4.3.4Unit 4: Energy, Environment, Microbiology and Immunity
Development of Drugs and Drug Testing — IAL Edexcel Linear Revision Notes & Topical Questions
5 min read 4 parts Lesson 20 of 28 Unit quiz
Part 1 of 4Early Drug Testing
New drugs must be tested for effectiveness and side effects before they are sold to the public.
Early Drug Testing
Clinical trials
- These tests protect the public from drugs that may pose a health risk.
Withering
- In the 1700s William Withering treated dropsy with foxglove extract, which contains the drug digitalis.
Variable doses
- Because foxglove is poisonous, he prepared remedies with different concentrations to find an effective, non-toxic one.
Contrast
- Early testing was not scientific or regulated like modern drug testing.
Part 2 of 4Modern Testing Sequence
A drug must pass each stage before moving to the next.
1
Computer models predict the likely effects of the drug.
2
The drug is tested on human tissues in the laboratory and then on animals.
3
Phase 1 trial: a small group of healthy volunteers shows how the body reacts, the side effects and the correct dosage.
4
Phase 2 trial: a larger group of patients who need the drug shows how effective it is.
5
Phase 3 trial: a large number of patients receive either the new drug or an existing drug to see whether the new one works better.
Part 3 of 4Reducing Bias
Trial design aims to remove the influence of expectations on the results.
Placebo
- A tablet that looks identical to the drug but contains no active ingredient, given to a control group.
Placebo effect
- Some patients improve simply because they believe they are receiving the drug.
Blinding
- Patients are not told which group they are in, so their expectations are the same across groups.
Double blind
- Neither patient nor doctor knows who receives the drug, which stops the doctor judging results differently.
When used
- Placebos are typically used in phase 2, and double-blind designs in phases 2 and 3.
Part 4 of 4Exam Checklist & Tips
4.3.4 – Key Points for the Exam
- Clinical trial A test of a new drug on human volunteers or patients.
- Placebo A treatment with no active ingredient that looks like the drug.
- Placebo effect Improvement caused by belief in treatment rather than the drug itself.
- Double blind A trial in which neither patient nor doctor knows who has the real drug.
- Dosage The amount of a drug taken and how often.
Common Mistakes
- Stating that phase 1 trials are on patients; they are normally on a small group of healthy individuals.
- Saying a placebo contains a weaker dose of the drug, when it contains no active ingredient.
- Confusing single-blind with double-blind designs.
- Missing out the computer modelling, tissue and animal testing that come before human trials.
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