebo provides a control, so doctors can tell whether improvement is due to the drug rather than to patients simply expecting to get better (the placebo effect) or the illness passing on its own.
  • A double-blind trial is one where neither the patient nor the doctor knows who is getting the real drug or the placebo until the end. This removes bias, for example a doctor unconsciously treating or assessing the groups differently.

The results are checked by other scientists (peer review) before a drug is approved, to guard against false claims.

Exam-style practice questions

Practice questions written in the style of OCR exam questions on this dot point, with worked answer explainers. The year tag is the paper they imitate, not the source.

OCR 20186 marksDescribe the stages a new drug must pass through before it can be prescribed to patients, and explain why each main stage is needed.
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A 6-mark extended response, marked on an ordered account with reasons.

Preclinical testing: new drugs are first tested in the laboratory on cells and tissues, and then on animals, to check the drug works (efficacy), to look for toxicity, and to work out a safe starting dose. This stage is needed before any human is given the drug.

Clinical trials: the drug is then tested on humans. It is given first to a small number of healthy volunteers at very low doses to test for safety and side effects, then to patients with the illness to find the optimum dose and check it is effective. Trials often use a placebo and are double blind (neither patient nor doctor knows who has the real drug) so the results are not biased.

Reward the order (lab/cells, tissues, animals, then healthy volunteers, then patients), the reason for each stage (safety first, then dose and efficacy), and the use of placebo or double-blind testing to keep results reliable.

OCR 20214 marksIn a clinical trial, explain why some patients are given a placebo, and why a trial is often double blind.
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A B6 question on trial design.

Placebo: a placebo is a dummy treatment with no active drug. Giving one group a placebo provides a comparison (a control), so doctors can tell whether any improvement is due to the drug itself rather than the patients simply expecting to get better (the placebo effect) or the illness passing on its own.

Double blind: in a double-blind trial neither the patient nor the doctor knows who is receiving the real drug or the placebo. This prevents bias, for example a doctor unconsciously treating or assessing the two groups differently, or patients reporting differently if they knew which they had. Reward the placebo as a control against the placebo effect, and double-blind as a way to remove bias from both patient and doctor.

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